page_title: Dinocephalosaurus
section_title: Limbs
hierarchical_section_title: Dinocephalosaurus / Description / Limbs
caption_attribution_description: Dinocephalosaurus orientalis, a protorosaur from the Middle Triassic of China, pencil drawing
context_page_description: Dinocephalosaurus is a genus of long necked, aquatic protorosaur that inhabited the Triassic seas of China. The genus contains the type and only known species, D. orientalis, which was named by Li in 2003. Unlike other long-necked protorosaurs, Dinocephalosaurus convergently evolved a long neck not through elongation of individual cervical vertebrae, but through the addition of cervical vertebrae that each have a moderate length. Like other tanystropheids, however, Dinocephalosaurus probably used its long neck to hunt for prey, utilizing a combination of suction, created by the expansion of the throat, and the fang-like teeth of the jaws to ensnare prey. It was probably a marine animal by necessity, as suggested by the poorly-ossified and paddle-like limbs which would have prevented it from going ashore.
  Specimens belonging to the genus were first discovered in a locality near Xinmin in Guizhou, China in 2002. At the same locality, which dates to 244 million years ago, other marine reptiles such as Mixosaurus, Keichousaurus, and Wumengosaurus have also been found.
context_section_description: Dinocephalosaurus had relatively large legs terminating in flipper-like feet. The forelimbs and hindlimbs are roughly the same length, unlike Tanystropheus where the forelimbs are much smaller. Whereas most protorosaurs, such as Tanystropheus, Macrocnemus, and Langobardisaurus, had relatively ossified limbs adapted for terrestrial life, the stout limbs of Dinocephalosaurus are poorly ossified and resemble those of nothosaurs. Out of the carpal bones, only six are ossified; similarly, only three of the tarsal bones are ossified. Additionally, the astragalus and calcaneum also do not articulate with each other in the ankle, instead forming simple and rounded ossifications.
  These traits are probably neotenic, which similarly characterizes traits found in many other aquatic tetrapods. While Tanystropheus is likely also neotenic, it does not approach Dinocephalosaurus in the extremity of this condition. Several other peculiar traits are present in the feet of Dinocephalosaurus. Unlike Tanystropheus and most other protorosaurs, the fifth metatarsal of Dinocephalosaurus is simple and straight instead of hooked. Tanystropheus merely has a fifth metatarsal which is mildly thickened at the top end, and it additionally possesses a long phalanx on the fifth digit that acts not unlike another metatarsal. On the third digit of the foot, there are four phalanges but none of them appear to be the terminal claw, which suggests that Dinocephalosaurus had a higher-than-average count of at least five phalanges in the third digit.
caption: Restoration
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