A revised classification of the Carboniferous and Permian Nautilida

1 European Journal of Taxonomy 1017: 1–85 https://doi.org/10.5852/ejt.2025.1017.3065 europeanjournaloftaxonomy.eu ISSN 2118-9773 2025 · Korn D. This work is licensed under a Creative Commons Attribution License (CC BY 4.0) Received: 25 September 2024 • Accepted: 7 April 2025 • Published: 24 September 2025 Topic editor: Marie-Béatrice Forel • Desk editor: Kristiaan Hoedemakers Monograph urn:lsid:zoobank.org:pub:BFD619DA-1648-440D-BF28-4BF0724CA6A0 A revised classification of the Carboniferous and Permian Nautilida Dieter KORN Museum für Naturkunde, Leibniz Institut for Research on Evolution and Biodiversity, Invalidenstraße 43, 10115 Berlin, Germany. Email: dieter[email protected] Abstract. Classification schemes for the Carboniferous and Permian coiled nautiloids were controversially discussed between the 1940s and the 1980s, but have rarely been a topic in the palaeontological literature since then. Depending on the respective affiliation of the authors with regard to their research base, either the Treatise on Invertebrate Paleontology or the Osnovy Paleontologii schemes were used. New findings from the last 40 years now make it possible to draw a more differentiated picture of the phylogeny and thus classification of the Nautilida. A new classification scheme is presented here, which is based on the integration of as many characters as possible, such as the general conch shape and its ontogeny, the shell sculpture and the shape of the septum and the course of the suture line. In addition, the stratigraphic succession of species and genera was taken into account. In the new classification presented here, seven suborders are distinguished within the order Nautilida, five of which known from Carboniferous and Permian strata. These are the Temnocheilina Flower, 1963 (superfamilies Trigonoceratoidea Hyatt, 1884, Koninckioceratoidea Hyatt, 1900), Domatoceratina subordo nov. (superfamilies Grypoceratoidea Hyatt, 1900, Permoceratoidea Miller & Collinson, 1953 and Subclymenioidea Shimansky, 1962), Tainoceratina Shimansky, 1957 (superfamilies Tainoceratoidea Hyatt, 1883 and Pleuronautiloidea Hyatt, 1900), Liroceratina Flower, 1955 (superfamilies Liroceratoidea Hyatt, 1900, Ephippioceratoidea Miller & Youngquist, 1949 and Clydonautiloidea Hyatt, 1900) and Solenochilina Flower, 1950 (superfamilies Aipoceratoidea Hyatt, 1884 and Scyphoceratoidea Ruzhencev & Shimansky, 1954). The new families and subfamilies Dasbergoceratidae fam. nov., Epistroboceratidae fam. nov., Stenopoceratidae fam. nov., Foordiceratidae fam. nov., Metacoceratidae fam. nov., Planetoceratidae fam. nov., Chouteauoceratinae subfam. nov. and Vestinautilinae subfam. nov. are introduced. Keywords. Nautiloidea, Nautilida, Carboniferous, Permian, classification. Korn D. 2025. A revised classification of the Carboniferous and Permian Nautilida. European Journal of Taxonomy 1017: 1–85. https://doi.org/10.5852/ejt.2025.1017.3065 Introduction Problems in the classification of coiled nautiloids Carboniferous and Permian coiled nautiloids have been described for more than 200 years (e.g., Sowerby 1812–1815, 1823–1825) (Fig. 1). However, classification schemes for these cephalopods European Journal of Taxonomy 1017: 1–85 (2025) 2 (order Nautilida Agassiz, 1847) have mainly been developed from the 1950s to the 1980s and have not been intensively discussed over the last 40 years. Therefore, there is no general agreement on the systematics of the group. The main reason for this situation is probably that the Late Palaeozoic coiled nautiloids are a less intensively studied fossil group compared to their distant ammonoid relatives. A new count of the Carboniferous and Permian taxa that have been described so far indicates a much lower diversity of nautiloids; about 960 species in about 150 genera have been described from these two periods. This compares with more than 3000 species of ammonoids (Korn & Ilg 2007 and additional data) for the same periods. Furthermore, the counts show that the diversity of the Carboniferous and Permian coiled nautiloids shows significant temporal fluctuations; about 340 species are known from the Early Carboniferous (Mississippian), about 210 species from the Late Carboniferous (Pennsylvanian), about 170 species from the Early Permian (Cisuralian), about 50 species from the Middle Permian (Guadalupian) and about 190 species from the Late Permian (Lopingian). They belong to 30 families (Fig. 2). Coiled nautiloids have often been recorded together with ammonoids in Carboniferous and Permian fossil assemblages. However, the co-occurrence of the two cephalopod groups must be seen as a small overlap zone, with nautiloids preferring the comparatively shallower areas of the shelf seas and ammonoids the deeper ones. In fossil collections from deeper shelf sediments, nautiloids have often been regarded as a by-product (or ‘bycatch’). Due to their rarity and apparently slow morphological evolution, they were usually not considered as index fossils and thus often went unnoticed. Perhaps for these reasons, taxonomic research has developed much slower on nautiloids than on ammonoids. While the ammonoids have undergone considerable changes in systematic classification over the last 100 years, including a prominent increase in the number of new higher taxa (suborders, superfamilies, families) as well as genera, there have been comparatively few changes in the nautiloids when considering taxa above the rank of genus. Classification schemes for the Carboniferous and Permian coiled nautiloids have been published several times (e.g., Flower & Kummel 1950; Kummel 1953, 1964; Shimansky 1957, 1962, 1967, 1979; Dzik 1984; King 1993), but they reveal great differences. There are several reasons for this: (1) General rarity of the study material. – Nautiloids are usually much rarer than, e.g., ammonoids at most localities. Therefore, the possibilities to describe specimens and to characterise species are Fig. 1. Reproductions of two of the first ever described and illustrated Carboniferous nautiloids. A. Aphelaeceras discus (Sowerby, 1813), from Sowerby (1812–1815). B. Vestinautilus cariniferus (Sowerby, 1824), from Sowerby (1823–1825). KORN D., A revised classification of the Carboniferous and Permian Nautilida 3 Fig. 2. The stratigraphic range of the families of Carboniferous and Permian coiled nautiloids. European Journal of Taxonomy 1017: 1–85 (2025) 4 much lower. Many species of Carboniferous and Permian coiled nautiloids are known from a single specimen only. Estimates of intraspecific variation are therefore rarely possible. (2) Unfavourable preservation of many specimens. – Coiled nautiloids in very good preservation are known from only a few localities. The best example is probably the occurrence of Early Permian cephalopods in the South Urals (Ruzhencev & Shimansky 1954), where the first whorl is often well preserved, allowing the study of early ontogeny. Many other localities, preferably representing shallower water sediments, often yield only specimens lacking a preserved first whorl. And even if the first whorl is preserved, mechanical preparation usually does not allow extraction. (3) Low number of species-specific characters. – Nautiloids usually offer relatively few conch characters to study. There is a variety of conch geometries and sculptures, but most Late Palaeozoic species have a very simple, concavely curved septal surface. Suture lines are therefore usually not suitable for distinguishing phylogenetic units. The suture line is usually determined by the shape of the whorl profile; flattened or concave areas of the whorl profile result in lobes. In addition, nautiloids tend to have only a few volutions, making ontogenetic trajectories of conch geometry difficult to analyse. (4) Poorly developed methodology for systematic descriptions. – In contrast to the study of ammonoids, there has been little use of quantitative methods in the study of coiled nautiloids. For example, cross sections of conchs to study ontogenetic development have very rarely been made, and rigorous morphometric methods to analyse adult conchs have not been carried out on a large scale. (5) Different personal views of authors. – There are differences between the various nautiloid researchers in the evaluation of certain characters, particularly when it comes to reconstructing the phylogeny and justifying the resulting classification schemes. However, it should be noted that the classification, initially based primarily on the shape of the adult conch, has been replaced over time by a subdivision that also includes internal characters, such as the shape and sculpture of the juvenile conch. Flower (1963: 94), with some frustration but not without humour, summed up the state of taxonomic study of coiled nautiloids at that time with a metaphor: “Probably anyone attempting revisionary investigation of relationship and the shaping of an appropriate taxonomy finds himself, like the man who put the clock together, with a few wheels left over.” Sixty years later, the situation has improved considerably in many areas. Knowledge of fossil nautiloids has been greatly enhanced by the monographic description of many new occurrences. As a result, the phylogenetic scheme and the possibility of classification have improved considerably. Nevertheless, there are still large gaps in our knowledge, reflected in the lack of potential intermediates. A new classification scheme for Carboniferous and Permian coiled nautiloids is presented here. This scheme attempts to take into account all available conch and sculpture parameters. Also integrated in this scheme is the stratigraphic succession of the taxa, although to a much lesser extent than the morphological features. Previous classification schemes The classification schemes of the Carboniferous and Permian coiled nautiloids vary greatly from author to author. A first scheme developed by Hyatt (1883–1884, 1891, 1898, 1900) of the group that he called Order Nautiloidea consisted of the suborders Holochoanites Hyatt, 1898, Mixochoanites Hyatt, 1898, Schizochoanites Hyatt, 1898, Orthochoanites Hyatt, 1898 and Cyrtochoanites Hyatt, 1898. The Orthochoanites included the units (which were not explicitly called superfamilies) Orthoceratida Hyatt, 1900 (with three families), Plectoceratida Hyatt, 1900 (five families), Pleuronautilida Hyatt, 1900 (two families), Ryticeratida Hyatt, 1900 (two families), Rhadinoceratida Hyatt, 1900 (four families), Hercoceratida Hyatt, 1900 (four families), Koninckioceratida Hyatt, 1900 (two families) and Digonoceratida Hyatt, 1900 (two families). The Carboniferous and Permian coiled nautiloids are distributed among several of these KORN D., A revised classification of the Carboniferous and Permian Nautilida 5 units. Regarding the classification scheme of Hyatt (1898, 1900), it should be noted that at that time the knowledge of the Early Carboniferous nautiloids was already quite good because of some monographs (de Koninck 1844, 1878; M‘Coy 1844), but much less was known about the Late Carboniferous and particularly Permian nautiloids, of which only a few species were known. In the first half of the 20th century, only minor modifications were proposed in a series of papers by Arthur K. Miller (e.g., Miller et al. 1933; Miller & Unklesbay 1942; Miller & Youngquist 1949), but in the second half of the 20th century, several competing phylogenetic reconstructions and hence classification schemes for the Carboniferous and Permian nautiloids were developed: Flower & Kummel (1950). – In the first comprehensive presentation of the systematics of all nautiloids, Flower & Kummel (1950) distinguished a total of 14 orders, four of which correspond to the order Nautilida as used today: Nautilida Agassiz, 1847 (ten families; Carboniferous to Recent), Solenochilida Flower, 1950 (one family; Carboniferous to Permian), Rutoceratida Flower, 1950 (four families; Devonian to Triassic) and Centroceratida Flower, 1950 (four families; Carboniferous to Triassic). Possible phylogenetic relationships between these were only vaguely presented, but the four orders are said to have originated in the family Barrandeoceratidae Foerste, 1925. Flower & Kummel (1950) did not use the taxonomic categories of superfamily and suborder. Kummel (1953, 1964). – In his contribution to the Treatise of Invertebrate Paleontology, Kummel (1964) took a much more conservative approach, which was based on his earlier monograph on the Triassic nautiloids (Kummel 1953). Kummel (1964) did not distinguish any suborders within the order Nautilida. Instead, he accepted the five superfamilies Aipocerataceae Hyatt, 1883, Tainocerataceae Hyatt, 1883, Trigonocerataceae Hyatt, 1884, Clydonautilaceae Hyatt, 1900 and Nautilaceae de Blainville, 1825. Although this scheme differs in some respects from that published by Shimansky (1957), there are many similarities. These superfamilies correspond in several respects to the suborders distinguished by Shimansky (1957). It is not clear on what morphological ground the classification scheme proposed by Kummel (1964) was based, as the text discussing the phylogeny mainly contains information about the differences between the groups in terms of adult conchs. It was therefore a narrative of the hypothetical relationships between the groups rather than an analytical approach. This resulted in very similar and sometimes uninformative definitions of superfamilies and families, with no clear statements on the plesiomorphic and apomorphic characters of individual higher taxa. Ruzhencev & Shimansky (1954), Shimansky (1957, 1962, 1967, 1979). – Based on excellently preserved Early Permian material from the South Urals, Ruzhencev & Shimansky (1954) provided an extensive discussion of the phylogeny of all Permian nautiloids. They used a wide range of characters for their classification scheme, which was intended to reflect the phylogenetic relationships of the taxa within the group. Most importantly, it included the morphology of juvenile conchs, which had not played a major role in previous studies. This scheme, which differed significantly from that previously outlined by Miller & Youngquist (1949), was subsequently developed (Shimansky 1957) and detailed in the Osnovy Paleontologii (Shimansky 1962). In this scheme, the order Nautilida Agassiz, 1847 consisted of the five suborders Rutoceratina Flower, 1950 (two superfamilies; Devonian to Permian), Tainoceratina Shimansky, 1957 (four superfamilies; Devonian to Triassic), Centroceratina Flower, 1950 (two superfamilies; Devonian to Triassic), Liroceratina Flower, 1955 (two superfamilies; Devonian to Cretaceous) and Nautilina Agassiz, 1847 (two superfamilies; Triassic to Recent). This scheme recognised that the first four suborders originated in the Devonian. The phylogenetic diagram shown by Shimansky (1957) is remarkable for its geometry, showing 13 long lineages, typically representing families, for the Carboniferous and Permian periods. There is only one European Journal of Taxonomy 1017: 1–85 (2025) 6 superfamily (Rhiphaeocerataceae Ruzhencev & Shimansky, 1954) with two families that first appeared in the Permian. The order Rutoceratina was considered to be the ancestral root of all post-Devonian coiled nautiloids. According to Shimansky, two lineages survived from the Devonian into the Carboniferous, namely the family Neptunoceratidae Shimansky, 1957 and the superfamily Solenochilaceae Hyatt, 1893. This scheme was then further modified by Shimansky (1967, 1979) to accept only three suborders within the order Nautilida: Rutoceratina (eight or nine superfamilies with a total of 21 families; Devonian to Triassic), Liroceratina (two superfamilies with five families, Carboniferous to Triassic) and Nautilina (two superfamilies with five families, Triassic to Recent). The phylogenetic scheme (Shimansky 1967: 49) shows the family Rutoceratidae Hyatt, 1884 as the ancestor of the Nautilida. Shevyrev (2006) used the same classification, but with the suborder names Rutocerina, Lirocerina and Nautilina. In his study and discussion of the phylogeny of the entire Nautiloidea, Dzik (1984) presented an alternative phylogenetic reconstruction for the post-Devonian coiled nautiloids. This attempt utilised a wide range of conch characters, including the juvenile morphology, but also the stratigraphic occurrence of the taxa discussed. The classification scheme of the order Nautilida shown by Dzik differs markedly from the previously published schemes. It contains the largely Palaeozoic suborders Centroceratina (Ordovician to Devonian), an “uncertain suborder” with the superfamily Aipoceratoidea Hyatt, 1884 (Devonian to Permian) and the very voluminous Tainoceratina Shimansky, 1957 (with the families Trigonoceratidae Hyatt, 1884, Phacoceratidae Shimansky, 1962, Tainoceratidae Hyatt, 1883, Grypoceratidae Hyatt, 1900, Clydonautilidae Hyatt, 1900, Syringonautilidae Mojsisovics, 1902 and Liroceratidae Miller & Youngquist, 1949; Carboniferous to Triassic). The third suborder Nautilina Agassiz, 1847 includes the post-Triassic nautiloids, as proposed in the phylogenetic schemes of Shimansky (1957) and Kummel (1964). Dzik (1984: 149) explicitly addressed the difficulties of distinguishing between taxa higher than the family level: “For practical purposes, I