Oryctos
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Accès privé :
| volume 3, 2000 |
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Haiyan Tong & Eugene S. Gaffney, Description of the skull of Polysternon provinciale (Matheron, 1869), a Side-Necked Turtle (Pelomedusoides : Bothremydidae) from the Late Cretaceous of Villeveyrac, France. Oryctos 3, 9-18.
Polysternon is a European side-necked turtle based only on shell material. A skull found from the Late Cretaceous of Villeveyrac, Herault, France, is referred to this taxon because shells clearly belonging to Polysternon provinciale occur in the same beds. The skull of Polysternon shows that it is a bothremydid with the quadrate-basisphenoid covering the prootic ventrally, the eustachian tube separated from the stapes, precolumellar fossa absent, condylus occipitalis consisting only of exoccipitals and an exoccipital-quadrate contact. Polysternon lies in the Bothremys-Group because it has triangular, expanded triturating surfaces, extensive exposure of the palatine on the triturating surfaces, and a supraoccipital-quadrate contact. Polysternon is most closely related to Foxemys. They possess a number of characters in common including an open incisura columellae auris and a deep pterygoideus muscle concavity. Polysternon differs from Foxemys in having a broader midline, palatal depression, a narrower triturating surface with lower labial ridges, and a condylus occipitalis that is placed farther posterior.
Keywords: pleurodire, Polysternon, bothremydid, Late Cretaceous, France
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