Cranial morphology of the European Jurassic turtles Portlandemys and Plesiochelys. Bulletin of the AMNH ; v. 157, article 6

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New York : American Museum of Natural History
"A theory of relationships is presented in which the Jurassic turtle genera Portlandemys and Plesiochelys are hypothesized as members of the monophyletic group Chelonioidea based on the possession of the following shared derived characters: 1) dorsum sellae high and separated from sella turcica and foramen anterius canalis carotici interni by prominent bone surface that usually has a sagittal ridge, 2) posterior part of sella turcica not concealed by overhanging dorsum sellae. The relationships of these genera within the Chelonioidea are more difficult to test owing to the fact that at present only the Recent forms are cranially as well known as Portlandemys and Plesiochelys. Nonetheless, I have suggested two contradictory hypotheses, one indicating Plesiochelys and Portlandemys as the sister group of the Dermochelyidae plus Cheloniidae, and the other indicating Plesiochelys as the sister group of the Toxochelyidae, Dermochelyidae, and Cheloniidae. The first hypothesis is consistent with derived characters of the palatine artery, whereas the second is consistent with postcranial derived characters"--p. 491.
p. 489-543 : ill. ; 26 cm.
Includes bibliographical references (p. 541-543).