Juvenile Rhamphorhynchus and flightless pterosaur abstracts

Part 4
The following manuscripts are independently published online without peer-review at the DavidPetersStudio.com website. http://www.davidpetersstudio.com/papers.htm

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

Peters D 2018g. First flightless pterosaur
PDF of manuscript and figures

Pterosaur fossils have been discovered all over the world, but so far no flightless pterosaurs have been reported. Here an old and rarely studied pterosaur fossil (Sos 2428) in the collection of the Jura Museum in Eichstätt, Germany, was re-examined and found to have a reduced pectoral girdle, small proximal wing elements (humerus, radius and ulna), three vestigial distal wing elements, the relatively longest pelvis of any pterosaur and the widest gastralia, or belly ribs. This discovery represents a unique morphology for pterosaurs. The Jura specimen lacked the wing size, forelimb muscularity and aerodynamic balance necessary to sustain flapping flight. It was a likely herbivore.

Peters D 2018h. First juvenile Rhamphorhynchus recovered by phylogenetic analysis
PDF of manuscript and figures
Standing seven to 44 centimeters in height, a growing list of 120+ specimens assigned to the pterosaur genus Rhamphorhynchus are known chiefly from the Solnhofen Limestone (Late Jurassic, southern Germany). An early study recognized five species and only one juvenile. A later study recognized only one species and more than 100 immature specimens. Phylogenetic analyses were not employed in either study. Workers have avoided adding small Solnhofen pterosaurs to phylogenetic analyses concerned that these morphologically distinct specimens were juveniles that would confound results. Here a large phylogenetic analysis that includes tiny Solnhofen pterosaurs tests that concern and seeks an understanding of relationships and ontogeny within the Pterosauria with a focus on Rhamphorhynchus. 195 pterosaurs were compiled with 185 traits in phylogenetic analysis. Campylognathoides + Nesodactylus were recovered as the proximal outgroups to the 25 Rhamphorhynchus specimens. The ten smallest of these nested at the clade base demonstrating phylogenetic miniaturization. Two Rhamphorhynchus had identical phylogenetic scores, the mid-sized NHMW 1998z0077/0001, and the much larger, BMNH 37002. These scores document a juvenile/adult relationship and demonstrate isometry during pterosaur ontogeny, as in the azhdarchid, Zhejiangopterus, and other pterosaurs. Rather than confounding results, tiny Solnhofen pterosaurs illuminate relationships. All descended from larger long-tailed forms and nested as transitional taxa at the bases of the four clades that produced all of the larger Late Jurassic and Cretaceous pterodactyloids. No long-tailed pterosaurs survived into the Cretaceous, so miniaturization was the key to pterosaur survival beyond the Jurassic.

These manuscripts benefit from
ongoing studies at the large reptile tree (LRT, 1256 taxa) in which taxon exclusion possibilities are minimized and all included taxa can trace their ancestry back to Devonian tetrapods.


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