New data on the mammalian fauna from the late middle Eocene (MP 15–16) of Mazaterón (Soria, Spain): The youngest presence of the genus Prodissopsalis (Hyaenodonta, Hyaenodontidae) in Europe

SPECIAL ISSUE ARTICLE New data on the mammalian fauna from the late middle Eocene (MP 15–16) of Mazater on (Soria, Spain): The youngest presence of the genus Prodissopsalis (Hyaenodonta, Hyaenodontidae) in Europe Manuel J. Salesa 1 | Gema Siliceo 1,2 | Mauricio Ant on 1 | Irene Martínez 1 | Francisco Ortega 3 1 Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain 2 Faculty of Natural Science, Department of Geology and Paleontology, Comenius University, Bratislava, Slovak Republic 3 Grupo de Biología Evolutiva, Universidad Nacional de Educaci on a Distancia (UNED), Madrid, Spain Correspondence Manuel J. Salesa, Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, C/José Gutiérrez Abascal, 2, 28006 Madrid, Spain. Email: [email protected] Funding information EVOFEL funded by MCIN/ AEI/10.13039/501100011033, Grant/Award Number: PID2020-112642GB-I00 Abstract The Hyaenodonta were the most diverse carnivorous mammals in the European Eocene and were classically divided into three subfamilies: Sinopaninae, Arfianinae, and Proviverrinae, with this latter being the most successful of the three, as it exhibited a much larger geographic and temporal range. This classification is currently abandoned, as cladistic analyses of Hyaenodonta showed that several of these groups were paraphyletic. In any case, the former “proviverrines”were European endemic hyaenodontids which occupied the niche of small to medium-sized predators from the Ypresian (MP7) to the Priabonian (MP19). Recent phylogenetic proposals recognize the “Eurotherium clade”including this latter genus, besides Cartierodon and Prodissopsalis. A single species is known for Prodissopsalis,Prodissopsalis eocaenicus, previously recorded in European fossil sites of MP 12 to MP 14; nevertheless, the new material studied here, a mandible of a subadult individual from the late Middle Eocene (Bartonian, MP 15–16) site of La Solana (Mazater on, Soria, Spain) constitutes a new species of Prodissopsalis and the youngest record of this genus up to now, extending its chronological range and remarking the shelter role of the northwestern region of the Iberian Peninsula during the Middle and Late Eocene. The new species, Prodissopsalis jimenezi provides new data not only on the eruption sequence of the genus, but also on the evolution of its dental adaptations, as the new species exhibits a more trenchant, hypercarnivorous dentition in comparison to the more primitive species P. eocaenicus, which would point toward a refining of the hunting abilities of this hyaenodont during the Middle Eocene. KEYWORDS Bartonian, endemic faunas, Eocene, Hyaenodonta, Spain Received: 7 February 2023 Revised: 29 March 2023 Accepted: 29 March 2023 DOI: 10.1002/ar.25223 This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2023 The Authors. The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy. Anat Rec. 2023;1–14. wileyonlinelibrary.com/journal/ar 1 1|INTRODUCTION During the Paleogene (66–23 Mya), several lineages of mammals competed for occupy the niche of terrestrial carnivorous predators: Carnivoramorpha (where the modern order Carnivora is included), Hyaenodonta, Mesonychia, and Oxyaenodonta (Friscia & Van Valkenburgh, 2010; Radinsky, 1982; Savage, 1977;Soléetal.,2022;Van Valkenburgh, 1999). Although the former group was the only one to persist in the extant mammalian faunas, these four clades were sympatric in most of the ecosystems of North America and Eurasia from the beginning of the Paleocene to the Middle Eocene, when carnivoramorphans finally became the dominant predators (Flynn & Wesley-Hunt, 2005;Friscia&Van Valkenburgh, 2010; Morlo et al., 2010;Morlo& Nagel, 2007;Rose,2006; Savage, 1977;Soléetal.,2022; Van Valkenburgh, 1999). Although members of these four