Pterosaurs and turtles?? Say it ain’t so…

Serious topic: done to prove a point.
I have often argued (Peters 2000a, b, 2002, 2007, 2009, 2010, 2011) against the nesting of pterosaurs with archosaurs and archosauromorphs such as Scleromochlus, Lagerpeton, Parasuchus and Proterochampsa (contra Sereno 1991; Bennett 1998; Irmis et al. 2007; Nesbitt et al. 2009; Hone and Benton 2007, 2008; Brusatte et al. 2010; Nesbitt and Hone 2010; Nesbitt 2011 and others). The problem has always been taxon exclusion. If you delete or exclude the real ancestors and sisters of pterosaurs, they’ll nest in the weirdest places. In the following experiments, you’ll see pterosaurs nest almost anywhere except with archosaurs. They’ll even nest with turtles and pachypleurosaurs, rather than associate themselves with archosaurs!

Figure 1. Click to expand. Here's what happens when you exclude fenestrasaurs, squamates and all the other lepidosauromorphs, but leave the turtles, in a study on pterosaur origins. Note: pterosaurs do not nest with archosaurs.

From the large and fully resolved cladistic analysis in which pterosaurs nested with fenestrasaur squamates, I excluded every taxon from the Lepidosauromorpha except two turtles (Odontochelys and Proganochelys) and the pterosaur MPUM 6009 to see what would happen. Click to expand this image:

When Ichthyostega is the outgroup taxon turtles nest with it and pterosaurs nest at the base of the Sauropterygia.

When three specimens of Gephyrostegus form the outgroup, pterosaurs and turtles nest at the base of the Sauropterygia.

When all of the included non-reptiles form the outgroup taxa turtles nest with Eocaecelia while pterosaurs nest at the base of the Sauropterygia.

When no outgroups are employed pterosaurs nest with turtles as an outgroup to the Archosauromorpha. A shift of branches brings the Sauropterygia to the base of the tree.

Given the opportunity, pterosaurs nest with turtles and basal sea reptiles rather than archosaurs and archosauromorphs. Taxon exclusion was responsible for this. So why do paleontologists continue to include pterosaurs in archosaur studies?

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Bennett, SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoological Journal of the Linnean Society 118:261–309.
Brusatte SL , Benton MJ , Desojo JB and Langer MC 2010. The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida), Journal of Systematic Palaeontology, 8:1, 3-47.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Irmis RB, Nesbitt SJ, Padian K, Smith ND, Turner AH, Woody D and Downs A 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317 (5836): 358–361. doi:10.1126/science.1143325. PMID 17641198.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Nesbitt SJ, Irmis RB, Parker WG, Smith ND, Turner AH and Rowe T 2009. Hindlimb osteology and distribution of basal dinosauromorphs from the Late Triassic of North America. Journal of Vertebrate Paleontology 29 (2): 498–516. doi:10.1671/039.029.0218
Nesbitt SJ and Hone DWE 2010.An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233.
Peters D 2000a Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41
Peters D 2000b.A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Peters D 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. Journal of Vertebrate Paleontology 11 (Supplement) Memoire 2: 1–53.

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