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The skeletal anatomy of the triassic protorosaur Dinocephalosaurus orientalis, from the Middle Triassic of Guizhou province, southern China
The first protorosaur from the Middle Triassic of China, Dinocephalosaurus orientalis Li is known from two specimens: the holotype (an isolated skull in association with the first three cervical vertebrae), and a referred specimen (an almost complete, associated and partially articulated specimen lacking the tail). This material is here described in detail. A complete and amended diagnosis is given for the genus and its only known species. Among protorosaurs, Dinocephalosaurus is the taxon exhibiting the greatest degree of skeletal paedomorphosis, indicating fully aquatic habits.
Dinocephalosaurus orientalis is currently known from two specimens. The holotype (Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, IVPP V13767) comprises the nearly three-dimensionally preserved skull and the first three cervical vertebrae. The second specimen (IVPP V13898) represents a nearly complete, but partially disarticulated, skeleton (the tail is missing). The skull is strongly dorsoventrally compressed and exposed in ventral view only.
The skull of the holotype of Dinocephalosaurus orientalis Li (IVPP V 13767) in right dorsolateral view. The referred specimen of Dinocephalosaurus orientalis Li (IVPP V13898), interpretative drawing of the specimen.