Can You Really Tell a Female Pterosaur by its Pelvis?
Dr. S. Christopher Bennett (1991, 1992) identified a rather large and disassociated Niobrara pelvis (KUVP 933) as a Pteranodon female pelvis. It had a larger pelvic opening than any other pelvis identified as Pteranodon. And it was slightly smaller. Unfortunately it continues to be the ONLY pelvis identified as a female Pteranodon, despite the odds against finding only one female pelvis among all the others found. Earlier, I identified the pelvis as a large Nyctosaurus pelvis (Fig. 1) due to morphological similarity. Here (Fig. 1) are the pelves under consideration, for your consideratrion:
The evolution of a small crest and small size toward larger crests and larger overall size has been plotted phylogenetically, demonstrating no size differences among gender and no deeper pelvis among half of the specimens found. Only phylogenetic differences can be accounted for at present with smaller Pteranodon typically nesting more primitively.
Due to the crushing angle, the Darwinopterus mother pelvis is difficult to reconstruct accurately, but it appears to be no deeper than that of other Darwinopterus specimens and no deeper than the pelvis of other sisters. The pelvis produced an egg that contained an embryo 1/8 the size of the adult, a pattern duplicated in Pterodaustro, the only other adult/embryo association.
So far, no matter what anyone tries to tell you, we can’t tell a female pterosaur from the pelvis or any other part of its morphology, other than the presence of an egg between the thighs. Maybe someday. Not yet.
Two more mother pterosaurs have surfaced. Ornithocephalus (Fig. 3) has what appears to be an egg ejected from her pelvis.
Anurognathus (Fig. 4) has a curled up embryo ejected from her pelvis. We looked at this specimen earlier.
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 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.