Tritosauria and Shenzhoupterus abstracts

Part 3
The following manuscripts are independently published online without peer-review at the website.

Better to put them out there this way
than to let these works remain suppressed. Hope this helps clarify issues.

Peters D 2018e. A new lepidosaur clade: the Tritosauria
PDF of manuscript and figures

Several lizard-like taxa do not nest well within the Squamata or the Rhynchocephalia. Their anatomical differences separate them from established clades. In similar fashion, macrocnemids and cosesaurids share few traits with putative sisters among the prolacertiformes. Pterosaurs are not at all like traditional archosauriforms. Frustrated with this situation, workers have claimed that pterosaurs appeared without obvious antecedent in the fossil record. All these morphological ‘misfits’ have befuddled researchers seeking to shoehorn them into established clades using traditional restricted datasets. Here a large phylogenetic analysis of 1253 taxa and 231 characters resolves these issues by opening up the possibilities, providing more opportunities for enigma taxa to nest more parsimoniously with similar sisters. Remarkably, all these ‘misfits’ nest together in a newly recovered and previously unrecognized clade of lepidosaurs, the Tritosauria or ‘third lizards,’ between the Rhynchocephalia and the Squamata. Tritosaurs range from small lizard-like forms to giant marine predators and volant monsters. Some tritosaurs were bipeds. Others had chameleon-like appendages. With origins in the Late Permian, the Tritosauria became extinct at the K–T boundary. Overall, the new tree topology sheds light on this clade and several other ‘dark corners’ in the family tree of the Amniota. Now pterosaurs have more than a dozen antecedents in the fossil record documenting a gradual accumulation of pterosaurian traits.

Peters, D. 2018f. New data on Shenzhoupterus chaoyangensis, an unusual Lower Cretaceous pterosaur
PDF of manuscript and figures

A recently described specimen of a new genus of pterosaur from the Lower Cretaceous Jiufotang Formation of northeastern China, Shenzhoupterus chaoyangensis, was assigned to the Chaoyangopteridae within the Azhdarchoidea. Originally the posterior skull was traced as an indistinct sheet with only a drop-shaped orbit piercing it at mid-height. That morphology would be atypical for pterosaurs, but a low orbit is found in azhdarchids. A first-hand observation provided new data. Here a new technique, known as Digital Graphic Segregation (DGS), enabled the identification of every bone in the chaotic jumble of the posterior skull and a new reconstruction of the specimen’s “face” in which the orbit was very high on the skull and otherwise more in accord with other pterosaurs. Other purportedly missing elements including the pelvis, prepubis, pteroid and sternal complex were also identified. A new reconstruction of Shenzhoupterus demonstrates very few synapomorphies with Chaoyangopterus, but several with tapejarids and dsungaripterids.

These manuscripts benefit from
ongoing studies at the large reptile tree (LRT, 1253 taxa) in which taxon exclusion possibilities are minimized and all included taxa can trace their ancestry back to Devonian tetrapods.

1 thought on “Tritosauria and Shenzhoupterus abstracts

  1. Do it TO IT!!!!! YES! I wish I had a fly on the wall with a camera to catch the expressions on your detractors’ faces!!!!

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