Vallesaurus is an extinct genus of Late Triassic elyurosaur drepanosauromorph. First found in Northern Italy in 1975, it is one of the most primitive drepanosaurs. V. cenenis is the type species, named in 2006. A second species, V. zorzinensis, was named in 2010.

 Vallesaurus is a small drepanosaurid about 15 centimetres (5.9 in) long. It is pentadactyl, with the 4th digit being longest and equal in length to the humerus. Its tarsus has a centrale, or an ankle bone which articulates with the tibia. In addition, Vallesaurus also has modified distal tarsals and metatarsals, and a clawless hallux.

 Vallesaurus differs in some characteristics from another drepanosaur, Megalancosaurus. Vallesaurus has a proportionally shorter and higher snout, a thicker and larger maxilla and set of maxillary teeth, and a shorter cervical vertebra. It also lacks the fusion between the neural spines of the second and third dorsal vertebrae. Vallesaurus differs from Drepanosaurus, another drepanosaur, in that it lacks the enormous claw found on the second digit of the manus. It can be distinguished from Drepanosaurus, Megalancosaurus and possibly Dolabrosaurus in the lack of a terminal spine at the end of the tail. In addition, Vallesaurus also differs from Hypuronector, a related drepanosaur, in having anteroposteriorly extended neural spines of the anterior dorsal vertebrae and forelimbs much shorter than the hindlimbs.

 Vallesaurus shares with all other known drepanosaurids a body structure that indicates a specialized adaptation toward climbing, especially on narrow supports such as the twigs of trees. The manus of Vallesaurus has no opposable fingers; however, the shape and length of the fingers suggest good climbing abilities.

 Vallesaurus as well as other drepanosaurids possess a fussed-like structure in the anterior dorsal region and highly modified cervical vertebrae with adaptations that limited lateral mobility. Both structures indicate the presence of powerful muscles and ligaments for the extension of the neck. This possibly suggests a projectile feeding adaptation. The head was suddenly launched forward to catch prey and the limited lateral mobility prevented undesired jerks of the neck which could have dislocated the cervical vertebrae during the quick extension. In smaller drepanosaurids like Megalancosaurus and Vallesaurus, such adaptations may be related to an insectivorous diet. The teeth of Vallesaurus seem well suited to cut or crush the tough exoskeleton of insects and other arthropods.

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Tags: Вымершие рептилии, Триас, авицефалы, диапсиды, дрепанозавроморфы

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