A Blind Eye Toward Pterosaur Origins

It is indeed unfortunate that it has come to this.
Pterosaur experts have turned a blind eye toward finding the origin of pterosaurs. Even in this modern day of phylogenetic analysis, professors are ignoring all the likely suspects. Not sure why. It only helps the Creationists (who posted this video) when they don’t do their jobs. Case in point:

Dr. Gunther Viohl

Figure 1. Dr. Gunter Viohl speaking on the lack of data on pterosaur origins. Click to view video.

Here Dr. Gunter Viohl reports, “Their ancestors are not known.” In the same video Dr. Peter Wellnhofer reports, “It is a mystery, which group of reptiles prior to the Triassic might have given rise to the pterosaurs actually. So we don’t actually have the ancestor to the pterosaurs in the fossil record.” This video plays into Creationist dogma (as you’ll see when you view it), but the larger point should not be dismissed. In our search for pterosaur ancestors, the field of likely candidates can get narrowed to the same three likely suspects no matter which part of the body is chosen for inspection. Taken as a whole, using the concept of maximum parsimony, the case becomes iron-clad (see below) for a fenestrasaur origin (Peters 2000), which has been shunned like a crucifix on the neck of a vampire’s intended victim.

Peter Wellnhofer

Figure 2. Dr. Peter Wellnhofer reporting on the lack of data regarding the origin of pterosaurs. Click to watch video.

Here are the most striking homologies and convergences point by point — along with several candidate reptile taxa sharing the trait:

Basal pterosaurs had multicusped posterior teeth. Candidates: mammals, Longisquama. (I’m sure you can already see where this is going…)

Antorbital Fenestra
Basal pterosaurs had an antorbital fenestra without a fossa. Candidates: Proterosuchus, Chroniosaurus, Cosesaurus, Sharovipteryx, Longisquama.

Basal pterosaurs had an elongated and posteriorly displaced naris. Candidates: Cerritorsaurus, chanaresuchids, certain choristoderes, varanids, Huehuecuetzpalli and other tritosaur lizards, including tanystropheids and fenestrasaurs.

Basal pterosaurs had a short, sharp quadratojugal arising from the jugal and lightly connected to the quadrate. Candidates: certain Macrocnemus, Tanytrachelos, Cosesaurus, Sharovipteryx, Longisquama.

Sacral Number
Basal pterosaurs had four sacral vertebrae. Candidates: pareiasaurs, basal sauropterygians, Cyamodus, non-basal dinosaurs including birds, Scleromochlus, SaltopusCosesaurus, Sharovipteryx, Longisquama.

Basal pterosaurs had an attenuated tail with elongated centra (3x height) and chevrons parallel to the long axis of each centrum. Candidates: Basal birds, Huehuecuetzpalli and other tritosaur lizards, including tanystropheids and fenestrasaurs.

Ossified Sternum
Basal pterosaurs has an ossified sternum. Candidates: Lepidosauriformes (begining with Saurosternon and including fenestrasaurs).

Sternal Complex
Basal pterosaurs had a sternal complex comprised of a co-ossified sternum, interclavicle and wrap-around medially-overlapping clavicles. Candidates: Cosesaurus, Longisquama (still unknown and buried in Sharovipteryx according to Robert Reisz pers. comm.).

Basal pterosaurs had a strap-like scapula. Candidates: certain Macrocnemus, drepanosaurs, Cosesaurus, Sharovipteryx, Longisquama, protorosauria including archosauriforms.

Basal pterosaurs had a stem-like coracoid. Candidates: Cosesaurus, Sharovipteryx, Longisquama, derived crocodylomorphs and birds. If you restrict this character to those with a coracoid that inserted its ventral process into a sternal complex, then only fenestrasaurs are candidates.

Pteroid and Pre-Axial Carpal
Basal pterosaurs had a pteroid and preaxial carpal. Candidates: Cosesaurus (Peters 2009), Sharovipteryx, Longisquama.

Basal pterosaurs had fingers that increased in length from 1 to 4 with the fifth digit much smaller, a vestige at best. Candidates: Tanystropheids and Fenestrasaurs.

Basal pterosaurs had an anteriorly elongated ilium and a fused pubis + ischium (sometimes embayed). Candidates: Cosesaurus, Sharovipteryx and Longisquama.

Basal pterosaurs had a prepubic bone. Candidates: Cosesaurus, Sharovipteryx and Longisquama.

Basal pterosaurs had a tibia/fibula longer than the femur and the attenuated fibula was appressed to the tibia. Candidates: certain theropod dinosaurs in the lineage of birds, Scleromochlus, SaltopusSharovipteryx and Longisquama.

Basal pterosaurs had simple hinge ankles that included an unfused large astragalus and a smaller calcaneum without a tuber. Distal tarsals included only a large centralia, a large distal tarsal 4 and a small distal tarsal 3 (Peters 2000b). Candidates: Huehuecuetzpalli and the tritosaur lizards, including tanystropheids and fenestrasaurs.

Basal pterosaurs had metatarsals and toes that increased in length from 1 to 4 with the fifth metatarsal very short and the first two phalanges of digit 5 are very long. Candidates: Huehuecuetzpalli and the tritosaur lizards, including Macrocnemus and fenestrasaurs.

Extradermal Membranes
Basal pterosaurs (presumably) had extradermal membranes provided with aktinofibrils for support (because later pterosaurs with soft tissue preservation show this). Candidates: Cosesaurus (Peters 2009), Sharovipteryx and Longisquama.

This list of pterosaurian characters shared by tritosaur lizards, and most notably within that clade, the fenestrasaurs, is much longer than that of any other reptile taxon. Thus the rule of parsimony indicates that this is where we should be looking for pterosaur ancestors. Unfortunately, every paper and book (Unwin 2006) on the origin of pterosaurs has ignored the data and results of Peters (2000a, b, 2002, 2007, 2009, 2011). Why is this so? The answer is here in a large phylogenetic analysis. It can be tested. The specimens can be looked at. It’s time for pterosaur experts to take their blinders off.

Meanwhile we’re stuck with imaginary creatures that the experts seem to prefer (Unwin 2006, Bennett 2008). Ironically, these imaginary creatures are lizard-like, with sprawling hind-limbs, a morphology that Bennett (1996) discarded a while back. Interesting…

Remember, even turtles test closer to pterosaurs than archosaurs.

Hone and Benton (2007, 2008) did not view the specimens and discarded the results of Peters (2000b) to arrive at their bizarre and error-ridden supertree in which sister taxa do not resemble one another. Senter (2003) produced cartoonish drawings of specimens leading one to the conclusion that the specimens were not adequately examined. The status quo is a sad state of affairs that needs to be corrected. Peters (2000b) needs to be tested! …not ignored or shunned.

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 1996b. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoological Journal of the Linnean Society 118:261–309.
Bennett SC 2008.
Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E. Buffetaut & D.W.E. Hone (eds.), Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
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.
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 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 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, 1-279.
Unwin DM 2006. The Pterosaurs From Deep Time. Pi Press, New York. 347 p.


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