Crocodyliformes and Testudines from the Eocene of the Duero Basin (northwestern Spain): an update of their diversity and stratigraphic context

ABSTRACT

The Palaeogene sedimentary successions of the Duero Basin host an important record of fossil vertebrates, especially mammals and reptiles. The main fossil sites are placed at the west margin (Salamanca and Zamora areas) spanning from the Lutetian to the late Priabonian; and at the southeast tip (Almazán Basin) mainly Bartonian in age. The continued study of the sites is supplying new data that will improve the chronostratigraphy and the correlation between the western and eastern regions of the basin. The diversity and phylogenetic relationships of the represented fauna have been revised in recent years with the reassignment of some remains and the diagnosis of some new taxa. Four lineages of turtles are represented: Podocnemididae (Neochelys), Carettochelyidae (Allaeochelys), Trionychidae and Testudinidae (Pelorochelon). Crocodyliform paleobiodiversity is composed of notosuchians (close to Iberosuchus) and, at least, three crocodylian lineages: Planocraniidae (Duerosuchus), Alligatoroidea (Diplocynodon) and Crocodyloidea (‘Asiatosuchus’). The distribution of these taxa is not homogeneous throughout the basin, and a deep transformation is recognised throughout the middle Eocene. The fitting of the distribution and relationships of the reptilian fauna from the Duero Basin provides valuable information to understand some faunistic dynamics such as the endemism process of northwestern Iberia from the middle of the Eocene.

KEYWORDS:

• Palaeogene
• reptiles
• Iberian Peninsula
• chronostratigraphy

Acknowledgments

This manuscript is a contribution to the tribute volume to Prof. Jorge Morales as an expression of our recognition of his legacy to Palaeontology and, in particular, to the knowledge of Iberian Cenozoic mammalian faunas. The authors would also like to pay tribute to the late Emiliano Jiménez Fuentes that passed away while writing this article. Emiliano studied the vertebrate fauna of the Duero Basin, mainly turtles, since his arrival at Salamanca University in the late 1960s. Towards the end of his career, he contributed to current knowledge of the Eocene vertebrates of the Duero Basin, promoting such knowledge through “Sala de las Tortugas”, a Museum at Salamanca University that was his lifeful personal project.

This research has been funded by the Spanish Ministerio de Ciencia e Innovación (PID2019- 397 111488RB-I00) (for FO, AdC, FE, IN, APG, JLS and APG), Ministerio de Ciencia, Innovación y Universidades (PGC2018-094566-B-C21) (for IA and PH), and a Ministerio de Educación fellowship (FPU 2016/01058) (for AdC). Field works were carried out in by the authors in the Duero Basin were founded by the Dirección General de Patrimonio Cultural (Junta de Comunidades de Castilla y León). We want to acknowledge the numerous colleagues involved in both the excavations and in different stages of the activity carried out on the Vertebrate Palaeontology at the Duero Basin at the Colección de Vertebrados Fósiles de la Cuenca del Duero of the Salamanca University. We also thank the editor G. Dyke; the editors of this volume (Daniel DeMiguel, Beatriz Azanza, Alberto Valenciano, Pablo Peláez-Campomanes and Plinio Montoya) for their invitation to be part; and to E Puértolas-Pascual and ÀH Luján for their valuable comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Institutional Abbreviations

IPS, Institut Català de Paleontologia Miquel Crusafont (formerly ‘Institut de Paleontologia de Sabadell’), Barcelona, Spain.; STUS, Colección de Vertebrados Fósiles de la Cuenca del Duero (formerly ‘Sala de las Tortugas’). Universidad de Salamanca, Salamanca, Spain.

Additional information

Funding

This work was supported by the Spanish Ministry of Science and Innovation [PID2019- 397 111488RB-I00]; Spanish Ministry of Science and Innovation [PGC2018-094566-B-C21]; Spanish Ministry of Education [FPU 2016/01058].