One core and basis of the Pterosaur Heresies blog is to demonstrate that, how and why pterosaurs have nothing in common with dinosaurs or their precursors, despite reams of traditional literature promoting that relationship. For example:
“Pterosaurs and dinosaurs have been grouped together for along time, and today, the prevalent view among vertebrate paleontologists is still that they do indeed form a natural group of animals.” — Nick Fraser (2006) in “Dawn of the Dinosaurs.”
If this false paradigm continues another two years that will complete a full three decades of belief in the official, “Ornithodira,” the clade THEY say includes both pterosaurs and dinosaurs. I say ‘belief’ because there’s absolutely no evidence for this relationship — as traditional paleontologists themselves have noted (see below).
“Pterosaurs appear suddenly in the fossil record and in full possession of all their highly derived characters…” — David Hone and Michael Benton (2007, 2008).
“As Figure 4.3 illustrates, paleontologists don’t really know where this group should sit within the diapsid family tree. The reason for this is simple — a complete lack of protopterosaurs that might link this group to other diapsids.” — David Unwin in The Pterosaurs from Deep Time.
Unfortunately, such statements give ammunition to Creationists, because it sounds like pterosaurs were “specially created” and nothing could be further from the truth. So this damages the good names of both Paleontology and Science and can only be repaired by professional paleontologists with PhDs. I’ve done and continue doing my part.
To put the final nail in the coffin
No paleontologist has been able to put forth even a short series of taxa that demonstrate a gradual accumulation of pterosaurian traits within the Archosauria or Archosauriformes.
It’s actually THIS EASY to solve the problem:
If you include several hundred representatives from the gamut of prehistoric reptiles in phylogenetic analysis, at least by default and at best by shared homologies, you will recover some taxa that will nest closer to pterosaurs than to other reptiles. So it’s the shame of paleontology that no one else has attempted this time-consuming, but otherwise relatively easy task by expanding the taxon list to include lepidosauromorphs, lizards, tritosaurs and fenestrasaurs. Actually it can be done with as few as a dozen key taxa if you’re pressed for time, as already shown in an academic publication (Peters 2000). The taxa it promotes continue to be ignored by all other workers* in one of the more interesting feuds/wars in the history of paleontology. I don’t care if you ignore the paper. Don’t ignore the taxa.
History of the Ornithodira
In the earliest days of phylogenetic analysis, Gauthier & Padian (1985) placed pterosaurs within the clade Ornithosuchidae (Huene 1914) along with Lagosuchus (= Marasuchus (Sereno & Arcucci 1994)), and the Dinosauria.
Later, Gauthier (1986, Fig. 2) noted that the position of pterosaurs and Marasuchus with respect to dinosaurs was not resolved, but found the three formed a monophyletic group he called the Ornithodira. Sereno (1991) followed and expanded on this by including Scleromochlus.
While reviewing Sereno (1991), Kellner (1996) concluded that no particular character linked pterosaurs to the Archosauria (sensu stricto), but added that because of several shared derived characters with basal dinosauromorphs, the traditional hypothesis was the best supported at the time.
Peters (2000) added several taxa (Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama) that had been excluded in prior studies to three prior phylogenetic analyses and recovered trees in which these taxa nested closer to pterosaurs than any included archosaur. Refinements to the observed morphologies and expansion in the taxon list (both chronicled in PterosaurHeresies.com and ReptileEvolution.com) have further cemented these relationships.
Gauthier (1986) defined “Ornithodira” as all forms closer to birds than to crocodiles. Here, based on the topology recovered by the large reptile tree (with an unmatched gamut) this definition is redundant with an earlier one (Gauthier and Padian 1985) made for Ornithosuchia.
Sereno (1991) re-defined “Ornithodira” as the last common ancestor of the dinosaurs and the pterosaurs, and all its descendants.
Here, based on a larger tree that separates the pterosaurs from the dinosaurs on separate branches that divided in the earliest Carboniferous, the definition of Ornithodira is redundant with Reptilia. This can be easily tested with far fewer taxa. Not sure why paleontologists have not done so. Tradition is cozy and comfortable, but no discoveries have ever been made in comfort.
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.
Fraser N 2006. Dawn of the Dinosaurs: life in the Triassic. Indiana University Press, 310 pp.
Gauthier JA and Padian K 1985. Phylogenetic, functional, and aerodynamic analyses of the origin of birds and their flight. In M. K. Hecht, J. H. Ostrom, G. Viohl, and P. Wellnhofer (eds.), The Beginnings of Birds: Proceedings of the International Archaeopteryx Conference, Eichstätt 1984. Freunde des Jura-Museums Eichstätt, Eichstätt 185-197
Gauthier JA 1986. Saurischian monophyly and the origin of birds, In Padian K editor. The Origin of Birds and the Evolution of Flight, 1–55. Memoirs Calif Acad Sc 8.
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.
Kellner AWA 1996. Remarks on Brazilian dinosaurs. Memoirs of the Queensland Museum 39(3):611-626
Peters D 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336
Senter P 2004. Phylogeny of Drepanosauridae (Reptilia: Diapsida). J Syst Palaeo 2: 257–268.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. J Vert Paleo 11 (Supp) Mem 2: 1–53.
Unwin, DM 2006. The Pterosaurs From Deep Time. Pi Press. 347 pp.