PBDB Taxon

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Plesiochelys

Reptilia - Plesiochelyidae

Taxonomy

Plesiochelys was named by Rütimeyer (1873) [Sepkoski's age data: J Kimm Sepkoski's reference number: 1066]. Its type is Plesiochelys solodurensis.

It was assigned to Chelyidae by Portis (1878); to Chelonia by Sepkoski (2002); to Plesiochelydiae by Milner (2004); to Xinjiangchelyidae by Matzke et al. (2004); to Pancryptodira by Danilov and Parham (2008); to Testudines by Anquetin et al. (2009); to Testudines by Pérez-García and Murelaga (2013); to Testudinata by Perea et al. (2014); to Eucryptodira by Joyce (2007), Mateus et al. (2009) and Puntener et al. (2014); and to Plesiochelyidae by Lydekker (1889), Hay (1902), Delair (1958), Yeh (1963), Bräm (1965), Gaffney (1975), Weems (1988), Carroll (1988), Lapparent de Broin et al. (1996), Pérez-García et al. (2008), Anquetin (2012), Anquetin et al. (2014), Anquetin et al. (2014), Anquetin et al. (2015), Anquetin and Chapman (2016), Anquetin et al. (2017), Puntener et al. (2017) and Pérez-Garcia and Ortega (2021).

Species

Clemmys grayi, Emys hugi, Emys hugii, Emys jurensis, Emys trionychoides, P. bigleri, P. etalloni (syn. P. sanctaeverenae, Stylemys lindensis, P. langii, P. solodurensis, P. sanctaverenae, Stylemys hannoverana), P. kwanganensis, P. minor, P. normandicus, P. oshanensis, P. planiceps

Synonyms

Stegochelys was named by Lydekker (1889).

It was synonymized subjectively with Plesiochelys by Gaffney (1975).

It was assigned to Acichelyidae by Delair (1958).
Plesiochelys minor was named by Portis (1878). Its type specimen is GZG 769-7 (syntype), a partial shell (a small hyo- and hypoplas- tron, probably of two distinct specimens (Portis 1878, pl. 16.8); GZG 769-8 (syntype), a small hypoplastron (Portis 1878, not figured), and it is a 3D body fossil. Its type locality is Tönjesbergs, near Hannover, which is in a Kimmeridgian marine horizon in Germany.

It was considered a nomen dubium by Anquetin et al. (2017).
Emys hugi was named by Gray (1831). It is not extant. Its type specimen is NMS 8693 (lectotype; formerly NMS 59), a dis- torted, near-complete shell, a shell. Its type locality is Limestone quarry within or around Solothurn, which is in a Kimmeridgian shallow subtidal limestone in the Reuchenette Formation of Switzerland.

It was replaced with Clemmys grayi by Fitzinger (1835); it was considered a nomen oblitum by Anquetin et al. (2017).
Emys hugii was named by Gray (1831). Its type specimen is unknown, a partial shell (A lateral fragment of carapace (holotype; Cuvier 1824, pl. 15.6), whereabouts uncertain), and it is a 3D body fossil. Its type locality is Limestone quarry within or around Solothurn, which is in a Kimmeridgian shallow subtidal limestone in the Reuchenette Formation of Switzerland.

It was considered a nomen oblitum by Anquetin et al. (2017).
Emys trionychoides was named by Gray (1831). Its type specimen is NMS 8547 (holotype; formerly NMS 61), a partial shell (a fragment of the pygal region of a carapace in visceral view), and it is a 3D body fossil. Its type locality is Limestone quarry within or around Solothurn, which is in a Kimmeridgian shallow subtidal limestone in the Reuchenette Formation of Switzerland.

It was considered a nomen oblitum by Anquetin et al. (2017).
Emys jurensis was named by Keferstein (1834). Its type specimen is NMS 8693 (lectotype; formerly NMS 59), a partial shell, and it is a 3D body fossil. Its type locality is Limestone quarry within or around Solothurn, which is in a Kimmeridgian shallow subtidal limestone in the Reuchenette Formation of Switzerland.

It was considered a nomen oblitum by Anquetin et al. (2017).
Clemmys grayi was named by Fitzinger (1835).