assign the Early Paleozoic nautiloids to the suborder Centroceratina, the Late Paleozoic and Triassic to the suborder Tainoceratina, and the post-Triassic species to the suborder Nautilina. These suborders cannot be unequivocally diagnosed because of frequent evolutionary convergence.” For comparison with the new classification scheme presented here, the three main historical classifications of the Nautilida are given here: “Osnovy Paleontologii” (Shimansky 1962): Order Nautilida Agassiz, 1847 Suborder Rutoceratina Flower, 1950 Superfamily Rutocerataceae Hyatt, 1884 Family Rutoceratidae Hyatt, 1884 Family Neptunoceratidae Shimansky, 1957 Superfamily Aipocerataceae Hyatt, 1884 Family Litogyroceratidae Shimansky, 1957 Family Scyphoceratidae Ruzhencev & Shimansky, 1954 Family Dentoceratidae Ruzhencev & Shimansky, 1954 Family Aipoceratidae Hyatt, 1884 Suborder Tainoceratina Shimansky, 1957 Superfamily Tainocerataceae Hyatt, 1883 Family Tetragonoceratidae Flower, 1945 Family Tainoceratidae Hyatt, 1883 Subfamily Tainoceratinae Hyatt, 1883 Subfamily Pleuronautilinae Hyatt, 1900 Family Mosquoceratidae Ruzhencev & Shimansky, 1954 KORN D., A revised classification of the Carboniferous and Permian Nautilida 7 Superfamily Encoilocerataceae Shimansky & Erlanger, 1955 Family Encoiloceratidae Shimansky & Erlanger, 1955 Superfamily Temnocheilaceae Mojsisovics, 1902 Family Temnocheilidae Mojsisovics, 1902 Family Gzheloceratidae Ruzhencev & Shimansky, 1954 Superfamily Rhiphaeocerataceae Ruzhencev & Shimansky, 1954 Family Rhiphaeoceratidae Ruzhencev & Shimansky, 1954 Family Aktubonautilidae Ruzhencev & Shimansky, 1954 Suborder Centroceratina Flower, 1950 Superfamily Trigonocerataceae Hyatt, 1884 Family Trigonoceratidae Hyatt, 1884 Subfamily Trigonoceratinae Hyatt, 1884 Subfamily Aphelaeceratinae Shimansky, 1962 Subfamily Thrincoceratinae Ruzhencev & Shimansky, 1954 Subfamily Knightoceratinae Shimansky, 1962 Family Subclymeniidae Shimansky, 1962 Family Phacoceratidae Shimansky, 1962 Superfamily Centrocerataceae Hyatt, 1900 Family Centroceratidae Hyatt, 1900 Family Grypoceratidae Hyatt, 1900 Subfamily Domatoceratinae Miller & Youngquist, 1949 Subfamily Grypoceratinae Hyatt, 1900 Subfamily Syringonautilinae Mojsisovics, 1902 Subfamily Clymenonautilinae Shimansky, 1962 Family Neothrincoceratidae Shimansky, 1962 Family Permoceratidae Miller & Collinson, 1953 Suborder Liroceratina Flower, 1955 Superfamily Lirocerataceae Miller & Youngquist, 1949 Family Liroceratidae Miller & Youngquist, 1949 Family Ephippioceratidae Miller & Youngquist, 1949 Family Koninckioceratidae Hyatt, 1900 Family Paranautilidae Kummel in Flower & Kummel, 1950 Superfamily Clydonautilaceae Hyatt, 1900 Family Clydonautilidae Hyatt, 1900 Family Gonionautilidae Kummel in Flower & Kummel, 1950 Family Siberonautilidae Popov, 1951 Family Pseudonautilidae Hyatt, 1900 Suborder Nautilina Agassiz, 1847 Superfamily Nautilaceae d’Orbigny, 1840 recte de Blainville, 1825 Family Nautilidae d’Orbigny, 1840 Subfamily Nautilinae d’Orbigny, 1840 Subfamily Pseudaganidinae Kummel, 1956 Family Cymatoceratidae Spath, 1927 Subfamily Cymatoceratinae Spath, 1927 Subfamily Heminautilinae Shimansky, 1962 Family Hercoglossiidae Spath, 1927 Superfamily Aturiaceae Hyatt, 1894 Family Aturiidae Hyatt, 1894 [recte Chapman, 1857] European Journal of Taxonomy 1017: 1–85 (2025) 8 “Treatise on Invertebrate Paleontology” (Kummel 1964): Order Nautilida Agassiz, 1847 Superfamily Tainocerataceae Hyatt, 1883 Family Tainoceratidae Hyatt, 1883 Family Rutoceratidae Hyatt, 1884 Family Tetragonoceratidae Flower, 1945 Family Rhiphaeoceratidae Ruzhencev & Shimansky, 1954 Family Koninckioceratidae Hyatt, 1900 Superfamily Trigonocerataceae Hyatt, 1884 Family Trigonoceratidae Hyatt, 1884 Family Centroceratidae Hyatt, 1900 Family Grypoceratidae Hyatt, 1900 Family Permoceratidae Miller & Collinson, 1953 Family Syringonautilidae Mojsisovics, 1902 Superfamily Aipocerataceae Hyatt, 1884 Family Aipoceratidae Hyatt, 1884 Family Solenochilidae Hyatt, 1893 Family Scyphoceratidae Ruzhencev & Shimansky, 1954 Superfamily Clydonautilaceae Hyatt, 1900 Family Clydonautilidae Hyatt, 1900 Family Liroceratidae Miller & Youngquist, 1949 Family Ephippioceratidae Miller & Youngquist, 1949 Family Gonionautilidae Kummel in Flower & Kummel, 1950 Family Siberonautilidae Popov, 1951 Superfamily Nautilaceae de Blainville, 1825 Family Nautilidae de Blainville, 1825 Family Pseudonautilidae Shimansky & Erlanger, 1955 Family Paracenoceratidae Spath, 1927 Family Cymatoceratidae Spath, 1927 Family Hercoglossiidae Spath, 1927 Family Aturiidae Chapman, 1857 “Phylogeny of the Nautiloidea” (Dzik 1984): Order Nautilida Agassiz, 1847 Suborder Centroceratina Flower, 1950 Family Uranoceratidae Hyatt, 1900 Family Lechritrochoceratidae Flower, 1950 Family Rhadinoceratidae Hyatt, 1900 Family Trochoceratidae Zittel, 1884 Suborder uncertain “Superfamily Aipoceratoidea Hyatt, 1884” Family Aipoceratidae Hyatt, 1883 Family Solenochilidae Hyatt, 1893 Suborder Tainoceratina Shimansky, 1957 Family Trigonoceratidae Hyatt, 1884 Family Phacoceratidae Shimansky, 1962 Family Tainoceratidae Hyatt, 1883 Family Grypoceratidae Hyatt, 1900 Family Clydonautilidae Hyatt, 1900 Family Syringonautilidae Mojsisovics, 1902 Family Liroceratidae Miller & Youngquist, 1949 KORN D., A revised classification of the Carboniferous and Permian Nautilida 9 Suborder Nautilina Agassiz, 1847 Family Paracenoceratidae Spath, 1927 Family Cymatoceratidae Spath, 1927 Family Nautilidae de Blainville, 1825 Family Aturiidae Chapman, 1857 Basics for a new systematic scheme for the Carboniferous and Permian nautiloids There is currently no generally accepted hierarchical character system for the structure of Late Palaeozoic coiled nautiloids. Comparison with ammonoids shows that the characters used to distinguish orders, families, genera and species are not clearly recognised in nautiloids. Regarding the classification schemes of coiled nautiloids, different approaches to the use of characters have been taken in recent decades. General conch morphology The external shape of the conch was considered the classic character for distinguishing the major units within the order Nautilida (e.g., Hyatt 1900; Flower & Kummel 1950). The main criteria were the degree of coiling (cyrtoconic, gyroconic or more or less tightly coiled), the degree of overlap upon the preceding whorl and the shape of the whorl profile. The general shape of the conch and the shape of the whorl profile in many phylogenetic lineages and taxonomic units of the Nautilida are stable characters that have changed slowly in the course of evolution. This is evident in genera with simple conch geometry, such as Domatoceras Hyatt, 1891 and Liroceras Teichert, 1940 as well as genera with more complex conch geometry, such as Tainoceras Hyatt, 1883, whose representatives have only slightly altered their conch shape over long geological timescales. On the other hand, there are cases where similar conch geometry does not necessarily reflect phylogenetic relationships. Such examples are the genera Permonautilus Kruglov, 1933 (Liroceratina) and Solenocheilus Hyatt, 1884 (Solenochilina Flower, 1950), both of which possess very conspicuous, long thorn-like processes on the umbilical wall of a pachyconic or globular adult conch. Taxa at various levels have often been characterised by changes of their conch morphology during ontogenetic development. However, these characterisations were usually vague and lack quantification, such as “conch rapidly increasing in width and height”. To improve clarity, descriptions in this format can be translated into the ratio of whorl width to whorl height and the whorl expansion rate (WER). The shape of the whorl profile, specifically the position of the ventrolateral shoulder and the umbilical margin, plays a crucial role in ontogenetic development of Early Carboniferous nautilids (Fig. 3). Phylogenetic reconstructions have to include this character. The evolution of the angular lateral margin can take four paths: remaining in a lateral or ventrolateral position (Fig. 3A, F) in the suborder Temnocheilina Flower, 1963, being replaced by a circular whorl profile, developing into an umbilical margin in the suborders Domatoceratina subordo nov. (Fig. 3B–C, G–H) and Tainoceratina Shimansky, 1957 (Fig. 3D, I), or evolving into both a ventrolateral shoulder and an umbilical margin (Fig. 3E, J) in the suborder Liroceratina Flower, 1955.. Juvenile conch morphology The morphology of the juvenile conch is an important criterion in differentiating high taxonomic units. The curvature of the first volution and the size of the umbilical foramen are key features that have not been consistently studied. Ruzhencev & Shimansky (1954) conducted a detailed study on the variation in juvenile development using well-preserved Early Permian material from the South Urals. Studies at many other sites have not been conducted due to either fragmented material or the inability to mechanically separate juvenile volutions. European Journal of Taxonomy 1017: 1–85 (2025) 16 with the Devonian family Centroceratidae Hyatt, 1900; according to this it had been derived from the family Rutoceratidae Hyatt, 1884. At the end of the Triassic, the suborder Centroceratina gave rise to the suborder Nautilina, which includes all Jurassic to Recent coiled nautiloids. According to the phylogenetic scheme outlined by Dzik (1984), all post-Devonian coiled nautiloids, with the exception of the aipoceratids, form a monophyletic unit with roots in the earliest Carboniferous. Dzik & Korn (1992) presented Dasbergoceras Dzik & Korn, 1992 as a possible ancestor of the Trigonoceratidae and thus the suborder Temnocheilina and with this the majority of post-Devonian coiled nautiloids. Dasbergoceras alternans (Tietze, 1871) has an advolute conch with a large umbilical foramen (27 mm) and a trapezoidal whorl profile. It possesses coarse radial ribs terminating in prominent conical nodes on the ventrolateral shoulder. The siphuncle is located close to the venter. Although this species shows some superficial resemblance to species of Temnocheilus, it can hardly be considered a direct ancestor; Temnocheilus was probably derived from Subvestinautilus Turner, 1954, as suggested by Dzik & Korn (1992: 88), and the ventrolateral row of nodes is considered a secondary character. The ancestry of the Temnocheilina, with or without Dasbergoceras included, is an unsolved problem because of several unanswered questions: (1) What was the morphological inventory of a possible ancestor of the Temnocheilina? – The characters of the almost central siphuncle and the ornamentation with spiral ridges in the early juvenile stage, which are important for the Temnocheilina, are not present in the Devonian nautilids, including Dasbergoceras. (2) Are the Temnocheilina derived from fully coiled or loosely coiled conchs? For example, does Trigonoceras M‘Coy, 1844 represent a plesiomorphic form or did the cyrtoconic conch arise by secondary uncoiling? – Intuition, based on knowledge of some other evolutionary lineages in cephalopods, would favour an evolutionary lineage from loosely coiled to fully coiled conchs. However, this observation in some of the groups may not apply in every individual case; some other cases of probable secondary uncoiling are known, for example in Maccoyoceras Miller, Dunbar & Condra, 1933 where the terminal whorl separates slightly from the preceding one (Foord 1900; Histon 1999). (3) Did the oldest representatives of the Temnocheilina undergo a rapid middle and late Tournaisian evolution after the Hangenberg Event at the Devonian–Carboniferous boundary, or was it a slow, long evolutionary process that started already in the Late Devonian, but was hidden without a fossil record? – The ‘nautiloid gap’ spanning most of the Late Devonian and the earliest Carboniferous with the only one known genus Dasbergoceras in the latest Devonian is the cardinal obstacle to answering this question. This is related to the general question of possible very different evolutionary rates in nautiloids. Phylogeny Gaps in our knowledge mean that the evolutionary pathways within the suborder Temnocheilina are, at least in part, unknown. Several questions concern the degree of involution of the conch, the shape of the whorl profile and the ornamentation: (1) Do the gyroconic conchs (e.g., Trigonoceras M‘Coy, 1844) represent the plesiomorphic state or are they the result of secondary uncoiling? – This is a difficult question to answer as there are only very fragmentary records of the stratigraphically oldest representatives. Moreover, openly coiled conchs are known from both the oldest known assemblages such as Chouteauoceras Miller & Garner, 1953 in early Late Tournaisian (Miller & Furnish 1939; Miller & Garner 1953) and from much younger assemblages such as Trigonoceras in the Viséan (Maillieux 1925). It is possible that both evolutionary paths, including increased coiling and also secondary uncoiling, were realised in KORN D., A revised classification of the Carboniferous and Permian Nautilida 17 these Early Carboniferous nautiloids. However, if a form like Dasbergoceras was the ancestor, then repeated cases of secondary uncoiling must be assumed. (2) Does the triangular (e.g., Trigonoceras M‘Coy, 1844, Triboloceras Hyatt, 1884), compressed oval (Chouteauoceras), or depressed ovate (e.g., Rineceras Hyatt, 1893) whorl profile represent the plesiomorphic condition? – Similar to the general conch shape, the evolutionary pathways of the whorl profile are also not fully understood. For example, in the proposed evolutionary lineage Triboloceras-Vestinautilus-Subvestinautilus, an evolutionary trend can be observed from angular triangular to more rounded triangular and trapezoidal whorl profiles. (3) Are coarse longitudinal ridges or more delicate spiral lines of the juvenile conch the plesiomorphic state? – Longitudinal ridges in the stratigraphically oldest known species have been reported from several Middle and early Late Tournaisian formations, including the Calcaire de Vaulx and Calonne in Belgium (de Koninck 1878), the Chouteau Formation in Missouri (Miller & Furnish 1939), the Marshall Sandstone in Michigan (Miller & Garner 1953) and the Argiles de Teguentour in central Algeria (Korn & Bockwinkel 2022). At the same time, the coarse spiral ornamentation of the earliest juvenile stage has been reported to have regressed in several species and genera. These records provide good evidence for the hypothesis that the longitudinal ridges represented a plesiomorphic state. In addition, the stratigraphic position of the material also suggests that in one derived evolutionary lineage (family Subclymeniidae Shimansky, 1962 of the suborder Domatoceratina subordo nov.) there was a phylogenetic change in the juvenile ornamentation from coarse spiral ridges (early Late Tournaisian) to fine spiral lines (latest Tournaisian) and finally to the loss of spiral ornamentation (Viséan). In others, the spiral ridges were reduced in number but became much coarser (family Epistroboceratidae fam. nov. of the suborder Domatoceratina) or were gradually reduced (e.g., Vestinautilinae subfam. nov. and Temnocheilidae Mojsisovics, 1902). Despite these partly unresolved problems, at least some possible phylogenetic lineages can be identified, which are also supported by stratigraphic data. A morphological transformation of the different conch characters can be observed: (1) General coiling. – Within the genera Rineceras and Vestinautilus there is an evolutionary trend towards increasingly dense coiling, which could be seen as a general trend among the early representatives of the Temnocheilina. (2) Whorl profile. – There is a trend from triangular to rounded trapezoidal shapes. This is related to the tighter enclosure of the preceding whorls. However, there is also a trend from an originally concave or at least strongly flattened venter to an increasingly convex rounded venter. (3) Sculpture. – A general trend can be seen in the decreasing strength of the spiral ridges. Such a trend affects, for example, the number and strength of spiral ridges, as can be seen in Vestinautilus and Subvestinautilus. Descendants According to the current state of knowledge, three further suborders can be derived from the Temnocheilina; these are the Domatoceratina subordo nov., the Tainoceratina and the Liroceratina. The first two are distinguished from the Temnocheilina by the more or less simultaneous early ontogenetic formation of an umbilical margin and a ventrolateral shoulder; the latter developed only an umbilical margin but no prominent ventrolateral shoulder. The demarcation of some of the genera (e.g., Catastroboceras Turner, 1965 and Epidomatoceras Turner, 1954) placed here in the Domatoceratina is sometimes difficult because it is not always clear whether they already possess an umbilical margin. However, this is formed by the reduction of the spiral ridges present in the early growth stage. The early ontogenetic stage of Tainoceratina, at least those from the Early Permian, apparently does not show a spiral ornament (Ruzhencev & Shimansky 1954). European Journal of Taxonomy 1017: 1–85 (2025) 18 Superfamily Trigonoceratoidea Hyatt, 1884 Figs 6–10 Diagnosis Superfamily of the suborder Temnocheilina, in which a ventrolateral shoulder is formed