clades are considered to have a primarily carnivorous diet, only three of them (Carnivoramorpha, Hyaenodonta, and Oxyaenodonta) developed “carnassial teeth,”that is, at least one pair of specialized teeth (one upper and one lower), with elongated crests that, when occluding, function as scissors, slicing the meat and cutting the skin and tendons of prey (Ewer, 1973; Flynn & Wesley-Hunt, 2005; Solé & Ladevèze, 2017; Van Valkenburgh, 1989). The FIGURE 1 Geological map of the Duero Basin and location of the fossil vertebrate site of La Solana. (a) Location of Castilla y Le on autonomous community (dark gray) within Spain (light gray), showing the locations of Madrid and Soria cities. (b) Geological map of the Almaz an Basin showing the location of the La Solana fossil site (modified from Ortega et al., 2022; Rodríguez Fern andez et al., 2015). 2SALESA ET AL. 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License fourth carnivorous clade, the Mesonychia, did not have proper carnassial teeth; instead, its members developed a peculiar molar morphology that showed a progressive modification toward a premolar-like structure (Russell, 1954). Both Hyaenodontidae and Oxyaenodonta were previously considered superfamilies within the order “Creodonta,”a heterogeneous group that was supposed to have a common origin (Ginsburg, 1999). Nevertheless, several studies strongly suggested that these two groups show similar morphological features and ecological roles by simply convergence, rather than due to a phylogenetical relationship (Morlo et al., 2009; Polly, 1994; Rose, 2006; Zack, 2019a). Solé (2013) proposed the use of the order Hyaenodonta, named by Van Valen (1967), which included the family Hyaenodontidae, although the use of Creodonta as an order was considered valid for other authors such as Friscia and Van Valkenburgh (2010). In this paper, we follow the proposal of Solé (2013), and we prefer to discard the use of the paraphyletic clade Creodonta. The European mammalian faunas of the early Eocene (around 56 Ma) included Hyaenodontidae classically included in the subfamilies Sinopaninae, Arfianinae, and Proviverrinae, besides several genera of less clear adscription, such as Cynohyaenodon,Eurotherium,or Matthodon (Godinot, 1981; Godinot et al., 1987; Hooker, 2010;Rich,1971; Smith & Smith, 2001; Solé, 2013;Soléetal.,2013). Nevertheless, sinopanines and arfianines went extinct during the Late Ypresian, around 50 Ma ago (Solé et al., 2014), whereas the rest of these European Hyaenodontoidea exhibited a much longer temporal range, in fact being recorded during the rest of the European Eocene (Solé et al., 2013, 2014). Nevertheless, the use of these subfamily-level names has been called into question due to several phylogenetic analysis that tried to clarify the actual relationships between the different groups (Borths & Stevens, 2017a,2017c,2019a,2019b;Soléetal.,2020, 2021;Solé&Mennecart,2019;Zack,2019b). In fact, Solé (2013) already suggested that the use of ProviverrinaeshouldberestrictedtosomeEuropeanhyaenodontids with clear phylogenetic affinities, such as the genera Proviverra,Allopterodon,Cynohyaenodon,Lesmesodon,orProdissopsalis, and later phylogenetic analyses (Borths et al., 2016;Borths&Seiffert,2017; Borths & Stevens, 2017a,2017c,2019a) suggested that proviverrines could be a paraphyletic group. Also, in a recent revision of the group, Solé & Mennecart (2019) rejected the monophyly of “Proviverrinae”sensu Solé (2013), considering this group as part of the stem lineages of Hyaenodontinae, and grouping Hyaenodontidae, and “Proviverrinae”in Hyaenodontoidea (Solé et al., 2021;Solé&Mennecart,2019). Finally, Solé et al. (2021) has proposed restricting the use of “Proviverrinae”to a clade within Hyaenodontoidea containing only Proviverra,Allopterodon,Morlodon,Lesmesodon,andParvagula, which these authors called “Proviverra/Allopterodon clade,”whereas the genera Eurotherium,Prodissopsalis,andCartierodon