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Hylaeochelys belli

Reptilia

Taxonomy

Chelone belli was named by Mantell (1844). Its type specimen is BMNH 36529, a partial shell (a distal fragment of costal plate), and it is a 3D body fossil. Its type locality is Tilgate Forest, Cuckfield, which is in a Valanginian terrestrial sandstone in the Tunbridge Wells Sand Formation of the United Kingdom.

It was recombined as Hylaeochelys belli by Lydekker (1889), Delair (1958), Heinrich (1991), Milner (2011), Pérez-García (2012), Pérez-García and Murelaga (2013), Pérez-García and Ortega (2014), Allain et al. (2022).

Synonyms

Platemys mantelli was named by Owen (1841). Its type specimen is BMNH 2288, a partial shell (right hyoplastral), and it is a 3D body fossil. Its type locality is Tilgate Forest, Cuckfield, which is in a Valanginian terrestrial sandstone in the Tunbridge Wells Sand Formation of the United Kingdom.

It was recombined as Plesiochelys mantelli by Lydekker and Boulenger (1887); it was synonymized subjectively with Hylaeochelys belli by Delair (1958), Heinrich (1991), Milner (2011), Pérez-García (2012).
Platemys dixoni was named by Owen (1853). Its type specimen is BMNH 2268, a partial shell (left hyoplastral), and it is a 3D body fossil. Its type locality is Tilgate Forest, Cuckfield, which is in a Valanginian terrestrial sandstone in the Tunbridge Wells Sand Formation of the United Kingdom.

It was synonymized subjectively with Hylaeochelys belli by Delair (1958), Heinrich (1991), Milner (2011), Pérez-García (2012), Pérez-García and Ortega (2014).
Hylaeochelys sollasi was named by Nopcsa (1928). Its type specimen is OUM J.13796, a shell (a carapace in external aspect), and it is a 3D body fossil.

It was synonymized subjectively with Hylaeochelys latiscutata by Milner (2004); it was synonymized subjectively with Hylaeochelys belli by Pérez-García (2012).
Archaeochelys valdensis was named by Lydekker (1889). It is not extant. Its type specimen is BMNH 3532, a partial shell (partial left hyoplastral). Its type locality is Tilgate Forest, Cuckfield, which is in a Valanginian terrestrial sandstone in the Tunbridge Wells Sand Formation of the United Kingdom. It is the type species of Archaeochelys.

It was synonymized subjectively with Hylaeochelys belli by Milner (2011).

Synonymy list

Year	Name and author
1841	Platemys mantelli Owen p. 167
1842	Platemys mantelli Owen p. 167
1844	Chelone belli Mantell
1853	Platemys mantelli Owen p. 11 figs. plate 9, fig. 1
1853	Platemys dixoni Owen p. 12
1887	Plesiochelys mantelli Lydekker and Boulenger p. 272
1889	Archaeochelys valdensis Lydekker pp. 219-220 fig. 50
1889	Hylaeochelys belli Lydekker p. 514
1928	Hylaeochelys sollasi Nopcsa p. 50 fig. 9
1958	Hylaeochelys belli Delair p. 53
1958	Hylaeochelys sollasi Delair p. 53
1991	Hylaeochelys belli Heinrich p. 190
2011	Hylaeochelys belli Milner pp. 301-302 figs. 23.3D, 23.4A
2012	Hylaeochelys belli Pérez-García p. 73 figs. 5-6
2013	Hylaeochelys belli Pérez-García and Murelaga
2014	Hylaeochelys belli Pérez-García and Ortega
2022	Hylaeochelys belli Allain 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)
—	Thalassochelydia
genus	Hylaeochelys
species	belli	(Mantell 1844)

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.

†Hylaeochelys belli Mantell 1844

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Invalid names: Archaeochelys valdensis Lydekker 1889 [synonym], Hylaeochelys sollasi Nopcsa 1928 [synonym], Platemys dixoni Owen 1853 [synonym], Platemys mantelli Owen 1841 [synonym]

Diagnosis

Reference	Diagnosis
A. Pérez-García 2012	Pancryptodiran turtle sharing the following character combination: roughly circular, low shell; wide, shallow notch restricted to the anterior margin of the nuchal plate; shell surface nearly smooth or fluted; lateral margins of the nuchal tend to converge towards the anterior region except in the anteriormost area, where they diverge; continuous or discontinuous neural series consisting of 7e9 plates, the anterior ones very elongated; first neural rectangular, the following plates hexagonal, and the last neural or pair of neurals subpentagonal to subcircular; presence or absence of medial contact of the eighth pairs of costals; two suprapygals, the anterior being longer and the posterior wider; first costal more than twice as wide as long; 11 pairs of peripherals; posterior peripherals longer than those of the anterior; absence of dorsal thickening of the lateral edges in the anterior peripherals; medio-laterally expanded posterior peripherals; single, very short and wide cervical scute; vertebral scutes at least twice as wide as they are long and over half the width of the carapace; first vertebral rectangular, considerably wider than the nuchal, similar in width to that of the fifth vertebral, considerably wider than the second suprapygal; second to fourth vertebrals similar in width, considerably wider than the first and last vertebrals; narrow pleural scutes, extending over one-third of the peripheral plates; contact of the last pair of marginals and the second suprapygal absent; absence of costal-peripheral and bridge fontanelles, but presence of a central plastral fontanelle in some adult specimens, of variable size; partially osseous connection between plastron and peripherals; broad plastral lobes, with the anterior rounded, and the distal region of the posterior one sub-perpendicular to the axial axis, lacking anal notch; entoplastron longer than wide, with scant longitudinal development between the epiplastra; hyoplastra longer than hypoplastra; absence of mesoplastra; postero-lateral expansion of the hypoplastra; straight to markedly sinuous medial sulcus of the plastron; presence of one pair of gular scutes, similar in size to extragulars; gulars not superimposed on the entoplastron; humeral-pectoral grooves situated far behind the posterior margin on the entoplastron; five inframarginals; anal scutes not contacting the hypoplastra.