Updated November 29, 2015 with new data and a new nesting for Jesairosaurus and the drepanosaurs.
The authors of Wikipedia
have no idea what drepanosaurs are other than reptiles. In the large reptile tree drepanosaurs were descended from Jesairosaurus and, more primitively, the basal tritosaur lepidosauriform, Palaegama. Here we’ll start with Palaegama (Fig. 1), the father of all drepanosaurs and kuehneosaurs.
Palaegama is a basal lizard-like lepidosauriform that shared few obvious traits with the highly derived drepanosaurs. It does not take a transitional taxon, like Jesairosaurus (Fig. 1) to make the case for a relationship here because deletion does nothing to tree topology.
Now we narrow our focus
to Jesairosaurus, the father of all drepanosaurs (Fig. 2). Essentially Jesairosaurus was a long torso palaegamid lepidosauriform. The skulls are readily comparable. The limbs are shorter in the derived taxon.
Jesairosaurus lehmani (Jalil 1997) Early to Middle Triassic ~240 mya was originally described as a prolacertiform and thus related to Prolacerta. All shared traits are by convergence here. By virtue of its nesting, Jesairosaurus is also basal to the kuiehneosaurs, like Coelurosauravus (Fig. 3).
With its bigger torso and smaller limbs,
Jesairosaurus was not a speedster. This was the first step in the evolution of the slow-moving, arboreal drepanosaurs. The high scapula of drepanosaurs finds an origin in Jesairosaurus.
It is unfortunate
that the hind feet and tail are not known for Jesairosaurus, because both of these body parts underwent a great transformation in early drepanosaurs.
As in Palaegama, the pelvis of Jesairosaurus was relatively tiny and included an anterior process of the ilium that developed further in drepanosaurs. While Palaegama employed its expanded ilium to sprint, drepanosaurs were not sprinters, but arboreal climbers and clingers, like modern day chamaeleons.
Jalil N-E 1997. A new prolacertiform diapsid from the Triassic of North Africa and the interrelationships of the Prolacertiformes. Journal of Vertebrate Paleontology 17(3), 506-525.