would conform the “Eurotherium clade,”with no close relationship to the “Proviverra/Allopterodon clade.” Here, we will follow this taxonomical proposal of Solé et al. (2021). Within the Eurotherium clade, Prodissopsalis eocaenicus is recorded in European fossil sites from MP 12 to 14 (Calas, 1969,1970; LangeBadré, 1972; Lange-Badré & Haubold, 1990; Matthes, 1952; Morlo & Habersetzer, 1999;Solé& Mennecart, 2019), but the new material studied here, fromtheSpanishlatemiddleEocene(Bartonian,MP 15–16)siteofLaSolana(Mazater  on, Soria province) extends the chronological record of this genus up to around 41 Ma. This new taxon was a large to very large hyaenodont, following the categories by Morlo (1999), with an estimated maximum body weight of 30 kg (Morlo et al., 2010). The Bartonian (late middle Eocene) fossil site of La Solana (Figure 1) is located 2.5 km northeast from the village of Mazater on, in the Soria province (Spain), within the Mazater on Formation of the Almaz an Basin (Badiola et al., 2022). Although the inhabitants of this small village had known since many years ago about the existence of fossils in that spot, it was not until 1987 when the La Solana fossil site was intensively surveyed by Prof. Emiliano Jimenez (Cuesta Ruiz-Colmenares & Jiménez Fuentes, 1994). The vertebrate fossils from La Solana are found within a layer of gray marls that form part of a series of lacustrine-palustrine deposits, basically limestones and marls (Perales-Gogenola et al., 2021). These levels were formed in a shallow lacustrine system, which experienced recurrent flooding and drying processes (Alonso-Gavil an et al., 2004; Huerta & Armenteros, 2006). During the lower Ypresian (early Eocene), the faunal associations of mammals and reptiles from the Iberian Peninsula were very similar to those of the rest of Europe, which by that time, and due to a series of marine transgressions, had become a vast and fragmented archipelago (Egger et al., 2013; Rougier et al., 2016). But, in the lower Lutetian (lower middle Eocene, MP 11) the northwestern region of the Iberian Peninsula was isolated from both the eastern region and the rest of Europe, and thus, the known faunas from the latest middle and earliest upper Eocene (Bartonian and Priabonian) show a marked endemism (Bolet, 2017; Ortega et al., 2022). SALESA ET AL.3 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 2|MATERIALS AND METHODS 2.1 |Studied specimen The specimen studied in this paper is a mandible (catalogue number STUS-15077) from the late middle Eocene (MP 15–16) site of La Solana (Mazater on, Soria province, Spain), housed at the paleontological collections of fossil vertebrates from the Duero Basin (Sala de las Tortugas) of the Universidad de Salamanca (Salamanca, Spain). We follow the dental nomenclature of Szalay (1969). 2.2 |Acquisition and processing of the data The mandible STUS-15077 was scanned on a CTScan Nikon-XTH 160 at the Service of Non-Destructive Techniques of the MNCN-CSIC with the following parameters: 160 kv, 159 μA, and a resolution of 0.073 mm. The 3D virtual models were obtained through the software VGStudio MAX 3.0 (Volume Graphics GmbH) and 3D Slicer 4.10.1. To obtain 3D virtual models of different teeth the tomographs were processed following a semiautomatic protocol for segmentation based on the thresholding method. Measurements of STUS-15077 were taken with a digital caliper to the nearest 0.1 mm. They are provided in Tables 1and 2, besides those of different species of Hyaenodonta for comparison. 2.3 |Abbreviations The following abbreviations are used throughout the text and figures: c, lower canine; i2, second lower incisor; i3, third lower incisor; dp4, deciduous fourth lower premolar; p1, first lower premolar; p1a, alveolus for p1; p2, second lower premolar; p3, third lower premolar; p4, fourth lower premolar; m1, first lower molar; m2, second lower molar; m3, third lower molar; BLW, buccolingual width; End, entoconid; Hyld, hypoconulid; Hyd, hypoconid; MDL, mesiodistal length; Med, metaconid; mf, mental foramina; tb, talonid basin; Pad, paraconid; PPac, postparacristid; PPrc, preprotocristid; Prd, protoconid; STUS, Sala de las Tortugas de la Universidad de Salamanca. 