New Leptolophus (Palaeotheriidae) species from the Iberian Peninsula and early evidence of hypsodonty in an Eocene perissodactyl

ABSTRACT

The middle and late Eocene perissodactyl fossil record of western Iberia is characterized by an endemic fauna, which is clearly different from those of northeastern Iberia and other areas of the European archipelago. In this work, we describe three endemic equoid taxa belonging to the family Palaeotheriidae. Two come from the late Eocene site of Zambrana (Miranda-Treviño Basin, Araba/Álava, Spain) and correspond to new species: Leptolophus cuestai, sp. nov., and Leptolophus franzeni, sp. nov. Leptolophus cuestai, sp. nov. is the largest species of Leptolophus and exhibits thick coronal cementum and a very high hypsodonty index, unusual for an Eocene equoid. Leptolophus franzeni, sp. nov. is described from a cranium which includes the canines, which are otherwise unknown in Leptolophus. The third taxon, from the late middle Eocene site of Mazaterón (Almazán Basin, Soria, Spain), described provisionally as Leptolophus sp., could be another new Iberian species. The Iberian taxa are characterized by having: more hypsodont, lophodont and heterodont dentition than the Central European Leptolophus taxa (L. stehlini, L. nouleti and L. magnus); thicker styles and stylar ribs in the upper jugal teeth; and thicker coronal cementum. The precocious development of coronal cementum and the high hypsodonty index could be related to different foraging conditions (tougher vegetation, more open or drier habitats with a higher consumption of grit in the diet) inhabited by the Iberian Leptolophus species with respect to their Central European contemporaries.

http://zoobank.org/urn:lsid:zoobank.org:pub:03F87D46-2320-41D2-AE08-333866F005AD

ACKNOWLEDGMENTS

We thank S. Martín de Jesus (Sala de las Tortugas, Universidad de Salamanca), E. Robert (Université Claude Bernard Lyon 1), D. Berthet (Collections of the Musée des Confluences), S. Jiquel, A.-L. Charruault and L. Marivaux (Université de Montpellier) and L. Costeur (Naturhistorisches Museum Basel) for access to comparative specimens. The CT scans were performed at the Universidad de Burgos by R. Porres García. The micro-CT scans were performed at the Microscopy and Microcomputed Tomography Laboratory (CENIEH) with the collaboration of CENIEH staff. We are also grateful to R. Glasgow for editing the English text, H. Astibia for helping us to coat the specimens from Zambrana with ammonium chloride in order to obtain better photographs, M. Rodríguez-Almagro for technical assistance with some of the figures, J.A. Remy for the photographs of Plagiolophus huerzeleri, and two anonymous referees and the JVP’s editor Matthew Borths for helpful comments that have improved the quality of this manuscript. Financial support was provided by the Spanish Ministry of Science and Innovation, The European Regional Development Fund (CGL2017-85038-P and PGC2018-093925-B-C33) and the Basque Country Government (the Research Groups of the Gobierno Vasco/Eusko Jaurlaritza IT1004-16 and IT418-19) and the UPV/EHU projects (PPG17/04). AGO was supported by a Ramón y Cajal fellowship (RYC-2017-22558). LPG received a pre-doctoral grant from the UPV/EHU (PIF16/190).