early in ontogeny. Conch gyroconic or advolute in some species, but more or less tightly coiled in most of the species; general conch form usually discoidal, subevolute or evolute. Whorl profile depressed elliptical or bicarinate in the initial growth stage of the early species and circular in the advanced species. Conch ontogeny with the widest area of the initial growth stage transforming into a pronounced ventrolateral shoulder. Adult whorl profile often rounded triangular but also rounded trapezoidal, polygonal or circular. Juvenile stage with longitudinal ridges or lines, which are particularly pronounced in the area of the venter and the ventrolateral shoulder of the adult stage. Septa simply domed. Suture line with shallow lobes and saddles; internal lobe absent or very shallow and rarely triangular. Included families Trigonoceratidae Hyatt, 1884 (Early Carboniferous to Early Permian; 13 genera, 72 species). Triboloceratidae Hyatt, 1884 [synonym of Trigonoceratidae]. Rineceratidae Hyatt, 1893 [synonym of Trigonoceratidae]. Rhineceratidae Hyatt, 1900 [nomen nullum, synonym of Trigonoceratidae]. Temnocheilidae Mojsisovics, 1902 (Early Carboniferous to Early Permian; 11 genera, 59 species). Thrincoceratidae Ruzhencev & Shimansky, 1954 (Early Carboniferous to Early Permian; 4 genera, 17 species). Knightoceratidae Shimansky, 1962 [synonym of Temnocheilidae]. Neothrincoceratidae Shimansky, 1962 [synonym of Thrincoceratidae]. Dasbergoceratidae fam. nov. (Late Devonian; 1 genus, 1 species). Remarks The superfamily Trigonoceratoidea probably originated in a genus similar to Dasbergoceras in the latest Famennian (Late Devonian). Along with the superfamily Aipoceratoidea, it is the second evolutionary lineage of coiled nautiloids to cross the Devonian-Carboniferous boundary (Dzik & Korn 1992). There Fig. 6. Representatives of the superfamily Trigonoceratoidea Hyatt, 1884. A. Family Temnocheilidae Mojsisovics, 1902. Endolobus spectabilis (Meek & Worthen, 1860), from Miller & Youngquist (1949). B. Family Trigonoceratidae Hyatt, 1884. Vestinautilus cariniformis (Sowerby, 1824), from Foord (1900). Scale bar units = 10 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 19 are as yet no records from the earliest Carboniferous period, the Gattendorfia Stufe in the traditional ammonoid stratigraphy. On the basis of current knowledge, it is likely that coiled nautiloids underwent rapid morphological evolution during the Middle Tournaisian, which may be the reason for the great conch and sculpture diversity in the Late Tournaisian. The adult conch shapes of the Trigonoceratoidea are diverse, ranging from cyrtoconic to subevolute; the latter being the dominant ones (Fig. 6). This is the reason why it is difficult to characterise the superfamily on the basis of the adult conch shape alone. The same is true for the ornamentation. In many species, there are more or less pronounced spiral ridges or spiral lines developed, but this can also be reduced in many advanced species. The course of the suture line is usually strongly dependent on the shape of the whorl profile. This is because the septum is usually uniformly concave in shape. For this reason, the ontogeny of conch shape and ornamentation is used here as a key character to distinguish families and subfamilies. Four families within the Trigonoceratoidea can be separated on the base of the following principal characters: Dasbergoceratidae fam. nov. – Ancestral taxa with a triangular whorl profile and a large umbilical foramen. Sculpture with short radial ribs ending in conical ventrolateral nodes. Siphuncle subcentral, close to the venter (Fig. 7). Trigonoceratidae. – Ancestral taxa with a wide variety of conch shapes ranging from cyrtoconic to more or less tightly coiled. Early juvenile whorl profile depressed oval. Internal lobe shallow, broadly rounded (Fig. 8). Thrincoceratidae. – Derived taxa with a usually evolute conch shape. Early juvenile whorl profile nearly circular. Internal lobe shallow, broadly rounded (Fig. 9). Temnocheilidae. – Derived taxa with a subevolute or evolute conch shape. Early juvenile whorl profile strongly depressed oval. Internal lobe deep, funnel-shaped or subtriangular (Fig. 10). The superfamily Trigonoceratoidea differs from the superfamily Koninckioceratoidea in the shape of the whorl profile, which is triangular or trapezoidal with a flat venter in the ancestral Trigonoceratoidea, but simply oval in the Koninckioceratoidea. In addition, the shell of the Trigonoceratoidea is decorated with coarse, long ridges, whereas that of the Koninckioceratoidea is almost smooth. Fig. 7. Family Dasbergoceratidae fam. nov. Dasbergoceras alternans (Tietze, 1871), from Dzik & Korn (1992). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 20 Fig. 8. Representatives of the subfamily Trigonoceratinae Hyatt, 1884; all from de Koninck (1880). A. Triboloceras consobrinum (de Koninck, 1880). B. Triboloceras serratum (de Koninck, 1844). C. Rineceras tesselatum (de Koninck, 1880). D. Rineceras propiquum (de Koninck, 1880). Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 21 Fig. 9. Family Thrincoceratidae Ruzhencev & Shimansky, 1954. Thrincoceras hyatti Foord, 1900, from Foord (1900). Scale bar units = 1 mm. Fig. 10. Family Temnocheilidae Mojsisovics, 1902. Temnocheilus coronatus (M‘Coy, 1844), from Foord (1900). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 22 Family Dasbergoceratidae fam. nov. urn:lsid:zoobank.org:act:D31465BD-72EB-43EE-B36E-4B9DEF64B0C3 Fig. 7 Type genus Dasbergoceras Dzik & Korn, 1992. Diagnosis Family of the superfamily Trigonoceratoidea with a subevolute conch with very small whorl overlap; large umbilical foramen. Whorl profile in the adult stage rounded trapezoidal and depressed oval in the early juvenile stage. Ornament with transverse ribs. Position of the siphuncle closer to the venter than to the centre. Suture line with broadly rounded shallow lobes and low saddles. Etymology The family name refers to the type genus. Included genus Dasbergoceras Dzik & Korn, 1992 (Famennian; 1 species). Remarks Dzik & Korn (1992) devoted a separate paper to the genus Dasbergoceras (Fig. 7), discussing the importance of this Late Devonian genus as a link between Devonian and Carboniferous curved and coiled nautiloids. Apparently, no other material has been described since. Therefore, the question of whether Dasbergoceras is a direct ancestor of the Carboniferous Trigonoceratoidea or whether it is a side branch of the Trigonoceratoidea cannot be answered unequivocally. Dasbergoceras has morphological peculiarities that distinguish it from all other genera of the Trigonoceratoidea. These include the subventrally located siphuncle and the radial ribbing. For this reason, an independent family Dasbergoceratidae fam. nov. is proposed here. Family Trigonoceratidae Hyatt, 1884 Diagnosis Family of the superfamily Trigonoceratoidea with cyrtoconic to subevolute conch with small whorl overlap if present; large or moderately large umbilical foramen. Whorl profile in the adult stage commonly ranging from triangular to depressed oval, rarely compressed oval or polygonal. Whorl profile usually depressed oval in the early juvenile stage. Ornament with longitudinal ridges or lines, rarely transverse ribs; sometimes the conch is smooth. Position of the siphuncle closer to the centre than to the ventral side. Suture line with broadly rounded shallow lobes and low saddles. Included subfamilies Trigonoceratinae Hyatt, 1884 (Early Carboniferous to Early Permian; 7 genera, 38 species). Chouteauoceratinae subfam. nov. (Early Carboniferous to ? Early Permian; 3 genera, 5 species). Vestinautilinae subfam. nov. (Early Carboniferous; 3 genera, 29 species). Remarks Flower & Kummel (1950: 615) combined the families Triboloceratidae, Trigonoceratidae and Rineceratidae of Hyatt and gave priority to the first of these. Following the idea of Shimansky (1962), the family Trigonoceratidae is divided into several subfamilies here, which differ in the following morphological characteristics: Trigonoceratinae. – Whorl profile triangular, sculpture with very coarse longitudinal ridges (Fig. 11). KORN D., A revised classification of the Carboniferous and Permian Nautilida 23 Chouteauoceratinae subfam. nov. – Whorl profile compressed oval, sculpture with numerous longitudinal ridges of the same strength (Fig. 12). Vestinautilinae subfam. nov. – Whorl profile rounded trigonal or rounded trapezoidal, sculpture with a few coarse longitudinal ridges, usually of different strength (Fig. 13). Subfamily Trigonoceratinae Hyatt, 1884 Fig. 11 Diagnosis Subfamily of the family Trigonoceratidae with cyrtoconic to evolute or subevolute conch. Whorl overlap small if present. Whorl profile ranging from triangular to depressed oval. Venter flat or rounded. Sculpture in the early species with longitudinal, equidistant ridges throughout ontogeny; advanced species with reduction of spiral ridge number. Suture line with broadly rounded lobes and saddles. Fig. 11. Subfamily Trigonoceratinae Hyatt, 1884. Trigonoceras paradoxicum (Sowerby, 1823), from de Koninck (1880). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 24 Included genera Trigonoceras M‘Coy, 1844 (Tournaisian to Viséan; 3 species). Discites M‘Coy, 1844 [non Schlotheim, 1813, nec De Haan, 1825; synonym of Discitoceras]. Nautiloceras d’Orbigny, 1849 (Tournaisian; 1 species). Triboloceras Hyatt, 1884 (Tournaisian to Viséan; 11 species). Discitoceras Hyatt, 1884 (Tournaisian; 4 species). Rineceras Hyatt, 1893 (Tournaisian to Viséan; 17 species). Rhineceras Hyatt, 1900 [synonym of Rineceras]. Apogonoceras Ruzhencev & Shimansky, 1954 (Artinskian; 1 species)? Pararineceras Turner, 1954 [synonym of Rineceras]. Stroborineceras Korn & Bockwinkel, 2022 (Tournaisian to Viséan; 4 species). Remarks The cardinal character of the representatives of the subfamily Trigonoceratidae seems to be the slightly depressed oval whorl profile in the early ontogenetic stage and the approximately equidistantly arranged spiral ridges, which are equally developed on the venter as well as on the flanks and dorsum. The general conch shape is very variable, ranging from cyrtoconic (Trigonoceras) to gyroconic (Triboloceras) and advolute (some species of Triboloceras and Rineceras) to evolute (most species of Rineceras). Almost all species have a more or less triangular or trapezoidal whorl profile. Subfamily Chouteauoceratinae subfam. nov. urn:lsid:zoobank.org:act:F1BF14B1-72AD-460F-B4F5-5632817F4C03 Fig. 12 Type genus Chouteauoceras Miller & Garner, 1953 Diagnosis Subfamily of the family Trigonoceratidae with cyrtoconic or gyroconic conch. Whorl profile compressed oval; venter rounded. Sculpture in the early species with longitudinal, equidistant ridges throughout ontogeny; advanced species with a reduction of spiral ridges. Suture line with broadly rounded lobes and saddles. Fig. 12. Subfamily Chouteauoceratinae subfam. nov. Chouteauoceras americanum (Miller & Furnish, 1939), from Miller & Furnish (1939) and Miller & Garner (1953). Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 25 Etymology The subfamily name refers to the type genus. Included genera Chouteauoceras Miller & Garner, 1953 (Tournaisian; 3 species). Ungeroceras Sturgeon & Miller, 1948 (Moscovian; 1 species). Parachouteauoceras Niko & Ozawa, 1997 (Gzhelian or Asselian; 1 species). Remarks The subfamily Chouteauoceratinae subfam. nov. contains genera that are not very well known. It is therefore uncertain whether the other two genera, in addition to the typical genus Chouteauoceras, are members of this subfamily. This is particularly true for the enigmatic Late Carboniferous genus Ungeroceras, newly described by Sturgeon & Miller (1948). This genus was synonymised by Murphy (1966) with the orthoconic genus Kionoceras Hyatt, 1884. Sturgeon et al. (1997: 57) discussed the genus, concluding that it is probably a coiled nautiloid, possibly related to the stratigraphically older Tournaisian genus Chouteauoceras (Miller & Garner 1953). Loose coiling and a compressed whorl profile are accepted as the most important criteria (Fig. 12). However, further research and new material may substantiate this hypothesis. Subfamily Vestinautilinae subfam. nov. urn:lsid:zoobank.org:act:10F74235-B3AF-4D2A-A0B8-92DBA57676A4 Fig. 13 Type genus Vestinautilus Ryckholt, 1852. Diagnosis Subfamily of the family Trigonoceratidae with discoidal to pachyconic, subevolute conch. Whorl overlap small. Whorl profile usually rounded triangular or rounded trapezoidal. Venter broadly rounded, flattened or weakly concave. Ornament with longitudinal ridges in most species; younger species show a reduction of the spiral ridges. Suture line with rounded external and lateral lobes, internal lobe shallow. Fig. 13. Subfamily Vestinautilinae subfam. nov. Vestinautilus koninckii (d’Orbigny, 1847), from de Koninck (1878). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 32 Mojsisovics, 1902 to the Jurassic genus Cenoceras Hyatt, 1884. According to the current state of knowledge, two further suborders can be derived from the Domatoceratina subordo nov. Superfamily Subclymenioidea Shimansky, 1962 Diagnosis Superfamily of the suborder Domatoceratina subordo nov. with discoidal, subinvolute to evolute conch. Whorl profile often subquadrate to polygonal, usually with distinct ventrolateral shoulder and distinct umbilical margin. Derived species show a variation of modifications including a concave or acute venter or an angular or skid-like ventrolateral shoulder. Whorl overlap extremely small to moderate. Sculpture in most species lacking. Septa simply domed but with ventral inflexion in derived species. Suture line usually depending on the whorl profile, with shallow to deep external lobe. Included families Apheleceratidae Hyatt, 1893 [nomen nullum]. Subclymeniidae Shimansky, 1962 (Early to Late Carboniferous; 6 genera, 59 species). Phacoceratidae Shimansky, 1962 (Early to Late Carboniferous; 6 genera, 13 species). Aphelaeceratidae Shimansky, 1962 [synonym of Subclymeniidae]. Epistroboceratidae fam. nov. (Early to Late Carboniferous; 4 genera, 36 species). Remarks The superfamily Subclymenioidea shows a wide range of conch morphologies and sculptures and is therefore difficult to define on the basis of adult morphology. The reason for this is a rapid morphological evolution during the Late Tournaisian and Early Viséan, which produced a high diversity of conch shapes and sculptures known from only a few other clades of nautilids. The common feature of all species is the shape of the whorl profile in the juvenile stage, characterised by sharp longitudinal ridges on a raised umbilical margin. Three evolutionary lineages can be assumed to form the superfamily Subclymenioidea: Epistroboceratidae fam. nov. – Forms that retained the polygonal shaped whorl profile once acquired; the whorl profile became more and more compressed during evolution. Whorl profile variable, usually polygonal, sculpture with few very coarse longitudinal ridges of different strength (Fig. 15). Subclymeniidae Shimansky, 1962. – Forms that developed a flattened or more or less deeply concave venter. Suture line with rather deep external lobe that was caused by a septal inflexion (Fig. 16). Phacoceratidae Shimansky, 1962. – Forms that developed an extremely compressed whorl profile with a sharp venter (Fig. 17). Family Epistroboceratidae fam. nov. urn:lsid:zoobank.org:act:88B59168-C65F-4FA4-832A-4E10A6FD9BF9 Fig. 15 Type genus Epistroboceras Turner, 1954. Diagnosis Family of the superfamily Subclymenioidea with usually subevolute conch. Whorl overlap very small. Whorl profile ranging from moderately depressed to moderately compressed, usually with polygonal KORN D., A revised classification of the Carboniferous and Permian Nautilida 33 shape. Venter usually flat. Sculpture with coarse longitudinal ridges and grooves. Suture line with broadly rounded lobes and saddles, strongly dependent on the shape of the whorl profile. Etymology The subfamily name refers to the type genus. Included genera Stroboceras Hyatt, 1884 (Tournaisian to Bashkirian; 15 species). Epistroboceras Turner, 1954 (Tournaisian to Serpukhovian; 18 species). Imonautilus Niko & Mapes, 2007 (Serpukhovian; 1 species). Trilobitoceras Korn & Bockwinkel, 2022 (Tournaisian; 2 species). Remarks The genera Stroboceras and Epistroboceras have been placed in different families or subfamilies by various authors. Miller & Garner (1953) placed Stroboceras in the family Rineceratidae; they derived Stroboceras from Discitoceras: “Discitoceras most probably also gave rise to Stroboceras by certain of its longitudinal ridges becoming very large at the expense of others. Stroboceras…” (Miller & Garner 1953: 116). Turner (1954) revised Stroboceras and proposed the new genus Epistroboceras; he placed both in the family Triboloceratidae. Shimansky (1962) placed Stroboceras and Epistroboceras in the subfamily Thrincoceratidae and later changed his mind (Shimansky 1967: 134) to assign both genera in the Trigonoceratinae. Earlier, Kummel (1964) had already included both genera in the Trigonoceratidae, without distinguishing between subfamilies. Turner (1965) included Stroboceras and Epistroboceras in the Thrincoceratinae. Dzik (1984: 173–174) had a different concept and considered the genera Stroboceras and Epistroboceras to be not closely related and placing Stroboceras in the Grypoceratidae and Epistroboceras (as a junior synonym of Aphelaeceras Hyatt, 1884) in the Phacoceratidae. Histon (1999) followed Kummel (1964) and considered Epistroboceras to be a representative of the Trigonoceratidae. Fig. 15. Representatives of the family Epistroboceratidae fam. nov., both from de Koninck (1878). A. Stroboceras sulciferum (Leveille, 1835). B. Epistroboceras bisulcatum (M’Coy, 1844). