Female Pterosaurs

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:

Female Pteranodon?

Figure 1. Pteranodon (on left column) and Nyctosaurus (right column) pelves. KUVP 933 (I) is closer to Nyctosaurus in morphology. It is not a female Pteranodon. Note the variation in Pteranodon pelves. Unfortunately we can only match a few pelves to skulls, but we can deduce that all four at left belonged to larger specimens, some with long crests. 

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.

The Sure Thing
The only sure female pelvis ever found is that of the female Darwinopterus (Fig. 2). That’s because it had an egg emerging from it.

Darwinopterus mother and premature embryo

Figure 2. Darwinopterus mother and premature embryo. Click to see in situ tracing.

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.

Bottom Line
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.

Addendum
Two more mother pterosaurs have surfaced. Ornithocephalus (Fig. 3) has what appears to be an egg ejected from her pelvis. 

Ornithocephalus pterosaur egg.

Figure 3. Ornithocephalus pterosaur egg. Click to see in situ specimen.

Anurognathus (Fig. 4) has a curled up embryo ejected from her pelvis. We looked at this specimen earlier.

Possible Anurognathus embryo, isometrically one-sixth the size of the adult. Wing bones are not identified here.

Figure 4. Click to enlarge. Possible Anurognathus embryo, isometrically one-sixth the size of the adult. Wing bones are not identified here.

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
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.

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