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

Synonymy list

Year	Name and author
1831	Emys hugi Gray
1831	Emys hugii Gray
1831	Emys trionychoides Gray
1831	Emys hugi Gray p. 33
1831	Emys hugii Gray p. 33
1831	Emys trionychoides Gray p. 33
1834	Emys jurensis Keferstein
1835	Clemmys grayi Fitzinger
1873	Plesiochelys Rütimeyer p. 48
1878	Plesiochelys minor Portis p. 12 figs. Plate 2, fig. 8
1878	Plesiochelys Portis p. 18
1889	Plesiochelys Lydekker
1889	Stegochelys Lydekker p. 229
1902	Plesiochelys Hay p. 439
1958	Plesiochelys Delair p. 51
1958	Stegochelys Delair p. 55
1963	Plesiochelys Yeh
1965	Plesiochelys Bräm p. 29
1975	Plesiochelys Gaffney pp. 5-6
1988	Plesiochelys Carroll
1988	Plesiochelys Weems p. 141 figs. Table 2
1996	Plesiochelys Lapparent de Broin et al. p. 557
2002	Plesiochelys Sepkoski
2004	Plesiochelys Matzke et al. pp. 1294-1295
2004	Plesiochelys Milner p. 1460
2007	Plesiochelys Joyce
2008	Plesiochelys Danilov and Parham
2008	Plesiochelys Pérez-García et al.
2009	Plesiochelys Anquetin et al.
2009	Plesiochelys Mateus et al.
2012	Plesiochelys Anquetin p. 28 fig. 10
2013	Plesiochelys Pérez-García and Murelaga
2014	Plesiochelys Anquetin et al.
2014	Plesiochelys Anquetin et al.
2014	Plesiochelys Perea et al.
2014	Plesiochelys Puntener et al.
2015	Plesiochelys Anquetin et al.
2016	Plesiochelys Anquetin and Chapman
2017	Plesiochelys Anquetin et al.
2017	Plesiochelys Puntener et al.
2021	Plesiochelys Pérez-Garcia and Ortega

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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)
—	Thalassochelydia
family	Plesiochelyidae	Rütimeyer 1873
genus	Plesiochelys

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.

G. †Plesiochelys Rütimeyer 1873

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†Plesiochelys bigleri Puntener et al. 2017

†Plesiochelys etalloni Pictet and Humbert 1857

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Invalid names: Plesiochelys langii Rütimeyer 1873 [synonym], Plesiochelys sanctaeverenae Rütimeyer 1873 [synonym], Plesiochelys solodurensis Rütimeyer 1873 [synonym], Stylemys hannoverana Maack 1869 [synonym]

†Plesiochelys kwanganensis Yeh 1963

†Plesiochelys normandicus Bergounioux 1937

†Plesiochelys oshanensis Yeh 1973

†Plesiochelys planiceps Owen 1842

Invalid names: Clemmys grayi Fitzinger 1835 [nomen oblitum], Emys hugi Gray 1831 [nomen oblitum], Emys hugii Gray 1831 [nomen oblitum], Emys jurensis Keferstein 1834 [nomen oblitum], Emys trionychoides Gray 1831 [nomen oblitum], Plesiochelys minor Portis 1878 [nomen dubium], Stegochelys Lydekker 1889 [synonym]

Diagnosis

Reference	Diagnosis
E. S. Gaffney 1975	Member of the Plesiochelyidae (sensu Gaffney, present paper) known from skull, shell, and appendicular elements; foramen palatinum posterius open posteroventrally due to absence of medial process of jugal, anteroposterior length of premaxillae shorter than in Portlandemys, angle between labial ridges (of maxillae and lower jaws) more obtuse than in Portlandemys, median channel between lingual ridges of palate wider in comparison with Portlandemys; length of lower jaw symphysis shorter than in Portlandemys, symphyseal hook absent; prootic process extending anteroventrally to meet expanded processus clinoideus. Carapace oval, nuchal bone indented anteriorly, pygal bone without posterior indentation seen in Eurysternum, two suprapygal bones and six to eight neural bones present; pair of small accessory scutes usually lateral to nuchal (cervical) scute, vertebral scutes wider than in Tropidemys, supramarginal scutes absent. Plastron with or without one or two median fontanelles, mesoplastral bones absent; paired intergular scutes usually extending onto entoplastron, completely separating gular scutes and sometimes partially separating humeral scutes; four or five inframarginal scutes present. Dorsal surface of xiphiplastron with facet for seemingly movable articulation with pubis, sutural attachment between shell and pelvis absent; scapula with neck and coracoid moderately enlarged as in other chelonioids, angle between head and shaft of humerus 117-128 degrees (Bram, 1965).
J. Anquetin et al. 2017	Plesiochelys can be diagnosed as a “plesiochelyid” by the full list of characters provided above for that group. Based on cranial anatomy, Plesiochelys is currently differentiated from Portlandemys by a proportionally broader skull, a more obtuse angle between the labial ridges of maxilla and dentary, placement of the foramina anterius canalis carotici cerebralis closer to the level of the dorsum sellae, and a shorter mandibular symphysis. Based on shell anatomy, Plesiochelys is currently differentiated from Craspedochelys by a more elongated and oval carapace, a deeper nuchal notch, a lower length/width ratio of the costal bones (3.1–3.6, as opposed to 4.3–4.8 or more for costal IV), a relatively long plastron (about 85% to 90% of the carapace length), and a hyoplastron longer than wide and from Tropidemys by the absence of a neural keel, elongated neural bones, and wider vertebral scutes.