Evolution of the Pterosaur Palate – part 5: Eudimorphodon to Pterodaustro

Earlier we looked at basal pterosaur palatesdimorphodontoid palates, campylognathoid palates and pre-azhdarchid palates. Here in part 5 we’ll look at the pterosaur palate from Eudimorphodon to Pterodaustro (following the phylogenetic order recovered in the large pterosaur tree) which splits Dorygnathoidea in three). Scaphognathids will follow.

Evolution of the pterosaur palate from Eudimorphodon to Pterodaustro.

Figure 1. Click to enlarge. Evolution of the pterosaur palate from Eudimorphodon to Pterodaustro. The WDC specimen of Dorygnathus is shown twice, once as originally reconstructed by Osi et al. (2010) and once with a revised reconstruction with errors corrected.

Distinct from Eudimorphodon, the palate of Sordes was wider with more gracile palatal elements.

Dorygnathus, the Donau specimen
Distinct from Sordes, the palate of the Donau specimen of Dorygnathus was longer with larger teeth. The pterygoid had a lateral process. The ectopalatine had a posterior process.

Distinct from the Donau specimen, the palatal portion of the maxillae in Cacibupteryx extended further posteriorly with a triangular shape. The pterygoids were larger and more robust. The ectopalatines were shorter and more robust.
Dorygnathus, the WDC specimen
Osi et al. (2010) described the WDC specimen without providing a museum number. The palate in ventral view seems midway between a triangle and a rectangle. The pterygoids were smaller. The ectopalatines were longer and not fused to one another, even those this is one of the largest dorygnathids.

Dorygnathus, the R156 specimen
This is largely conjecture based on landmarks on the lateral side of the R156 skull.

Dorygnathus purdoni
This 3D skull had a more gracile pterygoid with curled lateral processes. The ectopalatine was robust.

With giant premaxillary teeth, the long narrow rectangular palate of Angustinaripterus was more gracile with a longer posterior process of the ectopalatine. The vomers were more robust.

No. 40
The much smaller dorygnathid, no. 40, had a narrower rostrum with maxillary palate plates extending further posteriorly. The lateral processes of the pterygoids were more robust, serving as bases for the ectopalatines.

AMNH 5147
In this tiny pre-ctenochasmatid the rostrum was much narrower. In AMNH 5147 the two processes of each ectopalatine were nearly parallel to one another. The base of each ectopalatine emerged from the broad anterior process of each pterygoid. These essentially filled the posterior palate.

The anterior teeth were greatly enlarged in Gnathosaurus. The dorsal premaxilla was broader than the anterior maxilla, but the ventral premaxilla was relatively tiny and not expanded. The maxillary plates underlapped (in ventral view) the vomers for a third of their length and extended posteriorly to mid antorbital fenestra. The ectopalatines were robust and nearly twice the length of the much shorter and broader pterygoids.

Only the posterior palate is shown for Pterodaustro in figure 1. The maxillary plates extended to beyond the middle of the antorbital fenestra. The ectopalatine has a checkmark shape, nested at the anterior tip of the pterygoid’s lateral process.

As in the the azhdarchid lineage, the ctenochasmatid lineage gradually increased the length of the rostrum and the maxillary portion of the palate beneath the rostrum with a coincident reduction of the ectopalatine and pterygoid, which became increasingly oriented parallel to the cheeks.

One of my reasons for adding more dorygnathus taxa to the large pterosaur family tree was the apparent midpoint link Angustinaripterus provided between Dorygnathus and Gnathosaurus.

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.

Osi A, Prondvai E, Frey E and Pohl B 2010. New Interpretation of the Palate of Pterosaurs. The Anatomical Record 293: 243-258.

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