Basal Pterosaur Teeth and Their Genesis in Fenestrasaurs

Basal pterosaurs had a distinctive tooth pattern that had their genesis in the non-volant fenestrasaurs. You won’t find similar patterns in archosaurs.

Basal pterosaur and fenestrasaur teeth.

Figure 1. Click to enlarge. Basal pterosaur and fenestrasaur teeth. Only the fenestrasaurs demonstrate a gradual accumulation of pterosaurian traits, including the distinctive multicusped teeth of Triassic forms. Note:  the traditional reconstruction of the Eudimorphodon skull puts the premaxilla/maxilla suture ventral to the naris and just behind the last upper fang. Unfortunately this pattern is not seen in other pterosaurs, so this “suture” may be a crack. Another possibility is shown here. Note that sister taxa do not have widely separated anterior fangs. Dimorphodon does, but it is evolving on a different branch, toward the anurognathids.

Cosesaurus
The teeth of Cosesaurus were extremely homodont – except for those last three suborbital maxillary teeth, which were twice as anteroposteriorly long as the others. These evolved to become mult-cusped teeth in later taxa. Nearly all teeth contacted their neighbors.

Sharovipteryx
In Sharovipteryx we find the first hints of heterodonty with a pair of longer teeth ventral to the ascending process of the maxilla and multi-cusped teeth posteriorly. The anterior dentary teeth were procumbent and widely separated from one another. The posterior dentary teeth were slightly longer than any maxillary tooth.

Longisquama
The above dentary pattern was emphasized in Longisquama, in which the dentary teeth were much larger than the maxillary teeth and more teeth had more than one cusp.

MPUM 6009
In the most primitive known pterosaur, MPUM 6009, suborbital teeth did not develop. The standard four premaxillary teeth were present. Two anterior maxillary teeth were simple cones that were widely separated, but the rest had more than one cusp and were tightly packed. The maxillary teeth were slightly larger than the dentary teeth. The anterior dentary bends downward, producing incumbent anterior teeth.

Raeticodactylus
No maxillary teeth were simple cones in Raeticodactylus, only the premaxillary teeth. The same pattern appears in the dentary.

Austriadactylus cristatus
The teeth were overall much larger in Austriadactylus cristatus with four slightly recumbent premaxillary teeth emerging from a descending premaxilla. Four enlarged fangs were present ventral to the ascending process of the maxilla. The posterior teeth were serrated, not multicusped.

Austriadactylus? cristatus? (the Italian specimen)
This taxon had smaller teeth and does not appear to be congeneric with Austriadactylus cristatus. The anterior dentary bent down creating procumbent teeth.

Eudimorphodon ranzii
Two large premaxillary teeth and two small ones preceded two maxillary fangs in Eudimorphodon. These were succeeded by a battery of short multi-cusped teeth implanted side by side. Below the ascending process of the maxilla two of these teeth were enlarged to fangs. The dentary had a similar pattern with two fangs preceding a battery of short multi-cusped teeth.

Dimorphodon macronyx
This taxon developed four large premaxillary fangs. None of the maxillary teeth were multi-cusped. Three large dentary fangs preceded a set of tiny single-cusped teeth.

There is is huge variety of tooth morphologies in Triassic pterosaurs, hinting at a broader spectrum of taxa yet to be found. No post-Triassic taxa had multi-cusped teeth. Non-pterosaur fenestrasaurs demonstrate a gradual accumulation of pterosaurian tooth traits that you’ll never find in archosaurs (wherein most paleontologists hope to find the ancestors of pterosaurs). Since no one but yours truly has explored the ancestry of pterosaurs within the fenestrasaurs, there are no other references for the genesis of their distinctive teeth. Sorry. Maybe someday.

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.

References
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.


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