A new latest Cretaceous pleurodiran turtle (Testudinata: Dortokidae) from the Hateg Basin (Romania) documents end-Cretaceous faunal provinciality and selective survival during the K-Pg extinction

Dortokidae is an endemic family of stem-pleurodiran turtles, known exclusively from the Cretaceous and early Paleogene of Europe. Here we describe a new dortokid taxon from the Upper Cretaceous (Maastrichtian) Sinpetru Formation of the southern Hajeg Basin, Romania The type material of Dortoka vremiri sp. nov. comprises a well-preserved carapace and a nearly complete plastron as well as the in situ right scapula and right pubis. Phylogenetic analyses performed to assess the position and interrelationships of Dortoka vremiri sp. nov. within Dortokidae as well as within the wider Pleurodira recovered the new taxon firmly nested within Dortokidae, and together with other dortokids, placed along the stem lineage of pleurodires. Our analysis provides evidence for allopatric speciation in Dortoka through the presence of two distinct lineages - an eastern and a western European lineage, respectively. A similar east/west disjunct distribution pattern has also been established previously for several vertebrate groups such as other turtles, dinosaurs and mammals, probably resulting from isolation due to the particular palaeogeographical setting of the Late Cretaceous European Archipelago. The phylogeny demonstrates local survival of Dortoka across the K-Pg boundary as the sister-taxon of D. vremiri is D. botanica from the uppermost Paleocene deposits of Romania and points to geographical selectivity, as the western lineage of Dortoka went extinct before the Paleogene. Osteology and novel taphonomical data imply a semi-terrestrial lifestyle for Kallokibotion bajazidi, a turtle occurring in coeval faunas with the aquatic and smaller-sized D. vremiri and most likely going extinct at the K-Pg boundary. Altogether, this pattern is consistent with selective extinction of terrestrial taxa previously observed for other continental vertebrate assemblages across the end-Cretaceous mass extinction with only two other examples from turtles.