We’ll call this:
“When discovery confirms heretical hypotheses.”
Another pterosaur bone bed,
this time with subadults and juveniles (no eggs or hatchlings) of a new tapejarid, Caiuajara dobruskii (Manzig et al. 2014). Contra traditional paradigms, there is no indication of a large orbit and short rostrum in juveniles (confirming earlier posts here and at reptileevolution.com. Yes, the crest developed in adults, because it wouldn’t have fit inside the eggshell! At least 47 individuals here. Smallest were twice the size of hatchlings, one quarter the size of adults.
you can’t tell the females from the males. All had crests.
Bone beds are great for individual bone size comparisons, but difficult for creating reconstructions as small individuals are mixed in with large ones. From Manzig et al. (2014) “The presence of three main levels of accumulation in a section of less than one meter suggests that this region was home to pterosaur populations for an extended period of time. The causes of death remain unknown, although similarities with dinosaur drought-related mortality are striking. However, it is also possible that desert storms could have been responsible for the occasional demise of these pterosaurs.”
The size of the crests, both below and above the jaws, became larger with age. Most of the individuals were young with only a few adults present.
The authors found no allometry during ontogeny in post-cranial elements, but adults appear to be more robust and the scapula fused to the coracoid in adults only. This confirms what I’ve found in the fossil record in Zhejiangopterus, Pteranodon, Pterodaustro and generally in phylogenetic analysis. Now, after so much evidence, I hope the naysayers will give the hypothesis of isometry during ontogeny in pterosaurs its day in court.
Caiuajara is a small tapejarid, very similar to other tapejarids. This brings up the subject of lumping and splitting with nomenclature, whether a new genus is warranted or not. Is Caiuajara just another species of Tapejara? If not then we need to start splitting up other genera clades containing a wide variety of morphologies as in Rhamphorhynchus, Pteranodon, Germanodactylus, Darwinopterus and other pterosaurs, in which essentially, no two are identical. I’ll leave that to the experts. It’s going to take more than consensus.
A little speculation
Here we have a large number of juveniles (not hatchlings) and only a few adults in a sandy environment sometimes flooded by rising waters from a nearby lake. What does this mean?
A little backstory:
Pterosaur eggs are large enough that only one could be produced at a time, and held within the mother until just prior to hatching. So the large number of juveniles in this case (no hatchlings here) huddling together, did not belong to a single set of parents. The authors were right, pterosaurs of a certain size (perhaps hatchlings, but up to twice the size of hatchlings in this case) were able to fly. Since they were hatched individually the hatchlings/juveniles sought each other out at an early age, and sought out the company of older, larger tapejarids. Those crests made identification easy. It did not matter that the adults were their parents or not (distinct from the nuclear family illustration at Nat Geo) because the numbers don’t match up. Now IF the adults were found in a distinct layer from the juveniles, the speculation about the adult influence has no basis in evidence.
Manzig PC et al. 2014. Discovery of a Rare Pterosaur Bone Bed in a Cretaceous Desert with Insights on Ontogeny and Behavior of Flying Reptiles. Plos ONE 9 (8): e100005. doi:10.1371/journal.pone.0100005.