3|SYSTEMATIC PALEONTOLOGY Class Mammalia Linnaeus, 1758 Order Hyaenodonta Van Valen, 1967 TABLE 1 Measurements in mm of the m1 of different species of Hyaenodonta. Species Site m1 MDL m1 BLW Data source Prodissopsalis jimenezi La Solana 11.33 6.05 This work Eurotherium matthesi Geiseltal 8.20 4.60 Lange-Badré and Haubold (1990) Eurotherium matthesi Geiseltal 8.90 4.70 Lange-Badré and Haubold (1990) Oxyaenoides bicuspidens Geiseltal 10.50 —Lange-Badré and Haubold (1990) Oxyaenoides bicuspidens Geiseltal 10.90 5.50 Lange-Badré and Haubold (1990) Oxyaenoides bicuspidens Palassou 12.30 6.10 Lange-Badré and Haubold (1990) Matthodon tritens Geiseltal 11.20 6.40 Lange-Badré and Haubold (1990) Matthodon tritens Geiseltal 12.40 6.50 Lange-Badré and Haubold (1990) Matthodon tritens Geiseltal 12.40 6.70 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 11.70 7.10 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 12.70 6.10 Lange-Badré and Haubold (1990) Cynohyaenodon trux Egerkingen γ6.30 —Lange-Badré and Haubold (1990) Cynohyaenodon trux Egerkingen γ5.50 3.20 Lange-Badré and Haubold (1990) Proviverra typica Egerkingen γ4.30 2.50 Lange-Badré and Haubold (1990) Cartierodon egerkingensis Egerkingen γ14.00 7.40 Solé and Mennecart (2019) Paracynohyaenodon schlosseri Les Clapiés 7.60 4.70 Lange-Badré and Mathis (1992) Paracynohyaenodon schlosseri Robiac 7.90 4.80 Lange-Badré and Mathis (1992) Paracynohyaenodon schlosseri Robiac 7.10 4.20 Lange-Badré and Mathis (1992) Paracynohyaenodon schlosseri Robiac 7.70 4.70 Lange-Badré and Mathis (1992) 4SALESA ET AL. 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Family Hyaenodontidae Leidy, 1869 Genus Prodissopsalis Matthes, 1952 Type species. Prodissopsalis eocaenicus Matthes, 1952. Type locality. Geiseltal-Obere Mittelkohle, Grube Leonhardt, Site III (MP 12, Germany). Holotype. Leo III-94 (LH94), fragment of skull with right P1-P4 and M1-M3, and left M1-M3, figured in Matthes (1952, figs. 1–3). Distribution. Geiseltal-Untere Mittelkohle (Lutetian, MP 12, Germany) and Geiseltal-Obere Mittelkohle (Lutetian, MP13, Germany); Issel (Lutetian, MP 14, France); Lissieu (Lutetian, MP 14, France); and Egerkingen α+ß (Lutetian, MP 14, Switzerland). Emended diagnosis. Modified from Lange-Badré and Haubold (1990): “Proviverrine”of large size, with dental formula 2/? I, 1/1 C, 4/4 P, 3/3 M; P1, P2 and P3 with low and mesiodistally elongated crown, slightly separated but without defining a diastema; double-rooted P1 and p1 single or double-rooted depending on the species; crown of P3 distolingually expanded and shorter than that of P2; P4 with a lingually elongated protocone; p4 with hypoconid and entocristid; m1 and m2 with a moderately reduced metaconid, partially fused to the high and narrow protoconid, paraconid height larger than its mesiodistal length; high talonid with a swallow basin; hypoconid forming a buccal rib, widely separated from the hypoconulid; entoconid not distinct from the entocristid; presence of a postcingulid close to the hypoconulid; m3 with a more reduced metaconid and a longer and more mesially located paraconid than those of m1 and m2; triangular talonid with an entocristid contacting the hypoconulid. Upper molars with paracone smaller and lower than metacone; metastyle high in relation to the metastyle, and not aligned with the metacrista; length of metastyle similar to that of the two buccal cusps; protocone mesially located; M3 with a long parastyle and a very small metacone. Prodissopsalis jimenezi new species Figures 3–5, Tables 1and 2 Type locality. La Solana (Mazater on, Soria province, Spain), late middle Eocene (Bartonian, MP 