Earlier we looked at the evolution of the pterosaur palate from pre-pterosaurs to basal pterosaurs and from Dimorphodon to the Anurognathidae. Today we’ll look at the next clade: Eudimorphdon + Campylognathoides + Rhamphorhynchus. Surprisingly, for as many Rhamphorhynchus specimens that are known, too few preserve an exposed palate. If you have any, please send them!
Campylognathoides (SMNS 11879) had greatly enlarged eyes, which is reflected in the posterior expansion and anterior narrowing of the palate and a reduction and narrowing of the ectopalatine.
Campylognathoides (CM 11424) likewise has a narrow ectopalatine, but more robust.
The most basal Rhamphorhynchus, No. 28 in the Wellnhofer (1975) catalog, was a sister to Campylognathoides (CM11424) and this is reflected in the palate, which is identical, but shorter and wider.
The second most basal Rhamphorhynchus, the BMM specimen, was smaller than No. 28 and the proportions of the palatal elements were shorter still. The premaxilla was not pointed at all, but was transverse in orientation, more like an anurognathid. A big change in the pterygoid produced an enlarged pterygoid with a new lateral process and contact with the jugal.
In the two more derived Rhamphorhynchus palates, No. 55 and No. 89 in the Wellnhofer (1975) catalog (Fig. 1), the premaxilla became pointed again, the pterygoid was not so large and the lateral process of the pterygoid becomes longer. The quadrates had a greater angle of posterior lean and this is reflected in seeing their posterior aspects becoming increasingly ventral.
Here the phylogenetic size reduction led to a more embryonic short snout. The succeeding phylogenetic size enlargement (with longer embryonic development) led to a longer snout.
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.
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.