The oldest evidence of a dortokid turtle, stem Pleurodira, from the uppermost Hauterivian-basal Barremian El Castellar Formation, Teruel, Spain

Abstract

Purpose Dortokidae is a poorly understood group of panpleurodires, exclusive to the European record. Dortokidae is one of the few defined clades of the stem group of Pleurodira, grouping all the forms of this stem described in the postJurassic record of Laurasia. Despite this clade has a relatively wide temporal distribution, only three valid forms of Dortokidae are currently known: one from the late Barremian (Early Cretaceous) of Morella (Spain), Eodortoka morellana; another from the uppermost Cretaceous of Spain and probably southern France, Dortoka vasconica; and the last one from the Paleogene of Romania, Ronella botanica. The oldest of these taxa is synchronous with the findings of Dortokidae indet. from the Spanish fossil locality of Vallipo´n, Vallipo´n and Morella being the only two localities where Lower Cretaceous material of this clade was so far known. Dortokidae is recognized in this paper for the first time in El Castellar Formation, by a partial xiphiplastron. This finding comes from the El Castellar locality (Teruel, Spain). Methods The plate from El Castellar is compared with the xiphiplastra of all so far valid representatives of Dortokidae, and with the indeterminate form from Vallipo´n. A phylogenetic hypothesis on the members of this clade is proposed. Results The specimen studied here is identified as the oldest known evidence of Dortokidae, being recognized as Dortokidae indet. Conclusions This new remain of a dortokid expands the known temporal range of distribution for this clade, being recognized from the uppermost Hauterivian-basal Barremian levels.