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 34 Here, the stroboceratids are distinguished as a separate family, characterised by the presence of prominent longitudinal ridges, which in many species cause a polygonal outline to the whorl profile (Fig. 15). These ridges can be seen as a transfer of the early juvenile sculpture to the adult conch. During phylogeny, these ridges have been secondarily reduced, and in the families Subclymeniidae and Phacoceratidae they are present only in the juvenile stage. Therefore, these are also included in the superfamily Grypoceratoidea. Family Subclymeniidae Shimansky, 1962 Fig. 16 Diagnosis Family of the superfamily Subclymenioidea with a discoidal, subinvolute to evolute conch; whorl overlap usually very small, coiling rate ranging from moderately high to extremely high. Whorl profile often with a distinct ventrolateral shoulder, a weakly convex, flat or concave venter and a rounded or subangular umbilical margin. Ornament in the early species with spiral lines in the juvenile and preadult stage; advanced species show the reduction of spiral lines. Siphuncle close to the venter. Suture line with a shallow to deep, broadly rounded or V-shaped external lobe that is produced by a ventral inflexion of the septum. Included genera Subclymenia d’Orbigny, 1849 (Viséan to Serpukhovian; 7 species). Aphelaeceras Hyatt, 1884 (Tournaisian to Serpukhovian; 10 species). Mesochasmoceras Foord, 1900 (Tournaisian; 1 species). Maccoyoceras Miller, Dunbar & Condra, 1933 (Tournaisian to Viséan; 11 species). Epidomatoceras Turner, 1954 (Tournaisian to Serpukhovian; 17 species). Catastroboceras Turner, 1965 (Viséan to Bashkirian; 13 species). Pseudocatastroboceras Turner, 1965 [synonym of Catastroboceras]. Fig. 16. Subfamily Subclymeniinae Shimansky, 1962. Subclymenia evoluta (Phillips, 1836), from de Koninck (1880). Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 35 Remarks Subclymenia is a remarkable genus because it has a deeply V-shaped external lobe in the suture line (Fig. 16). Unlike many nautiloids, this lobe is not caused by the geometry of the whorl profile alone, but by a ventral inflexion of the septum. Shimansky (1962) based the family Subclymeniidae on this single genus. Kummel (1964) saw Subclymenia as a genus belonging to the family Trigonoceratidae and did not accept the family Subclymeniidae. Turner (1965) downgraded the Subclymeniidae to a subfamily and expanded it to include the genera Maccoyoceras, Epidomatoceras, Catastroboceras and Pseudocatastroboceras. He showed that several species of the latter three of these genera also have a slightly angular external lobe. Shimansky (1967: 156) then withdrew the family Subclymeniidae and placed Subclymenia in the subfamily Aphelaeceratinae, together with the genera Aphelaeceras, Mesochasmoceras, Catastroboceras, Epidomatoceras and Maccoyoceras. Dzik (1984: 174) did not accept the systematic independence of a family Subclymeniidae and interpreted Subclymenia as a basal representative of the family Grypoceratidae. In the Osnovy, Shimansky (1962) named the subfamily Aphelaeceratinae for the genera Aphelaeceras and Mesochasmoceras in addition to the family Subclymeniidae. According to the original description by Meek & Worthen (1873: 522), the type species of Aphelaeceras has a V-shaped external lobe, indicating that it belongs to the Subclymeniidae. However, it is not clear whether the internal lobe in Aphelaeceras is caused by the shape of the whorl profile with a deeply concave venter or by a septal inflexion. Both Turner (1965) and Shimansky (1967) included Maccoyoceras in the subfamily Subclymeniinae. However, typical specimens of Maccoyoceras have a broadly rounded external lobe and an almost central siphuncle (Histon 1999); the genus is therefore included here in the Subclymeniidae with reservations. The Subclymeniidae are treated here as a family because the ventral inflexion of the septum is a very unusual feature. In addition, the position of the siphuncle rather close to the venter is a distinguishing feature from other families in the superfamily Subclymenioidea. The name Subclymeniidae is preferred to Aphelaeceratidae because Subclymenia characterises the family much better than Aphelaeceras. In addition to the shape of the septum and the presence of a ventral lobe, a second important feature of the subfamily is the presence of a usually subangular ventrolateral shoulder separating the usually flattened flanks from an equally flattened or concave venter. A third feature is the more or less distinct umbilical margin, which is not present in this form in the other subfamilies of the Trigonoceratidae. The family Subclymeniidae is not included here in the superfamily Trigonoceratoidea, because its morphological characteristics with a subangular umbilical margin suggests a transitional phylogenetic position leading to the Grypoceratoidea. The close morphological relationship favours placement in the latter superfamily. Family Phacoceratidae Shimansky, 1962 Fig. 17 Diagnosis Family of the superfamily Subclymenioidea with a usually subinvolute conch; coiling rate usually extremely high; whorl overlap small to moderate. Adult whorl profile extremely compressed with flat flanks and an acute venter. Ornament with longitudinal ridges or lines in the juvenile stage, adult conch smooth or with delicate growth lines. Position of the siphuncle between the centre of the whorl profile and the venter. Suture line without or with a very small external lobe and a broadly rounded lateral lobe. European Journal of Taxonomy 1017: 1–85 (2025) 36 Included genera Phacoceras Hyatt, 1884 (Viséan to Serpukhovian; 4 species). Leuroceras Hyatt, 1893 (Viséan; 1 species). Diorugoceras Hyatt, 1893 (Viséan to Serpukhovian; 3 species). Phaceras Teichert & Glenister, 1952 [nomen nullum]. Epiphacoceras Turner, 1966 (Viséan; 1 species). Askeatonoceras Turner, 1966 (Viséan; 1 species). Pseudostenopoceras Shimansky, 1967 (Serpukhovian to ? Moscovian; 3 species). Remarks The Phacoceratidae are one of the lesser-known families of Carboniferous nautiloids. Kummel (1964) did not accept the family and included Phacoceras and similar genera together with some Devonian genera (Centroceras Hyatt, 1884, Carlloceras Flower & Caster, 1935, Homaloceras Whiteaves, 1891, Strophiceras Hyatt, 1884) in the family Centroceratidae. Turner (1966) devoted a special article to the Phacoceratidae and, in discussing their phylogeny, pointed out that some of the genera were monospecific, with type species known from only a few specimens or even only a single specimen. He also saw a close relationship between Phacoceras and the Devonian centroceratids and postulated an evolutionary lineage from Carlloceras (possibly Late Devonian) through Diorugoceras to Phacoceras. This scenario is mainly based on the idea that the inverted trapezoidal whorl profile of Carlloceras transformed into an oxyconic profile during evolution. Another hypothesis was proposed by Dzik (1984: 167). He derived the Phacoceratidae, to which he also included the genera Aphelaeceras and Stenopoceras, from the stroboceratids. This phylogenetic hypothesis is quite plausible, because the morphology of the inner whorl of Phacoceras shows a morphology known from Catastroboceras, with the pronounced umbilical margin decorated by Fig. 17. Family Phacoceratidae Shimansky, 1962. Phacoceras oxystomum (Phillips, 1836), from Foord (1900). Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 37 longitudinal ridges, the flattened flanks and the distinct ventrolateral shoulder (Schmidt 1951: pl. 6 fig. 4). It is therefore not necessary to propose a long and hidden evolutionary lineage including survival through the Hangenberg Event, based on poor material. Poor preservation of type material is a problem when it comes to family composition. The two genera Epiphacoceras and Askeatomoceras newly described by Turner (1966) and Diorugoceras are based on poorly preserved material and are therefore difficult to evaluate. Superfamily Grypoceratoidea Hyatt, 1900 Diagnosis Superfamily of the suborder Domatoceratina subordo nov. with a discoidal, subinvolute to evolute conch. Whorl profile usually inverted trapezoidal with a distinct ventrolateral shoulder and a distinct umbilical margin. Derived species show a variation of modifications including a concave venter, a skidlike ventrolateral shoulder and an angular umbilical margin. Whorl overlap extremely small to moderate. Sculpture in most species lacking, in some species with short lateral ribs or ventrolateral nodes. Septa simply domed; suture line strongly dependent on the whorl profile, usually with broadly rounded lobes and narrowly rounded or subangular saddles. Included families Grypoceratidae Hyatt, 1900 (Early to Late Triassic). Domatoceratidae Miller & Youngquist, 1949 (Early Carboniferous to Late Permian; 15 genera, 73 species). Stenopoceratidae fam. nov. (Early to Middle Permian; 3 genera, 11 species). New family to be described by Korn & Hairapetian (in press) (Late Permian; 4 genera, 7 species). Remarks Grypoceras Hyatt, 1883, Domatoceras and related genera are characterised by more or less flattened flanks, which are bordered by distinct margins against the venter and the umbilical wall (Fig. 18). Usually, the ventrolateral shoulder is more strongly pronounced than the umbilical margin, being subangular, angular or even raised to form skid-like extensions. A whorl profile with both a pronounced umbilical margin and also a pronounced ventrolateral shoulder is already present in the juvenile conch, i.e., at the end of the first whorl. In this respect, Domatoceras and related genera are similar to the metacoceratids. It is worth considering whether these two groups are closely related. Three Carboniferous and Permian families, which represent evolutionary lineages, can be assigned to the superfamily Grypoceratoidea: Domatoceratidae Miller & Youngquist, 1949. – Forms that retained usually inverted trapezoidal whorl profile throughout their evolutionary history (Fig. 19). Stenopoceratidae fam. nov. – Forms that developed a very narrow venter in their evolutionary history (Fig. 20). New family to be described by Korn & Hairapetian (in press). – Forms that developed a concave venter, partly separated from a skid-like ventrolateral shoulder, in their evolutionary history (Fig. 21). European Journal of Taxonomy 1017: 1–85 (2025) 38 Family Domatoceratidae Miller & Youngquist, 1949 Figs 18A–B–19 Diagnosis Family of the superfamily Grypoceratoidea with a thinly to thickly discoidal, subinvolute to evolute conch. Whorl profile in the adult stage usually compressed subquadrate or inverted trapezoidal. Umbilical margin distinct or sharp; ventrolateral shoulder nearly rectangular to broadly rounded, rarely skid-like. Ornament consisting of fine growth lines; some species have tubercles on the ventrolateral shoulder. Suture line always with rounded but distinct external, lateral and internal lobes separated by a narrowly rounded or subacute saddles; without annular process. Included genera Pselioceras Hyatt, 1884 (Wuchiapingian to Changhsingian; 3 species). Titanoceras Hyatt, 1884 (Virgilian; 2 species). Domatoceras Hyatt, 1891 (Moscovian to Changhsingian; 38 species). Pseudometacoceras Miller, Dunbar & Condra, 1933 [synonym of Domatoceras Hyatt, 1891]. Paradomatoceras Delépine, 1937 (Bashkirian; 1 species). Plummeroceras Kummel, 1953 (Artinskian; 1 species). Neodomatoceras Ruzhencev & Shimansky, 1954 (Artinskian; 2 species). Fig. 18. Representatives of the superfamily Grypoceratoidea Hyatt, 1900. A. Family Domatoceratidae Miller & Youngquist, 1949. Penascoceras northropi (Miller & Unklesbay, 1942), from Miller & Unklesbay (1942). B. Family Domatoceratidae Miler & Youngquist, 1949. Titanoceras ponderosum (Meek, 1872), from Miller & Youngquist (1949). C. Family Stenopoceratidae fam. nov. Stenopoceras cooperi Miller & Unklesbay, 1942, from Miller & Unklesbay (1942). Scale bar units = 10 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 39 Parapenascoceras Ruzhencev & Shimansky, 1954 (Kasimovian to Roadian; 7 species). Penascoceras Ruzhencev & Shimansky, 1954 (Kungurian to Roadian; 3 species). Permodomatoceras Ruzhencev & Shimansky, 1954 (Artinskian to Wuchiapingian; 6 species). Stenodomatoceras Ruzhencev & Shimansky, 1954 (Kasimovian; 4 species). Virgaloceras Schindewolf, 1954 (Changhsingian; 1 species). Neostenopoceras Zhao, Liang & Zheng, 1978 (Changhsingian; 1 species). Shatoceras Leonova & Shchedukhin, 2020 (Asselian; 1 species). Omorphoceras Leonova & Shchedukhin, 2023 (Asselian or Sakmarian; 1 species). New genus A to be described by Korn & Ghaderi (in press) (Wuchiapingian to Changhsingian; 2 species). Remarks As with other families of Carboniferous and Permian nautilids, the justification and content of the family Domatoceratidae has been the subject of much debate; the views of the various authors were differing widely. When first described, Miller & Youngquist (1949) placed the five genera Domatoceras, Pselioceras, Stearoceras Hyatt, 1893, Stenopoceras and Titanoceras in the family Domatoceratidae. Kummel (1953) did not accept the family and synonymised it with the family Grypoceratidae. Moreover, he even considered Domatoceras to be a subgenus of Grypoceras. The genera and subgenera included by him in the Grypoceratidae were Grypoceras (Grypoceras), Grypoceras (Domatoceras), Grypoceras (Plummeroceras), Gryponautilus Mojsisovics, 1902, Stenopoceras, Menuthionautilus Collignon, 1933, Stearoceras, Titanoceras and Pselioceras. Fig. 19. Family Domatoceratidae Miller & Youngquist, 1949. Domatoceras umbilicatum Hyatt, 1891, from Hyatt (1891). Scale bar units = 10 mm. European Journal of Taxonomy 1017: 1–85 (2025) 40 Ruzhencev & Shimansky (1954) discussed the taxa belonging to this group in detail and included the four already known genera Domatoceras, Titanoceras, Pselioceras and Stenopoceras as well as the six newly named genera Penascoceras, Parapenascoceras, Permodomatoceras, Neodomatoceras, Stenodomatoceras and Parastenopoceras Ruzhencev & Shimansky, 1954. In the Osnovy (Shimansky 1962), the group was listed only as a subfamily within the family Grypoceratidae. In addition to the ten genera already mentioned, Paradomatoceras, Plummeroceras (as a subgenus of Domatoceras), Virgaloceras and Menuthionautilus were also included, the latter being the only Triassic genus. In the Treatise, Kummel (1964) reiterated his previously published view and did not accept the Domatoceratidae as a valid family. He considered the genera Stenodomatoceras, Penascoceras and Permodomatoceras newly named by Ruzhencev & Shimansky (1954) to be synonyms of Domatoceras and Parapenascoceras and Neodomatoceras as synonyms of Stearoceras. He included the genus Epidomatoceras in the family Grypoceratidae. Sobolev (1989) did not accept the independence of a family Domatoceratidae either and included the corresponding genera in the family Grypoceratidae. However, he accepted the validity of the Permian genera named by Ruzhencev & Shimansky (1954) but did not include Epidomatoceras in the family. As in other Carboniferous–Permian nautilid families, the possible phylogenetic and systematic relationships in the Domatoceratidae (or Grypoceratidae) have been intensively discussed. Ruzhencev & Shimansky (1954) followed the concept that the systematics should be based on phylogeny; they therefore divided the family into a number of genera according to hypothetical evolutionary lineages. This contrasted sharply with other approaches, such as that of Kummel (1953: 45), who had stated: “As an evolutionary unit this family appears to be closely integrated. The extensive variations experimented with in this family keep an over-all unity in both the shape of the conch and sutural development.” As a consequence, Kummel (1964) distinguished considerably fewer independent genera than Ruzhencev & Shimansky (1954) and Shimansky (1962). A reconstruction of the phylogeny was undertaken by Dzik (1984). He derived the species of the family Domatoceratidae (which he included in the Grypoceratidae) from the Early Carboniferous genus Epidomatoceras and subdivided it into several long-ranging evolutionary lineages extending from the Carboniferous to the Triassic. Contrary to earlier concepts (Shimansky 1957; Kummel 1964), he placed Germanonautilus in the evolutionary lineage of Titanoceras and the Syringonautilidae Mojsisovics, 1902 in the lineage of Domatoceras. According to this reconstruction, Stenopoceras is separated from the Grypoceratidae and is considered a descendant of Phacoceras in the family Phacoceratidae. An unanswered question is still whether certain morphological variations within the family Domatoceratidae occurred only once or iteratively. These characters include (1) the formation of a concave venter, (2) the formation of an angular ventrolateral margin and ventrolateral skids, (3) the formation of an angular umbilical margin, (4) the narrowing (but also widening) of the umbilicus, (5) the change to more compressed or depressed whorl profiles and (6) the development of ventrolateral tubercles. For example, it is not clear whether the separation of the genera Stenodomatoceras and Permodomatoceras from Domatoceras, which was justified by the reduction in umbilical width and whorl height, respectively, actually occurred only once. Therefore, it is not possible to say with certainty whether these genera are monophyletic units. KORN D., A revised classification of the Carboniferous and Permian Nautilida 41 Family Stenopoceratidae fam. nov. urn:lsid:zoobank.org:act:B054DF35-5864-4B11-A32D-33C1E7ACC7BE Figs 18C, 20 Type genus Stenopoceras Hyatt, 1893. Diagnosis Family of the superfamily Grypoceratoidea with an extremely discoidal to thinly discoidal, involute conch. Whorl profile in the adult stage compressed with very narrow venter. Ornament consisting of fine growth lines. Suture line always with rounded and small external lobe and broadly rounded lateral lobe separated by a subacute saddle, without annular process. Etymology The family name refers to the type genus. Fig. 20. Family Stenopoceratidae fam. nov. Stenopoceras abundum Miller & Thomas, 1936, from Miller & Youngquist (1949). