Evolution of the Pterosaur Palate – part 4: Eudimorphodon to Quetzalcoatlus

Earlier we looked at basal pterosaur palates, dimorphodontoid palates, and campylognathoid palates. Here in part 4 we’ll look at the pterosaur palate from Eudimorphodon to Quetzalcoatlus (following the phylogenetic order recovered in the large pterosaur tree) which splits Dorygnathoidea in three). Ctenochasmatids and scaphognathids will follow.

evolution of the pterosaur palate from Eudimorphodon to Quetzalcoatlus.

Figure 1. Click to enlarge. The evolution of the pterosaur palate from Eudimorphodon and Sordes to Quetzalcoatlus. Following a trend toward enlargement of the teeth, the rostrum elongated and the teeth were reduced to absent as the roof of the palate increased its proportion.

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.

By the way…
The Dorygnathus palate described by Osi et al. (2010) and shown earlier, is not in this lineage, but will be covered in another lineage within Dorygnathus, part 5 (Eudimorphodon to Pterodaustro).

Dorygnathus, the SMNS 51827 specimen
In the SMNS 51827 specimen of Dorygnathus the posterior skull was wider and the pterygoids were laterally bowed (a trait not seen in sisters). The posterior process of the ectopalatine was not so long.

Dorygnathus, the SMNS 50164 specimen
The maxillary portion of the palate extended further posteriorly in the SMNS 50164 specimen of Dorygnathus. The gracile palate bones became smaller as a result. The teeth, while still large, were smaller than in predecessors.

TM 10341
The tiny dorygnathid TM 10341 had embryonic proportions, including much smaller teeth, wings and tail. The skull was actually longer, unlike the pattern seen in several other smaller specimens following larger ones. The pterygoid was relatively longer and the ectopalatine was shorter.

No. 42
Typically mistaken for a Pterodactylus (Wellnhofer 1970), No. 42 is basal to the azhdarchidae and the flightless pterosaurs + Huanhepterus. The narrower rostrum, smaller teeth and more gracile palate elements all appear to be weight-saving traits on this long-necked stork-like yet still tiny pterosaur.

Sos 2179
Originally mistaken for a ctenochasmatid with a bump on its rostrum, the bump in Sos 2179 is actually a displaced premaxilla, here restored. Distinct from No. 42, the number of teeth is greatly increased to hundreds in each jaw all about the same size and shape.

Distinct from No. 42 the pterygoids of Zhejiangopterus were longer, straighter and essentially parallel to each other. The anterior head of the each pterygoid was robust. The ectopalatines were more gracile and their anterior tips inserted between the vomers and medial maxillary plates.

The much larger azhdarchid, Quetzalcoatlus had relatively longer skull with a longer proportion devoted to the medial (palatal) maxillary plates. The vomers were fused and expanded laterally, solidifying the palate. The lateral ectopalatines were shorter, thus the posterior elements, including the pterygoid, were even more parrallel, yet the space was increasingly filled up posteriorly.

The premaxilla, never including more than four teeth per side, becomes gradually smaller in this clade. The maxilla palatal plates really take over, meeting the vomers medially and extending further posteriorly. The pterygoids change from an inverted V-shaped to parallel elements. Not much change in the ectopalatines.

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.

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