Weigeltisaurid

Description

Weigeltisaurid skulls range from around 3.4–3.7 centimetres (1.3–1.5 in) long in Coelurosauravus to 6 centimetres (2.4 in) in length in Weigeltisaurus. Coelurosauravus had a combined head and trunk length (snout-vent length) of around 18 centimetres (7.1 in) and a total length of at least 32 centimetres (13 in) including the tail. The skulls and jaws of weigeltisaurids are ornamented with horns and tubercles, including chameleon-like frills. The torso and limbs are slender. The skeletons of weigeltisaurds are lightened by large air spaces (skeletal pneumaticity) within the bones. The phalanges of the hands and feet are elongate contrasting strongly with those of most other primitive diapsids, but are similar to those of modern arboreal (tree-climbing) lizards. Unique to weigeltisaurids, the group possesses between 25 and 30 pairs of long, hollow rod-like bones, which project from the lower abdomen dubbed "patagials" These patagial bones, which appear to be novel (neomorphic) bones not found in any other reptile group, have a 1 to 1 correspondence with the gastralia (elongate, thin, crescent-shaped bones found in the lower belly) and appear to articulate with the lateral (outer) gastralia elements. In life, these patagials are thought to have been embedded in a membrane, which connected them, forming a foldable wing. This differs from the situation in living gliding lizards, and the fossil gliding reptiles Xianglong, Mecistotrachelos and kuehneosaurids, where elongated ribs instead fulfill this role. These wings had a wingspan of around 35 centimetres (14 in) in Coelurosauravus.