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 48 Superfamily Pleuronautiloidea Hyatt, 1900 Diagnosis Superfamily of the suborder Tainoceratina with a discoidal, subinvolute to subevolute conch. Whorl profile in early species subquadrate with distinct ventrolateral shoulder and distinct umbilical margin. Derived species show a variation of modifications including trapezoidal, inverted trapezoidal or hexagonal whorl profiles with a less angular ventrolateral shoulder and umbilical margin. Whorl overlap is always very small. Sculpture in early species with transverse ribs and ventrolateral nodes, in derived species often with ribs and several rows of nodes. Septa simply domed, in derived species with a dorsal inflexion that produces an annular process. Suture line with broadly rounded lateral lobe and shallow lobe or low saddle on the venter. Included families Pleuronautilidae Hyatt, 1900 (Middle Permian to Late Triassic; 1 Permian genus, 10 Permian species). Gzheloceratidae Ruzhencev & Shimansky, 1954 (Early Carboniferous to Early Permian; 5 genera, 37 species). Mosquoceratidae Ruzhencev & Shimansky, 1954 (Late Carboniferous to Early Permian; 3 genera, 11 species). Aktubonautilidae Ruzhencev & Shimansky, 1954 (Early Permian; 2 genera, 2 species). Rhiphaeoceratidae Ruzhencev & Shimansky, 1954 (Early to Late Permian; 6 genera, 15 species). Metacoceratidae fam. nov. (Late Carboniferous to Late Permian; 12 genera, 101 species). Foordiceratidae fam. nov. (Middle to Late Permian; 3 genera, 14 species). Remarks Based on the phylogenetic reconstruction that was proposed by Dzik (1984), six families within the superfamily Pleuronautiloidea are distinguished here and briefly characterised as follows: Metacoceratidae fam. nov. – Ancestral taxa with a commonly subquadrate or weakly depressed whorl profile; sculpture with conical ventrolateral nodes and sometimes with dorsolateral nodes and ribs on the flank (Fig. 24). Gzheloceratidae Ruzhencev & Shimansky, 1954. – Ancestral taxa with a small conch and an elliptical or reniform whorl profile; sculpture with short ribs or transversely elongated tubercles in the middle of the flank (Fig. 25A). Aktubonautilidae Ruzhencev & Shimansky, 1954. – Taxa with a semicircular or reniform whorl profile and a broadly rounded venter; sculpture with elongate nodes on the flank (Fig. 25B). Mosquoceratidae Ruzhencev & Shimansky, 1954. – Taxa with a trapezoidal whorl profile and a convex venter; sculpture with longitudinally elongated tubercles on the outer flank (Fig. 26). Rhiphaeoceratidae Ruzhencev & Shimansky, 1954. – Taxa with an oval, reniform or trapezoidal whorl profile and a flattened venter; sculpture with short ribs on the flank (Fig. 27). Foordiceratidae fam. nov. – Derived taxa with a trapezoidal whorl profile and a flattened venter; sculpture with coarse ribs or coarse conical nodes on the outer flank (Fig. 28). Pleuronautilidae Hyatt, 1900. – Derived taxa with parallel or convergent flanks and rounded ventrolateral shoulder; sculpture with coarse ribs and sometimes with multiple rows of nodes (Fig. 29). The absence of the midventral groove separates the Pleuronautiloidea from the Tainoceratoidea. In addition, the species of the Pleuronautiloidea usually have a rectangular, trapezoidal or inverted trapezoidal whorl profile, whereas the Tainoceratoidea have a polygonal whorl profile. The sculpture of the Pleuronautiloidea does not have the characteristic rows of nodes typical for the Tainoceratoidea. KORN D., A revised classification of the Carboniferous and Permian Nautilida 49 Family Metacoceratidae fam. nov. urn:lsid:zoobank.org:act:0391FE98-A7EB-4C7A-9EDF-331C197C3EF4 Fig. 24 Type genus Metacoceras Hyatt, 1883. Diagnosis Family of the superfamily Pleuronautiloidea with an equidimensional or more commonly weakly depressed, trapezoidal to inverted trapezoidal whorl profile. Venter usually flattened, but ranging from slightly convex to slightly concave. Ventrolateral shoulder often prominent, ranging from broadly rounded to subangular. Flanks weakly convergent, parallel or weakly divergent, usually flattened and ranging from weakly convex to weakly concave. Umbilical margin usually pronounced, usually Fig. 24. Family Metacoceratidae fam. nov. A. Pseudofoordiceras cooperi (Miller, 1945), from Miller (1945). B. Pseudofoordiceras gregarium (Miller, 1945), from Miller & Youngquist (1949). C. Pseudotemnocheilus artiense (Kruglov, 1928), from Ruzhencev & Shimansky (1954). D. Metacoceras cornutum Girty, 1911, from Girty (1915). E. Metacoceras perelegans Girty, 1911, from Girty (1915). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 50 subangular in the intermediate growth stage. Sculpture with ventrolateral conical nodes, often with dorsolateral nodes and low ribs on the flank. Suture line with shallow lobes and low saddles. Internal lobe very shallow, without annular process. Etymology The family name refers to the type genus. Included genera Metacoceras Hyatt, 1883 (Moscovian to Roadian; 45 species). ? Shansinautilus Yabe & Mabuti, 1935 (Roadian; 1 species). Cooperoceras Miller, 1945 (Kungurian; 1 species). Epimetacoceras Librovitch, 1946 (Carboniferous) (nomen nudum). Pseudofoordiceras Ruzhencev & Shimansky, 1954 (Artinskian to Kungurian; 7 species). Pseudotemnocheilus Ruzhencev & Shimansky, 1954 (Artinskian to ? Changhsingian; 11 species). Tanchiashanites Zhao, 1954 (Roadian; 1 species). Mahoningoceras Murphy, 1974 (Moscovian; 3 species). Lichuanoceras Xu, 1977 (Wuchiapingian; 1 species). Sinotitanoceras Pan, 1983 (Kungurian; 1 species). Anthodiscoceras Qin, 1986 (Wuchiapingian; 1 species)? New genus C to be described by Korn & Ghaderi (in press) (Wuchiapingian to Changhsingian; 22 species). Mojsvaroceras Hyatt, 1883 (Triassic). Huanghoceras Yin, 1933 (Asselian to Wuchiapingian; 8 species). Remarks Miller et al. (1933: 166) placed six Pennsylvanian genera from the American Midcontinent in the family Tainoceratidae, namely Tainoceras, Temnocheilus, Metacoceras, Endolobus, Titanoceras and Coelogasteroceras Hyatt, 1893. This list contains a very heterogeneous collection of genera, but the authors were aware of a serious problem: “The classification of the nautiloid cephalopods is not in a satisfactory condition as is that of most of the other major groups of fossil invertebrates.” (Miller et al. 1933: 38). They discussed an earlier idea expressed by Girty (1915) to subdivide the genus Metacoceras into subgenera or genera, but concluded that “… such subdivision, however justifiable it may be from a phylogenic point of view, is so difficult, if not impossible to carry through in practice, that it would lead to endless confusion.” Consequently, they listed about 25 Carboniferous taxa at the species level. Miller & Youngquist (1949: 105) discussed the genus Metacoceras including the Permian material and repeated the problems posed by the wide range of variation in conch shape and ornament: “Normally, we would be inclined to regard many of the forms under consideration as varieties of established species, but such a procedure does not seem to be practicable in this case because of the extreme amount of variation in all of the characters involved. Therefore, more or less as a matter of expediency, we are recognizing most of the variants as distinct species.” Miller & Youngquist (1949) restricted Metacoceras to those species with conical nodes only on the outer flank or the ventrolateral shoulder; species with ventrolateral nodes extending as ribs onto the flank were assigned to Foordiceras. Because of this interpretation, they stated that many of the species formerly referred to Metacoceras should be better placed in Foordiceras. Kummel (1953: 19) proposed a different concept for the genus Metacoceras and understood it with a much wider morphological range. He separated the two subgenera M. (Metacoceras) and M. (Mojsvaroceras), the former with nearly 50 species occurring in the Carboniferous and Permian and the latter with 17 species in the Triassic. Kummel did not accept the placement of species with umbilical nodes in Foordiceras as done by Miller & Youngquist (1949), instead he stated: “The basic pattern of ornamentation of Metacoceras is that of ventrolateral and umbilical nodes.” However, at the same KORN D., A revised classification of the Carboniferous and Permian Nautilida 51 time he stated: “The species can be separated into two groups, the first including those that have only ventrolateral nodes, and the second those that have both ventrolateral and umbilical nodes.” Contrary to Miller & Youngquist (1949), Kummel (1953) saw close relationships between the genera Metacoceras and Pleuronautilus and transferred a number of Permian species that were previously assigned to Metacoceras to Pleuronautilus, although they show close affinities to Metacoceras. This reduced the number of species of Metacoceras but made Pleuronautilus a very large genus, spanning the Early Permian to the Late Triassic. Kummel estimated that there may be 58 species in the subgenus Pleuronautilus (Pleuronautilus), 24 of which are from the Permian. It is worth noting that Kummel argued that many Permian tainoceratid species previously assigned to Metacoceras or Foordiceras should be placed in Pleuronautilus based on the presence of radial ribs: “Many of these species appear to be transitional between Metacoceras and the Triassic Pleuronautilus and should be placed in the latter genus.” (Kummel 1953: 34). He listed the species, including “Nautilus dorso armatus” from Dzhulfa, under Pleuronautilus (Pleuronautilus). Ruzhencev & Shimansky (1954) proposed an alternative approach, which was very different from those previously outlined; their approach was based on proposed phylogenetic relationships that should be expressed in the classification of Metacoceras and its relatives. These authors had excellently preserved material for study and were therefore able to include the size, shape and ornamentation of early juvenile conch in their phylogenetic analysis. Ruzhencev & Shimansky (1954: 45) postulated that there are two separate evolutionary lineages within Metacoceras; the European species (including those from the South Urals) are characterised by a single row of tubercles on the ventrolateral shoulder, whereas the American species possess one row of tubercles on the ventrolateral shoulder and another on the umbilical margin. They reduced the extend of the genus Metacoceras by separating the North American Permian species with ribs on the flank as Pseudofoordiceras. Furthermore, they accepted the Asian genera Huanghoceras and Shansinautilus. In the Treatise of Invertebrate Paleontology, Kummel (1964) expressed a much more restrictive view on the tainoceratids. He did not accept the families Gzheloceratidae and Mosquoceratidae that were previously established by Ruzhencev & Shimansky (1954) and included them in the Tainoceratidae. Furthermore, ignoring the family Mosquoceratidae, he synonymised Mosquoceras Ruzhencev & Shimansky, 1954 with Metacoceras and Articheilus and placed Leonardocheilus Ruzhencev & Shimansky, 1954 in synonymy with Temnocheilus. He also synonymised a number of other genera such as Huanghoceras and Shansinautilus. In summary, Kummel’s attempt suggested the existence of some long-ranging and geographically widespread genera (Metacoceras, Pleuronautilus) with a very large number of species. Shimansky (1965), when describing the Late Permian nautiloids from Dzhulfa, noted the transitional morphology of “Metacoceras dorsoarmatum” and “M. dorashamense” with “Pleuronautilus dzhulfensis”. It seems that Shimansky avoided to name a clear character to separate the two genera. Metacoceras remained a species-rich genus. Shimansky (1967) listed 34 species, about half of which were from the Late Carboniferous and half from the Permian. He also listed 19 Permian species of Pleuronautilus, including some that had been assigned to the genera Huanghoceras and Pseudofoordiceras in an earlier paper (Ruzhencev & Shimansky 1954). These two genera as well as Shansinautilus Yabe & Mabuti, 1935 and Tungkuanoceras Hajasaka, 1947 were synonymised with Pleuronautilus. Teichert & Kummel (1973), when describing the nautiloids from the Iranian side of the Aras Valley, accepted the separation of Metacoceras (with “Metacoceras dorsoarmatum” and “M. dorashamense”) and Pleuronautilus (with “Pleuronautilus sp. indet. 1”) as previously outlined in a similar way by Shimansky (1965). Like Shimansky, they did not provide a clear reason for this choice of separation. European Journal of Taxonomy 1017: 1–85 (2025) 52 Sturgeon et al. (1997: 31) discussed in detail the morphological spectrum of Metacoceras and its relationships with other tainoceratid genera. They included Late Carboniferous species with lateral ribs and umbilical nodes in Metacoceras. An alternative division of families within the superfamily Pleuronautiloidea is proposed here. The family Metacoceratidae includes all genera that have a trapezoidal to inverted trapezoidal whorl profile and whose sculpture consists largely of ventrolateral nodes. The family Metacoceratidae is distinguished from the other families of the superfamily Pleuronautiloidea by the following criteria: The main difference with the partly rather similar species of the Pleuronautilidae is the sculpture, which in the Pleuronautilidae consists mainly of sharp ribs on the flanks, whereas in the Metacoceratidae it consists mainly of conical nodes and a few low and mostly rounded ribs. The families Mosquoceratidae and Aktubonautilidae differ from the Metacoceratidae in the very large juvenile whorl; the families Gzheloceratidae and Rhiphaeoceratidae differ from the Metacoceratidae in the more elliptical whorl cross section and, at least partly, in the presence of coarse transverse ribs. The family Foordiceratidae is easily distinguished from the Metacoceratidae by the highly divergent flanks and the absence of an umbilical margin. Family Gzheloceratidae Ruzhencev & Shimansky, 1954 Fig. 25A Diagnosis Family of the superfamily Pleuronautiloidea with a rather small conch and a weakly depressed, elliptical or reniform whorl profile. Venter flattened or slightly convex; ventrolateral shoulder, flanks and umbilical margin usually broadly rounded. Sculpture with short ribs or transversely elongated nodes on the flank. Suture line with shallow lobes and low saddles. Internal lobe very shallow, without annular process (after Ruzhencev & Shimansky 1954). Included genera Parametacoceras Miller & Owen, 1934 (Bashkirian to Moscovian; 7 species). Fig. 25. Families Gzheloceratidae Ruzhencev & Shimansky, 1954 and Aktubonautilidae Ruzhencev & Shimansky, 1954; both from Ruzhencev & Shimansky (1954). A. Gzheloceras ellipsoidale Ruzhencev & Shimansky, 1954. B. Aktubonautilus cruciformis Ruzhencev & Shimansky, 1954. Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 53 Gzheloceras Ruzhencev & Shimansky, 1954 (Gzhelian to Artinskian; 14 species). Heurekoceras Ruzhencev & Shimansky, 1954 (Artinskian; 1 species). Celox Shimansky, 1967 (Viséan to Bashkirian; 3 species). Pseudogzheloceras Dernov, 2021 (Bashkirian to Kasimovian; 12 species). Remarks The evolutionary history of the family Gzheloceratidae seems to have extended from the Viséan of the Early Carboniferous to the Early Permian, if not longer. During this long period, only few morphological changes occurred, both in the shape of the conch and in the sculpture. The species of the family show a very conservative shape of the whorl profile, which is either depressed elliptical or reniform. There is neither an angular umbilical margin nor a prominent ventrolateral shoulder developed. The sculpture consists of simple ribs or nodes on the flank (Ruzhencev & Shimansky 1954). The shape of the juvenile conch is similar to that of all other members of the superfamily Pleuronautiloidea, with the exception of the family Mosquoceratidae, which have a much larger and stouter initial conch. With an elliptical or strongly rounded trapezoidal whorl profile, the adult conch of the Mosquoceratidae has a different shape to the juvenile. Another difference from the other families is the almost straight suture line in the Gzheloceratidae. Family Aktubonautilidae Ruzhencev & Shimansky, 1954 Fig. 25B Diagnosis Family of the superfamily Pleuronautiloidea with a large, stout first whorl. Whorl profile weakly depressed, semicircular or reniform. Venter, flanks and umbilical margin broadly rounded. Sculpture with lateral, transversely elongated nodes. Suture line with a shallow external, a very shallow lateral and a rather deep internal lobe; without annular process (after Ruzhencev & Shimansky 1954). Included genera Aktubonautilus Ruzhencev & Shimansky, 1954 (Artinskian; 1 species). Basleonautilus Ruzhencev & Shimansky, 1954 (Roadian; 1 species). Remarks The family Aktubonautilidae is closest to the Rhiphaeoceratidae; there are similarities in the shape of the conch, the course of the suture line and partly in the sculpture. However, both families differ significantly in the morphology of the juvenile conch. The Aktubonautilidae are characterised by a stout first volution, whereas the Rhiphaeoceratidae have a slender, worm-like first volution. In this respect, the Aktubonautilidae are more similar to the Mosquoceratidae; however, this family differs greatly in the type of sculpture and suture line. The sculpture is formed by lateral transverse tubercles or ribs in the Aktubonautilidae but by longitudinal oval tubercles along the ventrolateral shoulder in Mosquoceratidae. In contrast to the Mosquoceratidae, the suture line in the Aktubonautilidae has only very shallow lateral lobes. Family Mosquoceratidae Ruzhencev & Shimansky, 1954 Fig. 26 Diagnosis Family of the superfamily Pleuronautiloidea with a large, rapidly growing first whorl. Whorl profile weakly depressed, subhexagonal to trapezoidal. Venter broad, weakly convex; ventrolateral shoulder European Journal of Taxonomy 1017: 1–85 (2025) 54 angular, flanks convex and strongly divergent; umbilical margin, if present, very weakly developed. Sculpture with ventrolateral, longitudinally elongated nodes. Suture line with a wide external, a narrower lateral and a narrow internal lobe; without annular process (after Ruzhencev & Shimansky 1954). Included genera Mosquoceras Ruzhencev & Shimansky, 1954 (Moscovian to Kungurian; 9 species). Articheilus Ruzhencev & Shimansky, 1954 (Artinskian; 1 species). Leonardocheilus Ruzhencev & Shimansky, 1954 (Kungurian; 1 species). Remarks According to Ruzhencev & Shimansky (1954: 85), the family Mosquoceratidae is closest to Tainoceratidae (which they interpret more broadly than it is currently done). The family Mosquoceratidae differs greatly from most of the other families of the Pleuronautiloidea in the morphology of the first volution, which is large, stout and rapidly growing in the Mosquoceratidae, whereas it is smaller and, above all, much slenderer in the other families. The similarity between these families is evident in both the shape of the conch and the suture lines. There are also sculptural differences. In the Mosquoceratidae, the tubercles are longitudinally elongated and coincide exactly with the ventrolateral shoulder; in the other families, the tubercles are usually rounded conical. The species of the family Aktubonautilidae also possess a large first whorl, but differ in the shape of the whorl profile, which is semicircular or reniform with broadly rounded venter. Family Rhiphaeoceratidae Ruzhencev & Shimansky, 1954 Fig. 27 Diagnosis Family of the superfamily Pleuronautiloidea with a small, slender first whorl. Whorl profile weakly depressed, elliptical or trapezoidal. Venter broad and weakly convex, flanks convex or slightly flattened, umbilical margin broadly rounded or absent. Sculpture with short ribs on the flank. Suture line with a low external saddle, sometimes with a shallow external lobe, a very shallow lateral and a rather deep funnel-shaped internal lobe; without annular process (after Ruzhencev & Shimansky 1954). Fig. 26. Family Mosquoceratidae Ruzhencev & Shimansky, 1954, both from Ruzhencev & Shimansky (1954). A. Mosquoceras simense Ruzhencev & Shimansky, 1954. B. Articheilus luxuriosum Ruzhencev & Shimansky, 1954. Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 55 Included genera Rhiphaeoceras Ruzhencev & Shimansky, 1954 (Sakmarian to Artinskian; 2 species). Pararhiphaeoceras Ruzhencev & Shimansky, 1954 (Asselian to Wuchiapingian; 5 species). Sholakoceras Ruzhencev & Shimansky, 1954 (Asselian to Artinskian; 4 species). Rhiphaeonautilus Ruzhencev & Shimansky, 1954 (Artinskian; 1 species). Eximioceras Shchedukhin, 2022 (Asselian or Sakmarian; 1 species). New genus D to be described by Korn & Ghaderi (in press) (Wuchiapingian; 2 species). Remarks The family Rhiphaeoceratidae can be distinguished from other Permian nautiloids by their suture line with its rather deep internal lobe. The only exceptions are the representatives of the family Aktubonautilidae, but these differ in having a much larger juvenile conch. Family Foordiceratidae fam. nov. urn:lsid:zoobank.org:act:AF7DFEF1-92F2-46BC-8A62-32D89A6BDA4A Fig. 28 Type genus Foordiceras Hyatt, 1893. Diagnosis Family of the superfamily Tainoceratoidea with a trapezoidal whorl profile; ventrolateral shoulder rounded, flanks strongly divergent. Sculpture with ventrolateral conical nodes, sometimes with low ribs on the flank. Suture line with shallow lobes and low saddles. Internal lobe very shallow, without annular process. Etymology The family name refers to the type genus. Included genera Foordiceras Hyatt, 1893 (Wuchiapingian to Changhsingian; 8 species). Foordoceras Girty, 1908 [nomen nullum]. Araxonautilus Shimansky, 1979 (Wordian to Wuchiapingian; 3 species). Fig. 27. Family Rhiphaeoceratidae Ruzhencev & Shimansky, 1954, all from Ruzhencev & Shimansky (1954). A. Rhiphaeoceras venustum Ruzhencev & Shimansky, 1954. B. Pararhiphaeoceras tastubense Ruzhencev & Shimansky, 1954. C. Sholakoceras bisulcatum Ruzhencev & Shimansky, 1954. Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 56 New genus E to be described by Korn & Ghaderi (in press) (Wuchiapingian to Changhsingian; 3 species). Remarks The repeated stratigraphic occurrence of nautiloids with an open umbilicus, a trapezoidal whorl profile and a sculpture with ventrolateral ribs or nodes in the Late Carboniferous (e.g., Latitemnocheilus), Early Permian (e.g., Pseudotemnocheilus, Articheilus) and Late Permian (e.g., Foordiceras) is a phenomenon that is not easy to explain. In order to approach this problem, four hypotheses can be discussed: Hypothesis 1: the species of interest are a monophyletic unit descended from an ancestor with similar conch geometry and sculpture, such as the Early Carboniferous genus Temnocheilus. This may be the most parsimonious explanation in terms of morphological evolution, but it would imply a very long and simple evolutionary lineage starting in the Late Viséan and ending in the Changhsingian. It should be noted, however, that this hypothesis is mainly based on adult morphology; the juvenile conch, which is unknown in many species, plays only a minor role. For example, it is not clear whether the genera discussed also possess the characteristic bicarinate juvenile whorl profile, the longitudinal ornamentation and the deep and V-shaped inner lobe of Temnocheilus. Sturgeon et al. (1982: 1461; 1997: 48) proposed an origin of Latitemnocheilus from Temnocheilus, because they found the longitudinal ornament characteristic for Temnocheilus also in similar development in two species of Latitemnocheilus, but not in Metacoceras. As a consequence, they concluded that “… temnocheilids were not the ancestors of, or closely related to, Metacoceras as suggested by Miller et al. (1933: p. 160), Miller & Owen (1934, p. 221) and Miller & Youngquist (1949, p. 94)”. Hypothesis 2: the species compose a monophyletic unit, descended from a Late Carboniferous genus such as Metacoceras by a transformation of the inverted trapezoidal or almost rectangular whorl profile to a trapezoidal shape. This was accompanied by a regression of the angular umbilical margin. After Fig. 28. Family Foordiceratidae fam. nov. Foordiceras goliathum (Waagen, 1879), from Miller & Youngquist (1949), after Waagen (1879). Scale bar units = 10 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 57 this initial evolution, the lineage continued with only minor morphological changes throughout the Late Permian. An origin of Latitemnocheilus from Metacoceras may be explained by the rather close resemblance of the adult morphology of these two genera, which differ mainly in the presence or absence of a pronounced umbilical margin. Hypothesis 3: the species do not share the same phylogenetic origin; the Late Carboniferous and Permian nautiloids with trapezoidal whorl profile represent unrelated clades. In this hypothesis, the Early Permian genera such as Pseudotemnocheilus independently originated from Metacoceras or a similar genus by deflation of the umbilical margin. This scenario was proposed by Ruzhencev & Shimansky (1954: 45). Dzik (1984: 160) suggested to amalgamate the Early Permian species attributed to Metacoceras and Pseudotemnocheilus by Ruzhencev & Shimansky (1954) in one genus because of the minor morphological differences between the species. Hypothesis 4: the species repeatedly descended from ancestors with a pronounced umbilical margin in the Late Carboniferous, Early Permian and Late Permian, respectively. This may be the morphologically least parsimonious solution. At the same time, it turns out that in all three cases there are morphoclines in each of the time intervals, which can be used as a good supporting argument for this hypothesis. The ontogeny of the juvenile conch can provide solid information on the phylogenetic relationships between these species. Although the juvenile conch of the Late Permian genera is poorly known, it appears that it is more similar to the Early Permian genus Pseudotemnocheilus, with its more circular whorl profile, than to the Early Carboniferous genus Temnocheilus, which has a bicarinate juvenile conch. This may argue for an evolutionary lineage connecting the Permian groups, i.e., a descent of the Foordiceratidae from the metacoceratids. Family Pleuronautilidae Hyatt, 1900 Fig. 29 Diagnosis Family of the superfamily Pleuronautiloidea with a commonly subquadrate or weakly depressed whorl profile; venter ranging from convex to weakly concave, ventrolateral shoulder and umbilical margin often pronounced, flanks usually weakly convergent. Sculpture with numerous ribs on the flank, sometimes with conical tubercles and more rarely with spiral ridges. An annular process is present in the advanced species. Included genera New genus C to be described by Korn & Hairapetian (in press) (Wordian to Changhsingian; 10 species). Pleuronautilus Mojsisovics, 1882 (Triassic). Phloioceras Hyatt, 1884 (Triassic). Anoploceras Hyatt, 1900 (Triassic). Encoiloceras Hyatt, 1900 (Triassic). Enoploceras Hyatt, 1900 (Triassic). Holconautilus Mojsisovics, 1902 (Triassic). Trachynautilus Mojsisovics, 1902 (Triassic). Sibyllonautilus Diener, 1915 (Triassic). Phaedrysmocheilus Shimansky & Erlanger, 1955 (Triassic). Arctonautilus Sobolev, 1989 (Triassic). Grumantoceras Sobolev, 1989 (Triassic). European Journal of Taxonomy 1017: 1–85 (2025) 64 illustration of the holotype. Hyatt (1894: 538) did not know the provenance or stratigraphic position of the specimen and believed it to be Devonian. This was confirmed by Charles Schuchert, who suggested the Iberg in the Harz Mountains as the locality, based on a spiriferid brachiopod attached to the nautilid. Kummel (1963: 356) had this information checked by G.A. Cooper, who concluded that it was probably a Viséan brachiopod. If the specimen indeed comes from the Iberg, which is by no means certain, it could actually be a specimen from the well-known Early Carboniferous Neptunian dykes, in which cephalopods and spiriferids have been identified (e.g., Schindewolf 1951). The conch morphology of the holotype of Potoceras dubium is very similar to the typical Early Carboniferous representatives of Liroceras or Bistrialites, such as those described by Foord (1891) and Turner (1954) from northern England, by Trenkner (1868) and Schmidt (1951) from the Harz Mountains, and by Korn & Klug (2023) from the Anti-Atlas of Morocco. For this reason, too, it is reasonable to assume that the stratigraphic age of Potoceras dubium is Early Carboniferous. Potoceras may even be a senior synonym of Bistrialites or Liroceras, but this problem cannot be solved at present because of the limited data available. Dzik (1984: 168) proposed a fundamentally different hypothesis in which the family Liroceratidae (which he defined more broadly than the other authors) was derived from an Early Carboniferous group of nautilids, that is the family Trigonoceratidae. He based this hypothesis on the juvenile ornament with spiral ridges present in both Liroceras and Vestinautilus and postulated that both genera were related through Bistrialites Turner, 1954. There are several reasons for accepting this suggestion. An evolution from Vestinautilus to Liroceras would mainly involve a narrowing of the umbilicus, although this would be mainly due to an expansion of the ventral zone (Fig. 3E, J). Therefore, the spiral ridges are still located in the area of the (topographic) ventrolateral shoulder in Vestinautilus, in the middle of the flank in Bistrialites and in the (topographic) umbilical margin in Liroceras. Phylogeny Several scenarios have been developed to clarify the phylogeny within the liroceratids. Shimansky (1957, 1962) proposed three independent evolutionary lineages, the first of which (Koninckioceratidae) is placed here in the suborder Temnocheilina. The superfamily Clydonautilaceae was derived from the Lirocerataceae by Shimansky. This phylogenetic scheme was supported by Kummel (1964). Descendants Flower & Kummel (1950) linked, albeit with a question mark, the families that are now considered part of the suborder Nautilina Agassiz, 1847 (e.g., Nautilidae de Blainville, 1825, Aturiidae Chapman, 1857) to the family Paranautilidae, which they accepted as valid. This view was not shared by later authors (Shimansky 1962; Kummel 1964; Dzik 1984). Superfamily Liroceratoidea Miller & Youngquist, 1949 Diagnosis Superfamily of the suborder Liroceratina with a pachyconic and rarely discoidal or globular, subinvolute to involute conch. Whorl profile usually circular or depressed oval without distinct ventrolateral shoulder; in some species with a pronounced but rounded ventrolateral shoulder. Dorsal whorl zone usually small to moderately deep. Juvenile sculpture in the early species with spiral lines that may be restricted to the umbilical area; derived species are often smooth. Suture line very simple, almost straight across flanks and venter. KORN D., A revised classification of the Carboniferous and Permian Nautilida 65 Included families Liroceratidae Miller & Youngquist, 1949 (Early Carboniferous to Late Permian; 17 Palaeozoic genera, 118 Palaeozoic species). Coloceratidae Hyatt, 1893 [homonym; synonym of Liroceratidae Miller & Youngquist, 1949]. Paranautilidae Kummel in Flower & Kummel, 1950 (Early to Late Triassic). Permonautilidae Barskov & Shilovsky, 2014 (Middle to Late Permian; 1 genus, 10 species). Planetoceratidae fam. nov. (Early to Late Carboniferous; 1 genus, 9 species). New family to be described by Korn & Ghaderi (in press) (Late Permian; 3 genera, 5 species). Remarks The species of the Liroceratoidea can easily be distinguished from the species of the other superfamilies of the Liroceratina by the simple septal shape and thus the very simple, almost straight suture line. The Palaeozoic families are characterised as follows: Liroceratidae Miller & Youngquist, 1949 – Ancestral forms with involute or subinvolute conch, umbilical wall usually rounded (Fig. 32). Planetoceratidae fam. nov. – Ancestral forms, in which the terminal whorl detaches from the preceding whorl (Fig. 33). Permonautilidae Barskov & Shilovsky, 2014 – Advanced forms, which possess a prominent thorn-like umbilical process in the adult stage (Fig. 34). New family to be described by Korn & Ghaderi (in press) – Ancestral forms with a pronounced umbilical margin and a flattened umbilical wall; the venter has the tendency to become flattened or weakly concave (Fig. 35). Family Liroceratidae Miller & Youngquist, 1949 Fig. 32 Diagnosis Family of the superfamily Liroceratoidea with a usually pachyconic or globular, subinvolute to subevolute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch in the early species, the venter can be flattened or concave in advanced species. Umbilical margin rounded; umbilical wall usually convex. Ornament usually consisting of fine growth lines; spiral lines occur in some genera. Septum simple in shape, concavely domed; suture line very simple, almost straight across flanks and venter or with small lobes and saddles. Included genera Solenoceras Hyatt, 1884 [homonym of Solenoceras Conrad, 1860; objective synonym of Coelogasteroceras]. Coelogasteroceras Hyatt, 1893 (Bashkirian to Changhsingian; 11 species). Coloceras Hyatt, 1893 [homonym of Coloceras Taschenberg, 1882; synonym of Liroceras]. Stearoceras Hyatt, 1893 (Serpukhovian