The name Thalassochelydia is here referred to the clade that includes all turtles more closely related to Eurysternum wagleri Meyer, 1839c, Plesiochelys etalloni (Pictet and Humbert, 1857), and Thalassemys hugii Rütimeyer, 1873a, than to Pelomedusa subrufa (Bonnaterre, 1789), Testudo graeca Linnaeus, 1758, or Protostega gigas (Cope, 1871). Eucryptodiran turtles from the Late Jurassic of Europe were traditionally classified in several families, in particular Eurysternidae, Plesiochelyidae, and Thalassemydidae, but we are unaware of any higher level name having been pro- posed to unite all into a group. We here recognize that some information is available that hints at the monophyly of these turtles and we therefore here propose a new name for that group, Thalassochelydia, in allusion to their predominantly marine habitat preferences. Increased taxon sampling and the development of new cranial characters recently allowed this group to be supported in a phylogenetic context (Anquetin et al. 2015). In order to avoid potential conflict with the phylogenetic definition of Protostegidae Cope, 1872, as recently proposed by Cadena and Parham (2015), our definition of Thalassochelydia specifically excludes the species Protostega gigas (Cope, 1871).
Full reference: J. Anquetin, C. Puntener, and W. G. Joyce. 2017. A Review of the Fossil Record of Turtles of the Clade Thalassochelydia. Bulletin of the Peabody Museum of Natural History 58(3):317-369
Sister taxa: Amphichelydia, Apertotemporalis, Apholidemys, Asturichelys, Athecae, Casichelydia, Chelone obovata, Chelone sopita, Cryptodira, Cryptrodiramorpha, Euclastochelys, Euclastochelys interrupta, Haichemydidae, Larachelus, Meiolania damelipi, Pancryptodira, Panpleurodira, Paracryptodira, Platychelone, Platychelone emarginata, Plesiochelydiae, Pleurodira, Podocnemis lata, Proganochelydia, Senonemys suemegensis, Sokotochelys, Tacuarembemys, Temnoclemmys cordiformis, Thecophora, Trionychidae, Trionyx fuchienensis, Trionyx tshelkarensis, Protemys, Oligochelone, Chelycarapookidae, Padiochelys, Chelonoides, Pachychelys, Chelonipus, Tomochelone, Yaxartemys, Glaucochelone, Halmyrachelidae, Pseudosphargis, Chelonichnium, Metachelydia, Marina, Terrestria, Cryptodiramorpha, Paludinosa, Fluvialia
• Miocene of Spain (1 collection)
• Jurassic to Cretaceous of France (2)
Total: 95 collections including 158 occurrences