The middle Eocene podocnemidid turtles from the eastern Duero Basin (Soria Province, central Spain)

Abstract Several relatively complete and well-preserved shells of podocnemidid turtles from the Bartonian (late middle Eocene) fossil site of La Solana (Mazaterón locality, Soria province, central Spain), as well as other partial shell remains and isolated plates from the same locality, are analyzed here. Until now, no pleurodiran remains from La Solana or from any other outcrop in the eastern Duero Basin have been formally described. By contrast, fossils of this lineage have been recognized to be very abundant in the western region of this basin, and had been subjected to relatively numerous, detailed studies for more than five decades. Notable faunal differences were identified between the two regions of this basin, both for the turtle fauna and that of other vertebrate lineages, reptiles and mammals. The pleurodiran material identified at La Solana is attributable to Neochelys , a common and diverse genus of freshwater turtles exclusive to the Eocene of Europe. Although several species are currently recognized as valid based on the fossil record of several European countries (most of them exclusively through shell remains, with only one or a few shells being recognized for several of its representatives), the best preserved are those from the western Duero Basin. Intraspecific variability was identified for several characters in the shell of the representative of Neochelys from La Solana. The combination of characters observed in the La Solana material is not compatible with any of the species defined from the western sector of the Duero Basin. The comparative study carried out here shows that it varies systematically from other named species of Neochelys .