15–16). Holotype. STUS-15077, fragmented mandible with both right and left rami, with erupting left d4 and m2, TABLE 2 Measurements in mm of the m2 of different species of Hyaenodonta. Species Site m2 MDL m2 BLW Data source Prodissopsalis jimenezi La Solana 14.81 5.67 This work Eurotherium matthesi Geiseltal 9.00 5.40 Lange-Badré and Haubold (1990) Eurotherium matthesi Geiseltal 9.20 5.50 Lange-Badré and Haubold (1990) Eurotherium matthesi Geiseltal 9.90 5.70 Lange-Badré and Haubold (1990) Oxyaenoides bicuspidens Geiseltal 12.30 6.20 Lange-Badré and Haubold (1990) Oxyaenoides bicuspidens Geiseltal 13.10 6.70 Lange-Badré and Haubold (1990) Oxyaenoides bicuspidens Palassou 12.70 8.10 Lange-Badré and Haubold (1990) Matthodon tritens Geiseltal 13.50 7.80 Lange-Badré and Haubold (1990) Matthodon tritens Geiseltal 14.30 8.10 Lange-Badré and Haubold (1990) Matthodon tritens Geiseltal 14.80 8.30 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 12.70 7.20 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 13.40 7.00 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 13.90 7.20 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 14.10 8.10 Lange-Badré and Haubold (1990) Prodissopsalis eocaenicus Geiseltal 14.40 7.90 Lange-Badré and Haubold (1990) Cynohyaenodon trux Geiseltal 6.20 3.40 Lange-Badré and Haubold (1990) Cynohyaenodon trux Geiseltal 6.00 —Lange-Badré and Haubold (1990) Cynohyaenodon trux Geiseltal 7.10 —Lange-Badré and Haubold (1990) Cynohyaenodon trux Geiseltal —4.10 Lange-Badré and Haubold (1990) Cynohyaenodon trux Egerkingen γ5.80 3.70 Lange-Badré and Haubold (1990) Proviverra typica Egerkingen γ4.40 2.70 Lange-Badré and Haubold (1990) Proviverra typica Egerkingen γ4.60 3.10 Lange-Badré and Haubold (1990) Cartierodon egerkingensis Egerkingen γ13.10 8.00 Solé and Mennecart (2019) Cartierodon egerkingensis Egerkingen γ15.20 8.90 Solé and Mennecart (2019) SALESA ET AL.5 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License and right dp4, m1 and m2; the c, p2, p3, p4 and m3 of both sides are still inside the mandibular bone, but only the right i2 and i3 are preserved; all of them were studied through CT Scanning of the piece. Zoobank species LSID: urn:lsid:zoobank.org: act:87759DAB-B6DA-4D70-87FD-127AE66030DD. Etymology. The species name is dedicated to Prof. Emiliano Jiménez Fuentes, who greatly contributed to the knowledge of the Eocene fossil record from Spain. Diagnosis. Very similar size to P. eocaenicus, with dental formula ?/2 I, ?/1 C, ?/4 P, ?/3 M; dp4 with elongated and buccolingually compressed crown, without cingulids, paraconid lower than protoconid and mesially oriented, metaconid moderately developed, slightly higher that paraconid, low buccodistally oriented talonid, with a marked central basin, and talonid cuspids crested, with a hypoconid higher than entoconid and hypoconulid; single-rooted p1; p4 with hypoconid; m1 with low paraconid, much higher protoconid, well-developed metaconid located at the level of the distal border of the protoconid, paraconid mesiolingually oriented and with a vertical buccal ridge, talonid much shorter than trigonid, deep talonid basin, with entoconid, hypoconid and hypoconulid clearly individualized, the latter being slightly higher than the two others; m2 larger and relatively much higher than both m1 and dp4, with a mesiodistally elongated and buccolingually compressed crown, protoconid much higher than paraconid, which is mesiolingually oriented, very reduced talonid in comparison to m1, with round hypoconulid and a slightly lower hypoconid. Differential diagnosis. P. jimenezi can be distinguished from P. eocaenicus by the following features: single-rooted p1, relatively more elongated paracristid in m1 and m2, relatively more compressed m1 and m2, relatively reduced talonid on m1. FIGURE 2 STUS-15077, mandible of Prodissopsalis jimenezi from La Solana: (a) right lateral view, (b) left lateral view, and (c) occlusal view. Abbreviations in Section 2. 