Re: [dinosaur] Pterosaur origin clues found in lagerpetid archosaurs

[Tim Williams <tijawi@gmail.com>]

I've thought for a long time that pterosaurs (like birds) have a 'ground-up' origin of flight.ÂThe lagerpetid _Kongonaphon_ ( doi/10.1073/pnas.1916631117) provided additional support for this hypothesis (http://dml.cmnh.org/2020Jul/msg00038.html). Ezcurra et al. provide even further evidence, with firmÂsupportÂfor a Lagerpertidae+Pterosauria clade.ÂÂ

So far, no lagerpetid shows highly elongated forelimbs (although there is lengthening of individual elements). Nor is there any evidence that the forelimbs (or pectoralÂgirdle) were used for aerial locomotion. But, like the pennaraptoran ancestors of birds, lagerpetids "had long legs, a bipedal stance and the ability to run fast" (to quote Padian) - the primitive condition for Pterosauromorpha. So both birds and (before them) pterosaurs are likely to have evolved independently from agile, cursorial terrestrial bipeds. The fact that lagerpetids have relatively short forelimbs (especially compared to pterosaurs) does not contradict a 'ground-up' hypothesis. Lagerpetids were the sister taxon to Pterosauria, not the direct ancestors. Relative forelimb length varies greatly among non-avialan pennaraptorans, and the same was likely true for non-pterosaurianÂpterosauromorphs.

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Saltatorial abilities haveÂbeen proposed for lagerpetids (e.g. Sereno & Arcucci, 1993; J. Vert. Paleontol. 13:385-399), but this is contentious. If true, it wouldÂfit the leaping hypothesis of the origin of flight (J. Exp. Biol. 203: 725-739). Arboreal or scansorial abilities seem highly unlikely for lagerpetids, although Ezcurra et al. hint at the possibility of climbing abilities in lagerpetids by virtue of the strongly recurved manual claws. But, as the authors also state, these could be used in predation, as they are in theropods. There's no reason to assume that basal pterosauromorphsÂ(including lagerpetids) were arboreal,Âor had any aptitude (or reason) to venture into trees.Â

On Thu, Dec 10, 2020 at 3:19 AM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler

bcreisler@gmail.com

A new paper:

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MartÃn D. Ezcurra, Sterling J. Nesbitt, Mario Bronzati, Fabio Marco Dalla Vecchia, Federico L. Agnolin, Roger B. J. Benson, Federico BrissÃn Egli, Sergio F. Cabreira, Serjoscha W. Evers, Adriel R. Gentil, Randall B. Irmis, AgustÃn G. Martinelli, Fernando E. Novas, LÃcio Roberto da Silva, Nathan D. Smith, Michelle R. Stocker, Alan H. Turner & Max C. Langer (2020)
Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria.
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-020-3011-4
https://www.nature.com/articles/s41586-020-3011-4


Pterosaurs were the first vertebrates to evolve powered flight and comprised one of the main evolutionary radiations in terrestrial ecosystems of the Mesozoic era (approximately 252-66 million years ago), but their origin has remained an unresolved enigma in palaeontology since the nineteenth century. These flying reptiles have been hypothesized to be the close relatives of a wide variety of reptilian clades, including dinosaur relatives, and there is still a major morphological gap between those forms and the oldest, unambiguous pterosaurs from the Upper Triassic series. Here, using recent discoveries of well-preserved cranial remains, microcomputed tomography scans of fragile skull bones (jaws, skull roofs and braincases) and reliably associated postcrania, we demonstrate that lagerpetids--a group of cursorial, non-volant dinosaur precursors--are the sister group of pterosaurs, sharing numerous synapomorphies across the entire skeleton. This finding substantially shortens the temporal and morphological gap between the oldest pterosaurs and their closest relatives and simultaneously strengthens the evidence that pterosaurs belong to the avian line of archosaurs. Neuroanatomical features related to the enhanced sensory abilities of pterosaurs are already present in lagerpetids, which indicates that these features evolved before flight. Our evidence illuminates the first steps of the assembly of the pterosaur body plan, whose conquest of aerial space represents a remarkable morphofunctional innovation in vertebrate evolution.

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News:

Paleontologists find pterosaur precursors that fill a gap in early evolutionary history

https://phys.org/news/2020-12-paleontologists-pterosaur-precursors-gap-early.html

https://news.stonybrook.edu/newsroom/scientists-identify-a-group-of-small-dinosaur-precursors-as-closest-relatives-of-pterosaurs/

https://gizmodo.com/scientists-uncover-the-mysterious-origin-of-pterosaurs-1845841696

https://www.newscientist.com/article/2262116-ancestor-of-pterosaurs-might-have-been-a-tree-climbing-reptile/

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