Update March 5, 2016 with the addition of the cladogram from the large reptile tree.
Draco (Fig. 1) and Chlamydosaurus (Fig. 2) are particularly interesting
as both share anterior maxillary fangs and an antorbital fenestra between the prefrontal and jugal (rather than between the lacrimal and maxilla as in other taxa with an antorbital fenestra). A long list of shared character traits unites these two still quite different lizards.
is (at this point in the proceedings) a sister to the last common ancestor. But with that parietal crest, it has definitely evolved apart from the above two taxa for a long time.
We’ve seen this before,
where and when some odd little reptiles shared more traits with each other than with any other tested reptiles. Members of the Fenestrasauria (Cosesaurus, Kyrgyzsaurus, Sharovipteryx, Longisquama, and pterosaurs) also include bipeds with dorsal frills. One of them also glided with outstretched ribs and legs, although distinct from Draco. In Sharovipteryx, the hind legs were much longer than the ribs.
We don’t have
close prehistoric relatives for Draco or Chlamydosaurus yet. So at this point the evolution of rib-gliding or frill-spreading is not yet a gradual demonstration. But the other shared traits are, to my knowledge, unique synapomorphies.
I will update the cladogram this weekend.