6SALESA ET AL. 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 4|DESCRIPTION OF THE MAZATERÓN SPECIMEN 4.1 |Mandible The specimen is very fragmented, and it lacks most of the coronoid process (Figure 2). The mandibular corpus is elongated, with a gently curved symphysis, and two mental foramina, similarly sized, slightly rostrocaudally elongated, and located at the level of p2 and p3 (Figure 2a). The caudal border is broken, but the remaining ventral border of the angular process shows the existence of a slightly curved outline. These two features (two mental foramina and curved caudal margin) are typical of Hyaenodontidae (Solé, Amson, et al., 2015). 4.2 |Lower dentition The right i2 and i3 are partially unerupted; the crowns are formed but the roots were not fully developed when the animal died (Figure 3); the crown of both pieces is very similar in morphology and size: there is a main central cuspid, mesially displaced, a less developed distal cuspid, and a very small, vestigial mesial cuspid. The lower canines, with a blunt point, are in a very early development stage, so only a small portion of the crown is formed; this is buccolingually compressed, and showing a lingual longitudinal groove for the accommodation of the permanent canines, although there is no trace of them. The alveoli of both left and right p1 are visible, although these pieces are not preserved in the specimen; from the alveolus, it seems that the p1s were singlerooted (Figure 3c). The p2s have partially developed roots, as these teeth are in an early stage of development, showing only the tip of the main cuspid; their crowns are triangular, with a very elongated distal border, and are slightly buccolingually compressed and lingually curved; there are no mesial or distal cuspids, but there are soft mesial and distal ridges instead. Both p3s and p4s are unerupted. The p3s are much smaller than p2 and p4, but they seem to be in an earlier stage of development than these other premolars, which could explain their relatively smaller size; the crowns of both p3s are triangular, but more symmetrical than those of p2, as they lack the distal expansion seen on p2; also, the crown is not compressed but inflated. The p4s have a large and relatively high main cuspid, a very low buccodistal cuspid (a hypoconid for Lange-Badré & Haubold, 1990), and an FIGURE 3 Rendering 3D image of STUS-15077, mandible of Prodissopsalis jimenezi from La Solana, rendered transparent to show the erupted and developing dentition in (a) right lateral view and (b) occlusal view. (c) Occlusal view of the rendered mandible to show the erupting dentition and alveoli. Abbreviations in Section 2. FIGURE 4 STUS-15077, right m1 of Prodissopsalis jimenezi from La Solana: (a) occlusal view, (b) buccal view, and (c) lingual view. Abbreviations in Section 2. SALESA ET AL.7 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License almost absent mesial cuspid; the crown is much larger than that of p3, but slightly smaller than p2; in a similar way to this latter tooth, the crown of p4 is buccolingually compressed. In this respect, it should be noted that p2, p3, and p4 are in different stages of development, but none of them has reached its definitive morphology, and thus the mentioned differences in relative size should be taken with caution until a mandible with a completely erupted adult dentition is found. The dp4s have elongated and buccolingually compressed crowns, without any trace of cingulids; the paraconid is lower than the protoconid and is mesially oriented; the metaconid is moderately developed, located slightly higher that the paraconid; the talonid is low, buccodistally oriented, with a marked central basin; the talonid cuspids are crested, with a hypoconid higher than entoconid and hypoconulid. The m1 (Figure 4)hasalow paraconid and a much higher protoconid, with a welldeveloped metaconid located at