to Changhsingian; 10 species). Peripetoceras Hyatt, 1894 (Serpukhovian to Changhsingian; 22 species). Potoceras Hyatt, 1894 (? Viséan; 1 species). Nannoceras Hyatt, 1894 [nomen nullum; synonym of Peripetoceras]. Conradiceras Cossmann, 1900 [objective synonym of Coelogasteroceras]. Cyclonautilus Hind, 1910 [synonym of Peripetoceras]. Liroceras Teichert, 1940 (Viséan to Changhsingian; 47 species). Condraoceras Miller, Lane & Unklesbay, 1947 (Kasimovian to Artinskian; 3 species). Periptoceras Chao, 1954 [nomen nullum; synonym of Peripetoceras]. Hemiliroceras Ruzhencev & Shimansky, 1954 (Bashkirian to Artinskian; 6 species). European Journal of Taxonomy 1017: 1–85 (2025) 66 Bistrialites Turner, 1954 (Viséan to Serpukhovian; 5 species). Pseudophacoceras Turner, 1966 (? Viséan; 1 species). Neobistrialites Tucker, Mapes & Aronoff, 1978 (Moscovian; 1 species). Jianoceras Ma, 1997 (Permian; 1 species). Nemdoceras Barskov & Shilovsky, 2014 (Roadian; 3 species). Paraliroceras Barskov & Shilovsky, 2014 (Roadian to Changhsingian; 2 species). Tatianautilus Barskov & Shilovsky, 2014 (Roadian; 1 species). Leniceras Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species). Shikhanonautilus Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species). Thyoceras Leonova & Shchedukhin, 2020 (Asselian or Sakmarian; 1 species). New genus G to be described by Korn & Ghaderi (in press) (Wuchiapingian; 1 species). Perunautilus Crick & Sobolev, 1994 (Triassic). Tomponautilus Sobolev, 1989 (Triassic). Remarks The Liroceratidae are probably the family with the longest stratigraphic range among the Palaeozoic Nautilida, extending from the Early Carboniferous to the Triassic. It can be regarded as a morphologically very stable clade in which morphological changes occurred only very rarely. Some of Fig. 32. Family Liroceratidae Miller & Youngquist, 1949, both from Hind (1910). A. Liroceras globosum (Hind, 1910). B. Peripetoceras umbilicatum (Hind, 1910). Scale bar units: A = 10 mm; B = 5 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 67 the new morphological developments have been separated as independent families (Permonautilidae, Paranautilidae), so that the Liroceratidae represent the conservative stem group. The distribution of species among the 18 Palaeozoic genera within the Liroceratidae shows a very asymmetric picture. Nine genera are represented by only one species, while Liroceras and Peripetoceras are very diverse with 47 and 22 species, respectively. In addition, many species are known from only one specimen. As with many other groups of Nautilida, a revision is necessary and will probably change the picture so that fewer genera and species can be accepted. Family Planetoceratidae fam. nov. urn:lsid:zoobank.org:act:F919D8AF-4002-4CFE-BD02-0E8CFFC2EE66 Fig. 33 Type genus Planetoceras Hyatt, 1893. Diagnosis Family of the superfamily Liroceratoidea with a pachyconic, usually subinvolute conch; the terminal portion of the conch is detached from the preceding whorl. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch, umbilical margin pronounced, umbilical all flat and steep. Ornament consisting of fine growth lines. Septum simple in shape, concavely domed; suture line very simple, almost straight across flanks and venter or with small lobes and saddles. Etymology The family name refers to the type genus. Fig. 33. Family Planetoceratidae fam. nov. Planetoceras globatum (Sowerby, 1824), from Foord (1900). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 68 Included genus Planetoceras Hyatt, 1893 (Tournaisian to Kasimovian; 9 species). Remarks The placement of Planetoceras was problematic. Planetoceras retardatum Hyatt, 1893 and P. globatum (Sowerby, 1824) from early Late Tournaisian limestones of Belgium and Ireland have a peculiar conch morphology with a terminal whorl, which is depressed and oval in profile, and is detached from the preceding whorl. It is not possible to conclude whether the detached final volution in Planetoceras is due to increased coiling or secondary uncoiling. Contrary to previous authors, a separate family is established for the genus Planetoceras and it is placed in the superfamily Liroceratoidea. Kummel (1964) placed Planetoceras in the then very heterogeneous family Koninckioceratidae. Shimansky (1967) also placed it together with the genera Millkoninckioceras and Lophoceras in the family Koninckioceratidae, which consisted of only three genera. The shape of the inner volutions and their sculpture argue against placement in the Koninckioceratidae. Planetoceras has a distinct umbilical margin, with some coarse longitudinal ridges, giving it a morphology that is much closer to that of early liroceratids. Another common feature with the liroceratids is the expansion of the flank and venter area. In contrast to liroceratids, the umbilical wall of Planetoceras is flattened and steep. However, the most important distinguishing feature is the detachment of the adult whorl spiral. Family Permonautilidae Barskov & Shilovsky, 2014 Fig. 34 Diagnosis Family of the superfamily Liroceratoidea with a pachyconic or globular, usually subinvolute to subevolute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch in the early forms, the venter can be flattened or concave in advanced forms. Terminal aperture with long lateral shell processes emerging from the umbilical margin. Ornament Fig. 34. Family Permonautilidae Barskov & Shilovsky, 2014. Permonautilus cornutus (Golovkinsky, 1869), from Barskov et al. (2014). Scale bar units = 5 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 69 consisting of fine or coarse growth lines. Septum simple in shape, concavely domed; suture line very simple, almost straight across flanks and venter or with small lobes and saddles. Included genera Permonautilus Kruglov, 1933 (Roadian to Wuchiapingian; 10 species). Alexandronautilus Shimansky, 1962 [synonym of Permonautilus Kruglov, 1933]. Remarks The family Permonautilidae was introduced by Barskov & Shilovsky in Barskov et al. (2014) on the basis of virtually one character to separate it from the Liroceratidae, namely the presence of long lateral shell processes emerging from the umbilical margin. Such a process is apparently absent in the other genera of the superfamily Liroceratoidea. Very similar processes are only known from the family Solenochilidae (suborder Solenochilina), which is not related to the Permonautilidae. Barskov & Shilovsky in Barskov et al. (2014: 1391) clarified that the Permonautilidae are separated from the Solenochilidae by the position of the siphuncle, which is subcentral or centrodorsal in the Permoceratidae and subventral in the Solenochilidae. The occurrence of the long shell processes in the Early to Late Carboniferous Solenochilidae and the Middle to Late Permian Permonautilidae is indeed a very interesting phenomenon, as both families belong to two unrelated evolutionary lineages that were probably separated already in the Devonian (Dzik 1984). Although the distinction between the two families Liroceratidae and Permonautilidae is based on only one character, the separation is still accepted here with reservations. New family Korn & Ghaderi (in press) Fig. 35 Diagnosis Family of the superfamily Liroceratoidea with a usually pachyconic, subinvolute to involute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter usually separated by distinct ventrolateral shoulder, venter or concave. Umbilical margin subangular or angular; umbilical wall steep, flattened. Ornament usually consisting of fine growth lines. Septum simple in shape, concavely domed; suture line with shallow lobes on venter and flank (from Korn & Ghaderi in press: 98). Included genera New genus H to be described by Korn & Ghaderi (in press) (Changhsingian; 2 species). New genus E to be described by Korn & Hairapetian (in press) (Wuchiapingian; 2 species). New genus F to be described by Korn & Hairapetian (in press) (Wuchiapingian; 1 species). Remarks The new family is characterised by a combination of characters not found in any other family of Palaeozoic nautilids. This is the combination of a rather stout conch with a very pronounced umbilical margin and also a sometimes pronounced ventrolateral shoulder. While the first character suggests a placement in the superfamily Liroceratoidea, the second and third characters show a closer morphological relationship to the superfamilies Pleuronautiloidea and Grypoceratoidea. Unfortunately, the early ontogenetic development of the conch in the species of the new family is not known. However, the material shows that the pronounced umbilical margin is present early in ontogeny and that this feature can therefore be considered apomorphic, whereas the ventrolateral shoulder does not assume a subangular shape until a late ontogenetic stage, if at all. Therefore, these genera are included here as a new family of the superfamily Liroceratoidea (from Korn & Ghaderi in press: 98). European Journal of Taxonomy 1017: 1–85 (2025) 70 Superfamily Ephippioceratoidea Miller & Youngquist, 1949 Diagnosis Superfamily of the suborder Liroceratina with a pachyconic or globular, involute to subinvolute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch. Ornament usually consisting of fine growth lines; some species have spiral lines or fine ribs. Septum strikingly bilobate; suture line with high external saddle. Included family Ephippioceratidae Miller & Youngquist, 1949 (Early Carboniferous to Early Permian; 3 genera, 26 species). Family Ephippioceratidae Miller & Youngquist, 1949 Fig. 36 Diagnosis Family of the superfamily Ephippioceratoidea with a pachyconic or globular, involute to subinvolute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch. Ornament usually consisting of fine growth lines; some species have spiral lines or fine ribs. Septum strikingly bilobate; suture line with high external saddle. Included genera Ephippioceras Hyatt, 1894 (Viséan to Roadian; 16 species). Fig. 35. New family to be described by Korn & Ghaderi (in press). New species to be described by Korn & Ghaderi (in press), lateral and apertural views, reconstruction of apertural view, from Korn & Ghaderi (in press). Scale bar units = 1 mm. KORN D., A revised classification of the Carboniferous and Permian Nautilida 71 Megaglossoceras Miller, Dunbar & Condra, 1933 (Bashkirian to Asselian; 9 species). Arthuroceras Shimansky, 1962 (Bashkirian; 1 species). Remarks The composition of the family Ephippioceratidae proposed here agrees with that outlined by Shimansky (1962) and Kummel (1964), while Dzik (1984) included the genera Ephippioceras and Megaglossoceras, together with Styrionautilus and others, in the family Liroceratidae. The members of the family Ephippioceratidae cannot be confused with other nautiloids if the shape of the septa is preserved. Ephippioceras and Megaglossoceras are characterised by a very conspicuous bilobate septal surface, the peculiar shape of which is produced by a high ventrodorsal ridge dividing the entire septum (Fig. 36). There are apparently no known species that could be considered as intermediates between Bistrialites or Liroceras and Ephippioceras. Dzik (1984: 169) discussed the origin of Ephippioceras and suggested Stearoceras as a possible ancestor. The reason for this suggestion was that the suture line of Stearoceras has a ventral undulation, which may have developed into the conspicuous external saddle. According to Dzik (1984), Ephippioceras gave rise to Megaglossoceras, which is the ancestor of the Triassic genus Styrionautilus. This assumption is based on the superficially similar sutures with a ventral saddle. However, it overlooks the fact that the ventral saddle in Ephippioceras and Megaglossoceras was produced by the bilobate deformation of the entire septum by a high ridge, which is not present in Clydonautilus Mojsisovics, 1882 and related genera. Therefore, a phylogenetic lineage from the Liroceratidae to the Clydonautilidae is preferred here. Fig. 36. Family Ephippioceratidae Miller & Youngquist, 1949. Ephippioceras ferratum (Cox, 1858), from Miller & Youngquist (1949). Scale bar units = 1 mm. European Journal of Taxonomy 1017: 1–85 (2025) 72 Suborder Solenochilina Flower, 1950 Diagnosis Suborder of the order Nautilida, in which the conch form ranges from cyrtoconic, gyroconic to nearly involute with extraordinarily high coiling rate. Dorsal whorl zone missing or very small. Shell surface usually smooth. Suture line nearly straight with a small external lobe. Siphuncle in marginal ventral position. Included superfamilies Aipoceratoidea Hyatt, 1884 (Early Carboniferous to Early Permian; 7 genera, 54 species). Scyphoceratoidea Ruzhencev & Shimansky, 1954 (Early Carboniferous to Early Permian; 9 genera, 23 species). Remarks Taxonomy The position of the solenochilids within the order Nautilida has been very unstable over the decades, with different authors expressing sometimes very different opinions. Flower & Kummel (1950) presented them as an isolated order Solenochilida, derived (with a question mark) from the family Barrandeoceratidae Foerste, 1925. Shimansky (1957) placed the superfamily Solenochilaceae, to which he included the families Litogyroceratidae Shimansky, 1957, Scyphoceratidae, Dentoceratidae and Solenochilidae, in the suborder Rutoceratina. Later, Shimansky (1962, 1967) modified this scheme only in the minor detail of giving priority to the names Aipoceratidae and Aipocerataceae over the names Solenochilidae and Solenochilaceae. Furnish & Glenister (in Kummel 1964: K440) interpreted the superfamily Aipocerataceae, to which they assigned the families Aipoceratidae, Solenochilidae and Scyphoceratidae, as an independent evolutionary lineage, which possibly derived from the superfamily Tainocerataceae (Kummel 1964: K385). Dzik (1984) considered the families Aipoceratidae and Solenochilidae to belong to an uncertain suborder. He suppressed the family Scyphoceratidae that was recognised by the other authors and placed the genera belonging to it in the orthoceratid family Cycloceratidae Hyatt, 1900 (Dzik 1984: 130). Due to the lack of new information, little can be contributed here to the two competing systematic interpretations. However, on the basis of the somewhat marginal position of the siphuncle, the family Scyphoceratidae is provisionally retained in the suborder Solenochilina. Morphology and subdivision The suborder Solenochilina is characterised by two main features, which are the ventrally located siphuncle and the very high coiling rate. Two superfamilies are recognised here: Aipoceratoidea Hyatt, 1884. – Conch cyrtoconic, gyroceraconic to subinvolute or involute, pachyconic to globular with a very mall whorl overlap zone. Scyphoceratoidea Ruzhencev & Shimansky, 1954. – Conch from nearly orthoconic to cyrtoconic. Phylogeny The origin of the suborder Solenochilina has been discussed several times in the literature and cannot yet be considered sufficiently resolved. Flower (1955: 256) interpreted all Carboniferous coiled nautiloids as derived from rutoceratids and explicitly included the solenochilids: “Probably the small Late Paleozoic order the Solenochilida has its origin also in the Rutoceratida”. This concept was supported by Shimansky KORN D., A revised classification of the Carboniferous and Permian Nautilida 73 (1957, 1962, 1967), Kummel (1964) and Flower (1964: 5). Flower (1964: 12), however, stated that the solenochilids were “almost certainly” allied to the order Oncoceratida. Dzik (1984: 156) was not sure whether the two families, Aipoceratidae and Solenochilidae, were phylogenetically related and suggested the Devonian genera Geitonoceras Zhuravleva, 1974 and Cranoceras Hyatt, 1884 as possible ancestors. According to Dzik (1984: 157), the data suggest that solenochilids “... are much more closely related to the Oncoceratidae than to the Nautilida”. But at the same time, he suggested that “... it is more reasonable to retain the Aipocerataceae in the Nautilida until their systematic position is known”. That view is shared here. Superfamily Aipoceratoidea Hyatt, 1884 Fig. 37 Diagnosis Superfamily of the suborder Solenochilina, in which the conch form ranges from gyroconic to nearly involute with extraordinarily high coiling rate. Whorl profile laterally compressed to weakly depressed. Included families Aipoceratidae Hyatt, 1884 (Early Carboniferous to Early Permian; Permian; 5 genera, 18 species). Solenochilidae Hyatt, 1893 (Early Carboniferous to Middle Permian; 2 genera, 36 species). Remarks A very apt characterisation of the superfamily Aipoceratoidea was given by Shimansky (1967: 39) (translated from Russian): “The origin of the peculiar Late Palaeozoic nautiloids, grouped in the superfamily Aipocerataceae and characterised by a smooth conch of various shapes, a ventral position of the siphuncle and an almost straight suture line, is not very clear. There seems to be no doubt about Fig. 37. Family Solenochilidae Hyatt, 1893. Solenochilus springeri (White & St. John, 1868), from Furnish & Glenister in Kummel (1964). Scale bar units = 10 mm. European Journal of Taxonomy 1017: 1–85 (2025) 80 Superfamily Pleuronautiloidea Hyatt, 1900 Family Pleuronautilidae Hyatt, 1900 Family Gzheloceratidae Ruzhencev & Shimansky, 1954 Family Mosquoceratidae Ruzhencev & Shimansky, 1954 Family Aktubonautilidae Ruzhencev & Shimansky, 1954 Family Rhiphaeoceratidae Ruzhencev & Shimansky, 1954 Family Metacoceratidae fam. nov. Family Foordiceratidae fam. nov. Suborder Liroceratina Flower, 1955 Superfamily Liroceratoidea Miller & Youngquist, 1949 Family Liroceratidae Miller & Youngquist, 1949 Family Permonautilidae Barskov & Shilovsky, 2014 Family Paranautilidae Kummel in Flower & Kummel, 1950 Family Planetoceratidae fam. nov. New family to be described by Korn & Ghaderi (in press) Superfamily Ephippioceratoidea Miller & Youngquist, 1949 Family Ephippioceratidae Miller & Youngquist, 1949 Superfamily Clydonautiloidea Hyatt, 1900 Suborder Solenochilina Flower, 1950 Superfamily Aipoceratoidea Hyatt, 1884 Family Aipoceratidae Hyatt, 1884 Family Solenochilidae Hyatt, 1893 Superfamily Scyphoceratoidea Ruzhencev & Shimansky, 1954 Family Scyphoceratidae Ruzhencev & Shimansky, 1954 Family Dentoceratidae Ruzhencev & Shimansky, 1954 Family Neptunoceratidae Shimansky, 1957 Acknowledgements I greatly acknowledge the reviews of an earlier version of the manuscript by Jerzy Dzik (Warsaw) and Andy King (Watchet, Somerset) as well as the careful editing by Kristiaan Hoedemakers and Radka Rosenbaumová. References Abich H. 1878. Geologische Forschungen in den kaukasischen Ländern. Theil I. Eine Bergkalkfauna aus der Araxesenge bei Djoulfa in Armenien. Hölder, Wien. Arkhipov Y.V. & Barskov I.S. 1970. O nautilidakh so slozhno raschlenennoy peregorodochnoy liniyey. Doklady Akademii Nauk SSSR 195: 464–466. [In Russian.] Barskov I.S., Leonova T.B. & Shilovsky O.P. 2014. Middle Permian cephalopods of the Volga-Ural Region. Paleontological Journal 48: 1331–1414. https://doi.org/10.1134/S0031030114130012 Chao K.