Jesairosaurus was originally considered a prolacertiform
Sure it has a long neck, but in phylogenetic analysis, it doesn’t nest with Prolacerta or Marlerisaurus, but after the basal lepidosaur Huehuecuetzpalli (described a year later) and prior to other long-necked taxa, including langobardisaurs and drepanosaurs. Note the dorsal nares and large orbit. There’s a very tall scapula here, a precursor to the tall stem in drepanosaurs. The specimen is broken up, but appears to have a tiny antorbital fenestra, a trait that has been argued about in drepanosaurs.
Distinct from most lepidosaurs,
Jesairosaurus has fairly large thecodont teeth, a trait retained by all successors, including tanystropheids and pterosaurs. Gastralia appear here for the first time in this lineage, lost in drepanosaurs, kept in langobardisaurs. The ventral pelvis isn’t fused, but the thyroid fenestra is gone.
Like most lepidosaurs,
the scapulocoracoid was fenestrated. And there’s a nice ossified sternum there.
Folks, not adding this taxon to phylogenetic analyses focused on any of the taxa mentioned above is big mistake. It’s time to clear out all the enigma taxa and nest theme where they belong.
On a side note…
As you know, I’m always attempting to improve the data here. Several months ago I mentioned to a detractor that most prior workers reported forelimbs present in Sharovipteryx. Only Unwin et al. (2000) thought they were buried in the matrix. My detractor claimed the opposite, that I was the only one to see forelimbs. No word yet on this issue. Still waiting.
Another detractor claimed I had seen soft tissue on a Bavarian museum fossil pterosaur. When I asked which specimen, he refused to provide the number.
In a third case I asked to see a closeup of a pterosaur mandible tip that had been published. I wondered if the sharp tip might be a tooth, as it is in other sharp mandible pterosaurs. The offer was refused with the phrase, “trust us, it’s not there.” I replied “trust” is antithetical to Science. No reply and no closeup yet.
So, is it so hard to provide a museum number? A closeup of a photograph? Or a reply to a note on forelimbs? Should we trust other scientists? Or should we test and confirm or refute? There may be cooperation among other paleontologists. Or maybe they’re all very protective of their data. Evidently I also have a very bad reputation, and that may be the reason for the lack of cooperation. These things happen when paradigms are broken.
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.
Unwin DM, Alifanov VR and Benton MJ 2000. Enigmatic small reptiles from the Middle-Late Triassic of Kyrgyzstan. In: Benton M.J., Shishkin M.A. & Unwin D.M. (Eds) The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge U. Press: 177-186.