the level of the distal border of the protoconid, slightly higher than the paraconid; this latter is oriented mesiolingually and its buccal surface develops a marked vertical ridge; the talonid is much shorter than the trigonid, and is distally oriented; the talonid basin is deep, and the entoconid, hypoconid and hypoconulid and are clearly individualized, with the latter being slightly higher than the two others. The dp4 and m1 are of similar size, both clearly smaller than m2. This latter molar is larger and relatively much higher than both m1 and dp4, and its crown is mesiodistally elongated and buccolingually compressed; the paraconid is much higher than the protoconid, which is mesiolingually oriented, although less so than the m1 protoconid; the talonid is very reduced in comparison to that of m1, and although it is severely broken, a round hypoconulid and a slightly lower hypoconid can be observed on the distolingual margin. The m3s are present, but unerupted and in a very early stage of development, and only the protoconid is clearly distinguishable in both sides. 4.3 |Eruption sequence in P. jimenezi The study of the eruption sequence of mammals can provide important data for phylogenetical and ontogenetical analysis (Bastl et al., 2011,2014; Bastl & Nagel, 2014; Borths & Stevens, 2017a). Nevertheless, for the description of the eruption sequence it is necessary to count with several specimens in different stage of development, which allows to infer the order of eruption of each dental piece. In general, to establish this eruption sequence, a tooth germ in a more advanced stage of formation is considered to erupt before other germs in an earlier stage, but for that purpose, a sample of fossils showing different phases of teeth development is necessary (Borths & Stevens, 2017a). In our case, only a single specimen is available from La Solana, and although it provides the first data on erupting teeth of a member of the Eurotherium-clade, the information is not enough to infer the complete sequence. The mandible STUS-15077 (Figure 3) does not preserve p1 (although the single-rooted alveolus confirms its presence), dp1, dp2, and dp3, but from the development stage of the permanent premolars and molars, it is clear that m1 and m2 were the first permanent teeth to erupt, and then probably the p2, which is located very close to the alveolar border of the mandible, and also shows a larger crown in a more advanced stage than those of p3 and p4; of these two latter premolars, the p3 shows a crown in a very early stage, as it is smaller than that of p4, which would suggest that the latter erupted earlier. Nevertheless, the crown of p3 is closer to the alveolar border than that of p4, and does not have a FIGURE 5 Comparison of the occlusal dentition in Prodissopsalis. (a) Occlusal view of GMH VI-211-1950, right hemimandible of P. eocaenicus from Geiseltal (MP 12–13, Germany). (b) STUS-15077, mandible of P. jimenezi from La Solana. Abbreviations in Section 2. 8SALESA ET AL. 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License deciduous premolar delaying its eruption, which is the case of p4; thus, this could imply a p3 erupting earlier than p4. More problematic is the case of m3, which is very close to the alveolar border, but shows a very incomplete crown that seems to illustrate the protoconid, with no trace of talonid and mesial part of trigonid; this would suggest, rather than a very early stage of development, the loss of part of the crown due to the poor state of preservation of STUS-15077, and thus the m3 would be closer to erupt than p4. Finally, the lower canine crown is as large as that of p2, but there is no other indication of its place in the sequence. Considering all this, the following tentative eruption sequence could be proposed for P. jimenezi: p1-m1-m2-p2-p3-m3-p4. This sequence is similar to those inferred by Borths and Stevens (2017a) for other Hyaenodonta, such as Apterodon,Masrasector,orMetasinopa. 