Claudiosaurus

Claudiosaurus ("claud" is Latin for "lameness" and "saurus" means "lizard") is an extinct genus of diapsid reptiles from the Permian Sakamena Formation of the Morondava Basin, Madagascar. "Claudiosaurus" is the most basal neodiapsid. "Claudiosarus" are found to be a sister group of the Neodiapsida. The pattern of the vertebrate, girle, and limbs indicates that "Claudiosaurus" and "Thadeosaurus" share a common ancestor.
History and discovery.
"Claudiosaurus" is known from the Sakamena Formation of Madagascar. Originally claudiosaurs were found from the Late Permian, but they have been recently also found in Early Triassic deposits of Madagascar.
Biology and description.
"Claudiosaurus" was one of the first members of the Neodiapsida, a group of reptiles containing diapsids more derived than the primitive Araeoscelidia. It had a relatively long body and neck, reaching on overall length of about . It is presumed to have been partially oceanic, living its life in a way similar to the modern marine iguana. The main reason for this theory is that the skeleton included substantial amounts cartilage, instead of bone, indicating it had trouble supporting its weight on land. In particular, the sternum was poorly developed, which would have made walking difficult out of water. Instead, it probably swam by undulating its body and tail, and holding its legs close to the body to increase streamlining. A more recent study however indicates that its vertebral column tail and leg proportions are closer to those of terrestrial reptiles, though it is noted that marine iguanas similarly only differ from terrestrial counterparts very subtly. The mean vertebral is approximately twice of "Hovasaurus". "Claudiosaurus" have a more slender tail than "Hovasaurus". The frontal contributes the dorsal orbital margin. This prevents the prefrontal from contacting the post frontal. The post frontal is ventrally expanded posteriorly and contributes to the orbital rim. The anterior process of the pterygoid is straight. The closest skull comparison can be with the genus "Anarosaurus". "Claudiosaurus" differs from "Acerosodontosaurus" and "Hovasaurus" in the presence of a proportionately long neck.
Behavior.
Locomotion.
It is theorized that "Claudiosaurus" was semi-aquatic. The discovery of pachyostotic thickening of the limb bones and vertebrae supports this theory. The margins of contact in the carpals are poorly defined and therefore retained a lot of cartilage, providing a greater ‘ degree of flexibility’ that would be beneficial for swimming. 
Feeding ecology.
There is evidence of aquatic feeding habits. Supporting this is the small size of the skull, nature of the palate and marginal dentition and the long neck.
Classification.
"Claudiosaurus" is recovered as a relative of turtles by Li et al. (2018), forming a clade with the basal neodiapsid "Acerosodontosaurus".
Further reading.
Caldwell, M. (1995). Developmental Constraints and Limb Evolution in Permian and Extant Lepidosauromorph Diapsids. Journal of Vertebrate Paleontology, 14(4), 459-471. Retrieved February 5, 2020, from www.jstor.org/stable/4523588