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Thalassemydidae

Reptilia - Testudines - Thalassemydidae

Discussion

Under the current state of knowledge, it may appear superfluous to maintain the name Thalassemydidae because it is redundant with Thalassemys at the moment. However, the phylogenetic relationships of Thalassemys spp. with other thalassochelydians have never been properly explored. One of the main reasons for this is the absence of cranial material for thalassemydids. Pending better understanding of thalassochelydian relationships, we maintain the use of the name Thalassemydidae for practical reasons, but, once again highlight its taxonomic ambiguity through the use of quotation marks.

Taxonomy

Thalassemydidae was named by Zittel (1889). It is not extant.

It was assigned to Chelonia by Lortet (1892); to Cryptodira by Hay (1902), Hay (1908); to Thalassemydoidae by Hay (1930); to Cryptodira by Zittel (1890), Kuhn (1946); to Pleurosternoidea by Kuhn (1966); to Eucryptodira by Anquetin et al. (2014); and to Pancryptodira by Puntener et al. (2015).

Subtaxa

Acichelys, Changisaurus, Emys beaugrandi, Pelobatochelys, Phyllemys, Sontiochelys, Trionyx primoevus, Yaxartemys

Synonyms

Emys beaugrandi was named by Sauvage (1872). Its type specimen is MHNB 215 (holotype), a partial shell (a carapace fragment), and it is a 3D body fossil. Its type locality is Moulin-Wibert, which is in a Kimmeridgian marginal marine claystone in France.

It was recombined as Plesiochelys beaugrandi by Sauvage (1873); it was considered a nomen dubium by Anquetin et al. (2017).
Acichelyidae was named by Lydekker (1889).

It was synonymized subjectively with Thalassemydidae by Kuhn (1966).

It was assigned to Cryptodira by Lydekker (1889); to Chelonii by Jaekel (1911); and to Cryptodira by Delair (1958).
Trionyx primoevus was named by Bergounioux (1937). Its type specimen is MHNH uncat. (holotype), a partial shell (poorly preserved plastron), and it is a 3D body fossil. Its type locality is Sainte-Adresse, Cap de La Hève, which is in a Kimmeridgian marine horizon in the Marnes à Deltoideum delta Formation of France.

It was considered a nomen dubium by Anquetin et al. (2017).

Synonymy list

Year	Name and author
1872	Emys beaugrandi Sauvage
1873	Plesiochelys beaugrandi Sauvage p. 367
1889	Acichelyidae Lydekker
1889	Thalassemydidae Zittel
1890	Thalassemydidae Zittel p. 527
1892	Thalassemydidae Lortet p. 24
1902	Thalassemydidae Hay p. 440
1908	Thalassemydidae Hay pp. 126-127
1911	Acichelyidae Jaekel p. 187
1930	Thalassemydidae Hay p. 75
1937	Trionyx primoevus Bergounioux
1946	Thalassemydidae Kuhn p. 58
1958	Acichelyidae Delair p. 54
1966	Thalassemydidae Kuhn p. 22
2014	Thalassemydidae Anquetin et al. p. 19
2015	Thalassemydidae Puntener et al.

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda

Rank	Name	Author
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
—	Sauropsida
class	Reptilia
—	Testudinata	(Oppel 1811)
order	Testudines	Batsch 1788
—	Pancryptodira	Joyce et al. 2004
family	Thalassemydidae	Zittel 1889
family	Thalassemydidae	Zittel 1889

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Fm. †Thalassemydidae Zittel 1889

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G. †Changisaurus Young 1959

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†Changisaurus microrhinus Young 1959

†Changisaurus wutuensis Young 1961

G. †Phyllemys Schmidt 1944

G. †Sontiochelys Stache 1905

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†Sontiochelys cretacea Stache 1905

G. †Yaxartemys Riabinin 1948

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†Yaxartemys longicauda Riabinin 1948

Invalid names: Acichelyidae Lydekker 1889 [synonym], Emys beaugrandi Sauvage 1872 [nomen dubium], Trionyx primoevus Bergounioux 1937 [nomen dubium]

Diagnosis

Reference	Diagnosis
O. P. Hay 1908	Shell more or less incompletely ossified. Usually at least a central plastral fontanel present; often also costo-peripheral vacuities. Plastron loosely connected with the carapace; never closely sutured thereto. Limbs fitted for walking; never developt as flippers. Skull, when known, with the temporal fossae more or less rooft over. Triturating surfaces of the jaws probably always broad. Neck short.