Earlier we looked at the origin of rhynchosaurs. Today, another look.
This post was inspired
by learning that Kaikaifilusaurus was conspecific with Priosphenodon (Fig. 1). I was also reviewing the Gauthier et al. (1988) of archosaur traits not shared by lepidosaurs, including the postnarial connection of the nasal and premaxilla. (BTW, Brachyrhinodon and Pleurosaurus (lower right, fig. 1) has this connection while pterosaurs do not.) Here bone colors help tell the story of rhynchosaur origins better than any 1000 words can. The reappearance of the lacrimal, quadratojugal and socketed teeth are all part of the story. There may also have been a love child produced by the illicit mating of a Priosphenodon with a Mesosuchus. Well, maybe that mystery will be solved when a taxon is found that nests with them.
The reappearance of teeth
on the premaxilla of Mesosuchus documents some sort of legacy genetic code reappearing. So, if this is the case, there was evidently something in the water that permitted the reappearance of several other previously lost traits.
The infilling of the squamosal
on Priosphendon is also an autapomorphy not shared with other rhynchocephalians.
You can look from here to there,
but you won’t find a closer sister taxa among the archosauromorpha that nests more parsimoniously with rhynchosaurs than the rhynchocephalians. If you do, please let me know. In the meantime, the most comprehensive family tree on this subject can be found here.
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