-K. 1954. Permian cephalopods from Tanchiashan, Hunan. Acta Palaeontologica Sinica 2: 1–58. de Koninck L.G. 1844. Description des animaux fossiles qui se trouvent dans le terrain carbonifère de la Belgique. H. Dessain, Brussels. de Koninck L.G. 1878. Faune du Calcaire Carbonifère de la Belgique. Première partie. Poissons et genre Nautile. Annales du Museé royal d’Histoire naturelle de Belgique 2: 1–152. https://doi.org/10.5962/bhl.title.149304 KORN D., A revised classification of the Carboniferous and Permian Nautilida 81 de Koninck L.G. 1880. Faune du Calcaire Carbonifère de la Belgique, deuxième partie. Genres: Gyroceras, Cyrtoceras, Gomphoceras, Orthoceras, Subclymenia et Goniatites. Annales du Museé royal d’Histoire naturelle, Belgique 5: 1–333. Dernov V. 2021. Pseudogzheloceras – a new genus of Carboniferous nautilids (Cephalopoda) from Europe and North Africa. Geo&Bio 21: 87–94. https://doi.org/10.15407/gb2109 Dzik J. 1984. Phylogeny of the Nautiloidea. Palaeontologia Polonica 45: 1–219. Dzik J. & Korn D. 1992. Devonian ancestors of Nautilus. Paläontologische Zeitschrift 66: 81–98. https://doi.org/10.1007/BF02989479 Flower R.H. 1955. Saltations in nautiloid coiling. Evolution 9: 244–260. https://doi.org/10.1111/j.1558-5646.1955.tb01535.x Flower R.H. 1963. Two Permian cyrtocones from New Mexico with discussion of their relationships. Journal of Paleontology 37: 86–96. Flower R.H. 1964. The Nautiloid order Ellesmeroceratida (Cephalopoda). Memoirs of the State Bureau of Mines and Mineral Resources, New Mexico Institute of Mining and Technology 12: 1–234. https://doi.org/10.58799/M-12 Flower R.H. & Kummel B. 1950. A classification of the Nautiloidea. Journal of Paleontology 24: 604– 616. Foord A.H. 1891. Catalogue of the Fossil Cephalopoda in the British Museum, Part II. Containing the Remainder of the Suborder Nautiloidea, Consisting of the Families Lituitidae, Trochoceratidae, and Nautilidae, with a Supplement. Order of the Trustees, London. Foord A.H. 1900. Monograph on the Carboniferous Cephalopoda of Ireland. Part III. Containing the Families Tainoceratidae, Trigonoceratidae, Triboloceratidae, Rineceratidae, Coloceratidae, and Solenocheilidae (in Part). Monographs of the Palaeontographical Society 54: 49–126. https://doi.org/10.1080/02693445.1900.12035492 Furnish W.M., Glenister B.F. & Hansman R.H. 1962. Brachycycloceratidae, novum, deciduous Pennsylvanian nautiloids. Journal of Paleontology 36: 1341–1356. Girty G.H. 1915. Fauna of the Wewoka Formation of Oklahoma. Bulletin of the U.S. Geological Survey 544: 1–353. Gordon M. jr. 1965. Carboniferous Cephalopods of Arkansas. Professional Papers, U.S. Geological Survey 460: 1–322. https://doi.org/10.3133/pp460 Haniel C.A. 1915. Die Cephalopoden der Dyas von Timor. In: Wanner J. (ed.), Paläontologie von Timor nebst kleineren Beiträgen zur Paläontologie einiger anderer Inseln des ostindischen Archipels: 1–153. Schweizerbart, Stuttgart. Hind W. 1910. On four new Carboniferous nautiloids and a goniatite new to Great Britain. Proceedings of the Yorkshire Geological Society 17: 97–109. https://doi.org/10.1144/pygs.17.2.97 Histon K. 1999. A revision of A.H. Foord’s monograph of Irish Carboniferous nautiloid cephalopods (1897–1901). Part 2. Monographs of the Palaeontographical Society: 63–129. https://doi.org/10.1080/25761900.2022.12131791 Hyatt A. 1883–1884. Genera of fossil cephalopods. Proceedings of the Boston Society of Natural History 22: 253–338. Hyatt A. 1891. Carboniferous cephalopods. Annual Report of the Geological Survey of Texas 2: 327–356. European Journal of Taxonomy 1017: 1–85 (2025) 82 Hyatt A. 1894. Phylogeny of an acquired characteristic. Proceedings of the American Philosophical Society 32: 349–647. https://doi.org/10.5962/bhl.title.59826 Hyatt A. 1898. A new classification of fossil cephalopods. Proceedings of the American Association for the Advancement of Science 47: 363–365. Hyatt A. 1900. Cephalopoda. In: Zittel K.A.von & Eastman C.R. (eds) Text-book of Palaeontology, Volume 1, 1st Edition: 502–604. Macmillan, London, New York. King A.H. 1993. Mollusca: Cephalopoda (Nautiloidea). The Fossil Record 2: 169–188. King A.H. & Evans D.H. 2019. High-level classification of the nautiloid cephalopods: a proposal for the revision of the Treatise Part K. Swiss Journal of Palaeontology 138: 65–85. https://doi.org/10.1007/s13358-019-00186-4 Klug C., Korn D., Landman N.H., Tanabe K., De Baets K. & Naglik C. 2015. Describing ammonoid conchs. In: Klug C., Korn D., De Baets K., Kruta I. & Mapes R.H. (eds) Ammonoid Paleobiology: From Macroevolution to Paleogeography, Topics in Geobiology 44: 3–24. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-9630-9_1 Korn D. 2010. A key for the description of Palaeozoic ammonoids. Fossil Record 13: 5–12. https://doi.org/10.1002/mmng.200900008 Korn D. & Bockwinkel J. 2022. Early Carboniferous nautiloids from the Central Sahara, southern Algeria. European Journal of Taxonomy 831: 67–108. https://doi.org/10.5852/ejt.2022.831.1871 Korn D. & Ghaderi A. 2025. Late Permian nautiloids from Julfa. European Journal of Taxonomy 1018: 1–113. https://doi.org/10.5852/ejt.2025.1018.3069 Korn D. & Hairapetian V. 2025. Late Permian nautiloids from Baghuk Mountain. European Journal of Taxonomy 1019: 1–76. https://doi.org/10.5852/ejt.2025.1019.3071 Korn D. & Ilg A. 2007. AMMON. Database of Palaeozoic Ammonoidea. Available from http://www.wahre-staerke.com/ammon/ [accessed 6 Jun. 2025]. Korn D. & Klug C. 2023. Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco). European Journal of Taxonomy 885: 156–194. https://doi.org/10.5852/ejt.2023.885.2199 Kummel B. 1953. American Triassic coiled nautiloids. Professional Papers, U.S. Geological Survey 250: 1–104. https://doi.org/10.3133/pp250 Kummel B. 1963. Miscellaneous nautilid type species of Alpheus Hyatt. Bulletin of the Museum of Comparative Zoology 128: 325–-368. Kummel B. 1964. Nautiloidea-Nautilida. In: Moore R.C. (ed.) Treatise on Invertebrate Paleontology: K383–K466. The Geological Society of America and The University of Kansas Press, Lawrence, KS. Leonova T.B. & Shchedukhin A.Y. 2023. New Nautilida from the Shakhtau Asselian–Sakmarian Reef Complex (Bashkortostan). Paleontological Journal 57: 380–391. https://doi.org/10.1134/S003103012304007X Liang X. 1984. Some nautiloids of Late Permian. Acta Palaeontologica Sinica 23: 699–704. M‘Coy F. 1844. A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland. University Press, Dublin. https://doi.org/10.5962/bhl.title.11559 Maillieux E. 1925. Note sur quelques céphalopodes des terrains paléozoiques de la Belgique. Bulletin de la Société belge de Géologie 34: 34–41. Meek F.B. & Worthen A.H. 1873. Descriptions of invertebrates from Carboniferous system. Illinois Geological Survey Bulletin 5: 321–619. KORN D., A revised classification of the Carboniferous and Permian Nautilida 83 Miao L., Dai X., Korn D., Brayard A., Chen J., Liu X. & Song H. 2021. A Changhsingian (Late Permian) nautiloid assemblage from Gujiao, South China. Papers in Palaeontology 7: 329–351. https://doi.org/10.1002/spp2.1275 Mikesh D.L. & Glenister B.F. 1966. Solenochilus springeri (White & St. John, 1868) from the Pennsylvanian of southern Iowa. Proceedings of the Iowa Academy of Science 73: 269–278. Miller A.K. 1945. Permian nautiloids from the Glass Mountains and the Sierra Diablo of west Texas. Journal of Paleontology 19: 282–294. Miller A.K. & Collinson C. 1953. An aberrant nautiloid of the Timor Permian. Journal of Paleontology 27: 293–295. Miller A.K. & Furnish W.M. 1939. Lower Mississippian nautiloid cephalopods of Missouri. In: Branson E.B. & Mehl M.G. (eds) Stratigraphy and Paleontology of the Lower Mississippian of Missouri. University of Missouri Studies 13: 149–178. Columbia, Mo. Miller A.K. & Furnish W.M. 1955. The Carboniferous guide fossil, Tylonautilus, in America. Journal of Paleontology 29: 462–464. Miller A.K. & Garner H. 1953. Lower Mississippian cephalopods of Michigan. Part II. Coiled nautiloids. Contributions of the Museum of Paleontology, University of Michigan 11: 111–151. Miller A.K. & Owen J.B. 1934. Cherokee nautiloids of the northern Mid-Continent region. University of Iowa Studies in Natural History 16: 185–272. Miller A.K. & Unklesbay A.G. 1942. Permian nautiloids from western United States. Journal of Paleontology 16: 719–738. Miller A.K. & Youngquist W.L. 1949. American Permian nautiloids. Geological Society of America Memoires 41: 1–28. https://doi.org/10.1130/MEM41-p1 Miller A.K., Dunbar C.O. & Condra G.E. 1933. The nautiloid cephalopods of the Pennsylvanian system in the Mid-Continent region. Nebraska Geological Survey Bulletin 9: 1–240. Mojsisovics E.v.M. 1902. Das Gebirge um Hallstatt. Die Cephalopoden der Hallstätter Kalke. 1. Band. Abhandlungen der kaiserlichen und königlichen geologischen Reichsanstalt 6: 175–356. Murphy J.L. 1966. The Pennsylvanian Nautiloid Kionoceras ungeri (Sturgeon & Miller). Journal of Paleontology 40: 1388–1390. Niko S. & Mapes R.H. 2011. Texanoceras, a new neptunoceratid cephalopod genus from the Upper Pennsylvanian Graham and Caddo Creek Formations in north-central Texas. Journal of Paleontology 85: 519–523. https://doi.org/10.1666/10-048.1 Prinoth H. & Posenato R. 2007. Late Permian nautiloids from the Bellerophon Formation of the Dolomites (Italy). Palaeontographica Abteilung A 282: 135–165. https://doi.org/10.1127/pala/282/2007/135 Qin Z. 1986. New material of early Late Permian cephalopods in Fengcheng-Gaoan area, Jiangxi. Acta Palaeontologica Sinica 25: 272–283. Ruzhencev V.E. & Shimansky V.N. 1954. Nizhnepermskie svernutye i sognutie nautiloidei yuzhnogo Urala. Trudy Paleontologicheskogo Instituta. Akademiya Nauk SSSR 50: 1–152. [In Russian.] Schindewolf O.H. 1951. Über ein neues Vorkommen unterkarbonischer Pericyclus-Schichten im Oberharz. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 93: 23–116. Schmidt H. 1951. Nautiliden aus deutschem Unterkarbon. Paläontologische Zeitschrift 24: 23–57. https://doi.org/10.1007/BF03044551 European Journal of Taxonomy 1017: 1–85 (2025) 84 Schréter Z. 1974. Die Nautiloiden aus dem oberen Perm des Bükkgebirges. In: Sidó M., Zalányi B. & Schréter Z. (eds) Neue paläontologische Ergebnisse aus dem Oberpaläozoikum des Bükkgebirges: 253– 311. Akadémia Kiadó, Budapest. Shevyrev A.A. 2006. The cephalopod macrosystem: A historical review, the present state of knowledge, and unsolved problems: 2. Classification of nautiloid cephalopods. Paleontological Journal 40: 46–54. https://doi.org/10.1134/S0031030106010059 Shimansky V.N. 1957. Sistematika i filogeniya otryada Nautilida. Byulleten’ Moskovskogo obshchestva ispytatelei prirody. Otdel geologicheskiy 32: 105–120. [In Russian.] Shimansky V.N. 1962. Nadotryad Nautiloidea. Nautiloidei. Sistematicheskaya chast. Otryad Nautilida. In: Orlov Y.A. (ed.) Osnovy Paleontologii, Mollyuski - Golovonogie 1: 115–169. Akademiya Nauk SSSR, Moskva. [In Russian.] Shimansky V.N. 1965. Podotryad Nautiloidea. Trudy Paleontologicheskogo Instituta. Akademiya Nauk SSSR 108: 157–165. [In Russian.] Shimansky V.N. 1967. Kamennougol’nie Nautilida. Trudy Paleontologicheskogo Instituta. Akademiya Nauk SSSR 115: 1–258. [In Russian.] Shimansky V.N. 1974. Order Nautilida. In: Hardin H. (ed.) Fundamentals of Paleontology (Osnovy Paleontologii). Vol. 5, Molluska - Cephalopoda 1: 159–227. Keter Publishing House, Jerusalem. Shimansky V.N. 1979. Nautilida (izuchennost’, stratigraficeskoe rasprostranenie, etapy razvitiya). Trudy Paleontologicheskogo Instituta. Akademiya Nauk SSSR 170: 1–67. [In Russian.] Simić V. 1933. Gornji Perm u Zapadnoj Srbiji (Das Oberperm in Westserbien). Rasprave Geološkog Instituta Kraljevine Jugoslavije (Mémoires du Service géologique du Royaume de Yougoslavie) 1: 1–130. [In Serbian.] Sobolev E.S. 1989. Triasovye nautilidy severo-vostochnoy Azii. Trudy Instituta Geologii I Geofiziki, Akademiya Nauk SSSR, Sibirskoe Otdelenie 727: 1–193. [In Russian.] Sowerby J. 1812–1815. The Mineral Conchology of Great Britain: Or Coloured Figures and Descriptions of those Remains of Testaceous Animals or Shells, which have been Preserved at Various Times and Depths in the Earth. Vol. I. Meredith, London. https://doi.org/10.5962/bhl.title.14408 Sowerby J.D.C. 1823–1825. The Mineral Conchology of Great Britain; or Coloured Figures and Descriptions of those Remains of Testaceous Animals or Shells, which have been Preserved at Various Times and Depths in the Earth. Vol. V. Richard Taylor, London. Sturgeon M.T. & Miller A.K. 1948. Some additional cephalopods from the Pennsylvanian of Ohio. Journal of Paleontology 22: 75–80. Sturgeon M.T., Windle D.L., Mapes R.H. & Hoare R.D. 1982. New and revised taxa of Pennsylvanian cephalopods in Ohio and West Virginia. Journal of Paleontology 56: 1453–1479. Sturgeon M.T., Windle D.L., Mapes R.H. & Hoare R.D. 1997. Pennsylvanian Cephalopods of Ohio. Part 1. Nautiloid and Bactritoid Cephalopods. Ohio Division of Geological Survey, Bulletin 71: 1–191. Teichert C. 1964a. Doubtful taxa. In: Moore R.C. (ed.) Treatise on Invertebrate Paleontology: K484– K490. The Geological Society of America and The University of Kansas Press, Lawrence, KS. Teichert C. 1964b. Morphology of hard parts. In: Moore R.C. (ed.) Treatise on Invertebrate Paleontology: K13–K53. The Geological Society of America and The University of Kansas Press, Lawrence, KS. Teichert C. & Kummel B. 1973. Nautiloid cephalopods from the Julfa Beds, Upper Permian, Northwest Iran. Bulletin of the Museum of Comparative Zoology, Harvard University 144: 409–434. KORN D., A revised classification of the Carboniferous and Permian Nautilida 85 Trenkner W. 1868. Palaeontologische Novitäten vom nordwestlichen Harze. I. Iberger Kalk und Kohlengebirge von Grund. Abhandlungen der Naturforschenden Gesellschaft zu Halle 10: 123–182. Turner J.S. 1954. On the Carboniferous nautiloids: some Middle Viséan species from the Isle of Man. Liverpool and Manchester Geological Journal 1: 298–325. https://doi.org/10.1002/gj.3350010307 Turner J.S. 1965. On the Carboniferous nautiloids: Nautilus quadratus Fleming and certain other coiled nautiloids. Proceedings of the Leeds Philosophical and Literary Society 9: 223–256. Turner J.S. 1966. On the Carboniferous nautiloids: the Phacoceratidae. Proceedings of the Leeds Philosophical and Literary Society 10: 1–5. von Arthaber G. 1900. Das jüngere Paläozoicum aus der Araxes-Enge bei Djulfa. Beiträge zur Paläontologie und Geologie Österreich-Ungarns und des Orients 12: 209–302. Waagen W. 1879. Salt Range fossils, 1. Productus Limestone fossils. Palaeontologia Indica 1: 1–85. Xu G. 1977. Cephalopoda. In: Fossil Atlas of South-Central China: 537–582. Yin T.H. 1933. Cephalopoda of the Penchi and Taiyuan Series of North China. Palaeontologia Sinica, Series B 11: 1–32. Zhao J., Liang X. & Zheng Z. 1978. Late Permian cephalopods from South China. Palaeontologia Sinica, Series B 12: 1–194. Zheng Z. 1984. Late Permian nautiloids from western Guizhou. Acta Palaeontologica Sinica 23: 239– 253. Printed versions of all papers are deposited in the libraries of four of the institutes that are members of the EJT consortium: Muséum national dʼHistoire naturelle, Paris, France; Meise Botanic Garden, Belgium; Royal Museum for Central Africa, Tervuren, Belgium; Royal Belgian Institute of Natural Sciences, Brussels, Belgium. The other members of the consortium are: Natural History Museum of Denmark, Copenhagen, Denmark; Naturalis Biodiversity Center, Leiden, the Netherlands; Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain; Leibniz Institute for the Analysis of Biodiversity Change, Bonn – Hamburg, Germany; National Museum of the Czech Republic, Prague, Czech Republic; The Steinhardt Museum of Natural History, Tel Aviv, Israël.