Taxonomy, systematics, and diversity of the European oldest testudinids

Testudinidae is a clade of tortoises known in Europe from the early Eocene. It is the only lineage of terrestrial turtles identified in the post-Paleocene record of this continent. However, very little information on the taxonomy and systematics of the Eocene representatives is currently available. The oldest testudinids from Europe, recovered in several countries, are studied here. Some of them were previously attributed to genera defined in North America. The hypothesis suggesting that the European Eocene testudinids correspond to genera exclusive to this continent is confirmed here. In this sense, two new genera, Fontainechelon (early Eocene) and Pelorochelon (middle Eocene), are proposed. The largest collection of European Paleogene testudinids, from the middle Eocene of the Spanish site of Mazateron (Soria), is analyzed for the first time. A new species from this locality is defined. The validity of various previously proposed taxa is refuted, and the diagnosis of several forms is emended. Thus, the diversity, taxonomy, phylogenetic relationships, and biogeographical and stratigraphic distributions of the European primitive representatives of this successful extant clade are analyzed.