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Reptilia - Testudines - Plesiochelyidae

Synonymy list
YearName and author
1869Stylemys lindenensis Maack
1869Stylemys lindensis Maack p. 320
1872Emys dutertrei Sauvage
1873Plesiochelyidae Rütimeyer
1873Plesiochelys dutertrei Sauvage p. 369
1889Plesiochelyidae Lydekker p. 183
1902Plesiochelyidae Hay p. 439
1958Plesiochelyidae Delair p. 51
1966Plesiochelyidae Kuhn p. 22
1975Plesiochelyidae Gaffney pp. 4-5
1988Plesiochelyidae Carroll
1988Plesiochelyidae Weems p. 141 figs. Table 2
1993Plesiochelyidae de Broin and de la Fuente p. 13
1999Plesiochelyidae Goodwin et al. p. 734
2004Plesiochelyidae Milner p. 1460
2011Hispaniachelys Slater et al.
2011Hispaniachelys prebetica Slater et al. p. 1394 fig. 2
2014Plesiochelyidae Anquetin et al.
2016Plesiochelyidae Anquetin and Chapman
2017Plesiochelyidae Anquetin et al.
2017Plesiochelyidae Puntener et al.

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phylumChordataHaeckel 1847
subclassDipnotetrapodomorpha(Nelson 2006)
Testudinata(Oppel 1811)
orderTestudinesBatsch 1788
familyPlesiochelyidaeRütimeyer 1873
familyPlesiochelyidaeRütimeyer 1873

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.

E. S. Gaffney 1975Skull roof: Temporal emargination better developed than in most Chelonioidea except Desmatochelys and Corsochelys; parietal, quadratojugal, and squamosal exposed along temporal margin, parietal-squamosal suture absent. Frontal entering orbital margin. Maxilla and quadratojugal not in contact. Parietals small in contrast to Recent Cheloniidae. Postorbital about intermediate in size between Toxochelys and Recent Cheloniidae. Cheek emargination more extensive than in other Chelonioidea. Jugal relatively small in contrast to living Cheloniidae. Nasals present. Prefrontals meeting in midline. Prefrontal-frontal suture transverse. Palate: Primary palate present. High labial ridge and strong lingual ridge directly bordering apertura narium interna. Ventral margin of labial ridge convex in lateral view. Processus pterygoideus externus developed as in most Testudinoidea and not reduced as in Cheloniidae. Foramen palatinum posterius present (but open posterolaterally in Plesiochelys). Foramen praepalatinum present. Vomer completely separating palatines in ventral view but lacking lateral expansion seen in most cryptodires. Basisphenoid and basioccipital of equal width in ventral view. Prominent transverse ridge on posterior surface of processus articularis of quadrate with trough on ventral side. Braincase: Trabeculae of rostrum basisphenoidale not fused or closely apposed. Sella turcica somewhat reduced in comparison with Chelydra but not so reduced as in most other Chelonioidea. Paired foramina anterius canalis carotici interni not lying close together as in Toxochelys or Cheloniidae but not placed far laterally as in Chelydra and most Testudinoidea. Dorsum sellae high and separated from sella turcica and foramina anterius canalis carotici interni by prominent bone surface having sagittal ridge. Posterior portion of sella turcica not concealed by overhanging dorsum sellae. Canalis caroticus internus not entering sulcus cavernosus as in Recent Cheloniidae. Processus inferior parietalis reduced in anteroposterior extent in comparison to Chelydra and Testudinoidea but not so reduced as in Recent Cheloniidae. Foramen nervi trigemini relatively smaller in Chelydra and conspicuously smaller than in Recent Cheloniidae. Processus trochlearis oticum moderately well developed, as in Chelydra. Parietal extending ventrally to meetpterygoid along posterior margin of foramen nervi trigemini, as in many batagurine testudinids. Epipterygoid large and broadly entering margin of foramen interorbitale; entering or not margin of foramen nervi trigemini. Anterior opening of foramen nervi abducentis posteroventral to base of processus clinoideus in contrast to Recent Cheloniidae and most turtles. Lower Jaw: Triturating surface narrow in contrast to Recent Cheloniidae. High labial and subequal or lower (but distinct) lingual ridge; well developed trough between labial and lingual ridges for reception of lingual ridge of skull; no accessory ridges present. Symphyseal hook present or absent. Processus coronoideus higher than in Recent Cheloniidae. Surangular exposed posteriorly in contrast to Chelydra but not so exposed as in Caretta. Surangular bearing variable portion of area articularis mandibularis as in Recent Cheloniidae. Splenial present and large in contrast to nearly all other cryptodires. Fossa meckelii and most of sulcus (canalis) cartilaginis meckelii closed medially by splenial and prearticular.
J. Anquetin et al. 2017“Plesiochelyids” are primarily differentiated from all other thalassochelydians by the presence of a high dorsum sellae that does not overhang the sellae turcica, the placement of the foramina anterius canalis carotici cerebralis more anterior than the level of the dorsum sellae, the exclusion of the epipterygoid from the anterior margin of the foramen nervi trigemini (also in Juras-ichelon oleronensis), a relatively large size (carapace length 400 to 550 mm), the lack of carapacial fontanelles in adults, an osseous bridge, and, at most, a central plastral fontanelle.