Thalassochelydia

Thalassochelydia is a clade of extinct turtles from the Late Jurassic and potentially Early Cretaceous of Europe. The group is defined as including Eurysternum, Plesiochelys and Thalassemys to the exclusion of Pelomedusa, Testudo and Protostega. While a clade uniting the families Eurysternidae, Plesiochelyidae and Thalassemydidae had been supported by phylogenetic evidence, a name was not given for the clade until 2017, when Jérémy Anquetin and colleagues coined Thalassochelydia. While inner relationships of the clade are so uncertain as to make the monophyly of the families questionable, the significant diversity of thalassochelydians makes using the potentially invalid terms useful to describe the different morphologies.[1] The monophyly of Thalassochelydia was further supported by a later analysis by Serjocha Evers and Roger Benson in 2019, where the group, represented by Solnhofia and Plesiochelyidae was sister taxon to Sandownidae within the clade Angolachelonia, which, unlike as found by Anquetin et al. earlier, was outside Cryptodira and Testudines.[2] The phylogeny below of Thalassochelydian inter-relationships follows the results of Anquetin and colleagues in 2017.[1]

Thalassochelydia	"Eurysternidae"   Achelonia     Chelonides     Eurysternum     Hydropelta     Idiochelys     Palaeomedusa     Parachelys     Solnhofia     "Plesiochelyidae"   Craspedochelys     Plesiochelys     Portlandemys     Tropidemys       Enaliochelys     Jurassichelon     Neusticemys     Owadowia     Pelobatochelys   "Thalassemydidae" Thalassemys

Thalassochelydia Temporal range: Late Jurassic, Oxfordian–Tithonian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira
Infraorder:	Eucryptodira
Clade:	†Thalassochelydia Anquetin et al., 2017[1]
Subgroups[1]
Aplax Cyrtura Enaliochelys Euryaspis Hispaniachelys Jurassichelon Neusticemys Owadowia Pelobatochelys Eurysternidae Plesiochelyidae Thalassemydidae

References

1. Anquetin, J.; Püntener, C.; Joyce, W.G. (2017). "A Review of the Fossil Record of Turtles of the Clade Thalassochelydia" (PDF). Bulletin of the Peabody Museum of Natural History. 58 (2): 317–369.
2. Evers, S.W.; Benson, R.B.J. (2018). "A new phylogenetic hypothesis of turtles with implications for the timing and number of evolutionary transitions to marine lifestyles in the group". Palaeontology. 62 (2): 93–134. doi:10.1111/pala.12384.