5|DISCUSSION The fossil from La Solana shows several similarities with the material of P. eocaenicus from the older localities of Geiseltal (MP 12–13, Germany), and although the mandible studied here corresponds to a subadult individual, still far from the final adult stage, its overall shape and morphology, elongated and relatively slender, resemble those of the adult specimens from Geiseltal. The preserved dentition also illustrates the typical dental morphology of this genus and shows diagnostic features that allow its distinction from the closely related taxa Cartierodon egerkingensis, such as the smaller size, the relatively narrower lower premolars, and the absence of a mandibular foramen at the level of p4 (see Solé & Mennecart, 2019). Besides, the mandible from La Solana shows a very different morphology from that of other contemporary taxa such as Matthodon tritens, whose robust mandible and teeth (similarly to those of the genus Quercytherium) would point towards a scavenging, bone-cracking adaptation (Solé et al., 2014, 2015b). On the contrary, P. eocaenicus would belong to a group of more active hunters, which also included the more derived genus Oxyaenoides, this latter showing no trait of a metaconid in the lower molars and a strongly reduced talonid (Dubied et al., 2019). The m1 from La Solana shows a clearly individualized entoconid (Figure 4), a feature shared by other genera of hyaenodonts recorded in Ypresian and Lutetian localities from Europe, such as Proviverra,Cynohyaenodon,Eurotherium, Prodissopsalis,Leonhardtina,Allopterodon,Alienetherium, Quercytherium,andParacynohyaenodon (Solé & Mennecart, 2019), but its larger size (Tables 1and 2)and reduced talonid distinguishes the La Solana hyaenodont from other taxa with well-developed talonids on the lower molars, such as Leonhardtina,Allopterodon,Eurotherium, and Paracynohyaenodon. Following the phylogeny proposed by Solé & Mennecart (2019), P. eocaenicus is part of a clade containing the genera Eurotherium and Cartierodon, the three of them having a similar dental morphology, but also distinctive features: thus, Prodissopsalis shows a smaller size and a more reduced talonid on m1 and m2 than Cartierodon, traits also observed in the specimen from La Solana, whereas Cartierodon can be distinguished from Prodissopsalis by the presence of a second foramen located below the mesial root of the p4, wider lower premolars, mesiodistally shorter talonid on m3, and a protocone area more developed on P3 (Solé & Mennecart, 2019). Nevertheless, the material of from La Solana shows a set of morphological differences that allow its distinction from the known fossils of P. eocaenicus, such as the singlerooted p1 (in contrast to the double-rooted p1 of the latter), a relatively more elongated paracristid in m1 and m2, relatively more compressed m1 andm2,andastronglyreduced talonid on m1 (Figures 5and 6); these features indicate a derived dental morphology in relation to older specimens of this genus, something expectable given the great temporal gape existing between the last records of P. eocaenicus and the new fossils from La Solana site. Also, the dental differences suggest an evolution towards a more hypercarnivorous diet, with the reduction of p1 and more trenchant m1 and m2 (which both show elongated, sharper trigonids). Unfortunately, there are no published dp4 from P. eocaenicus, but this piece is known in other FIGURE 6 Comparison of the m1 in Prodissopsalis in occlusal view. (a) STUS-15077, right m1 of Prodissopsalis jimenezi from La Solana. (b) GMH VI-211-1950, right m1 of P. eocaenicus from Geiseltal (MP 12–13, Germany). Abbreviations in Section 2. SALESA ET AL.9 19328494, 0, Downloaded from https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25223 by Readcube (Labtiva Inc.), Wiley Online Library on [19/05/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License