New Caiuajara paper documents crest growth during ontogeny

Sunday, December 18, 2022 13:09

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Pterosaurs, like most lepidosaurs, grew isometrically.
In other word, juveniles hae adult proportions. We know this from ontogenetic series demonstrated in Pterodaustro and Zhejiangopterus and from ready-to-hatch, full-term embryos like the IVPP V13758 and JZMP-03-03-2 specimens. Baby pterosaurs were able to fly shortly after hatching from a leathery egg, another lepidosaur trait. Mother pterosaurs retained the maturing egg safely within their body, another lepidosaur trait.

Figure 1. Ontogenetic skull and crest development in Tupuxuara. Note the eyes are small and the rostrum is long in juveniles. Only the crest expands and only posteriorly.

Large-crested tapejarids provide a notable exception.
Juvenile tapejarids do not hatch with the large crest of adults. Those crests develop later, allometrically during maturation. Large crests would not fit inside a pterosaur egg shell. This was first demonstrated in Tupuxuara (Fig 1), later in Tapejara (Fig 3) and most recently in Caiuajara (Fig 2), as documented by Manzig et al 2014 and Canejo et al. 2022.

Figure 2. Several Caiuajara skulls to scale and scaled to fit a more complete juvenile skull, CP.V 8175. At least one of these is not like the other. Note the allometric development of the huge premaxilary crest, which could not fit within a normal pterosaur egg.

From the Canejo et al 2022 abstract:
“Here we describe a new specimen from the pterosaur graveyard site, which corresponds to the most complete skull of Caiuajara dobruskii known so far. The new specimen preserves the posterior portion of the skull, allowing a better comprehension of its morphology and provides an appreciation of the anatomic structures of the basicranium, enabling better interpretation of this region. A variability in the premaxillary crest is also noted in different specimens of Caiuajara, which might be interpreted as sexual dimorphism or ontogenetic variability.”

Figure 1 frame 5 shows the distinctly different fused premaxilla+maxilla+nasal that Canejo et al found within the Caiuajara bonebed. The authors consider this specimen conspecific with Caiuajara dobruskii, despite morphological dissimilarity. Also see the posterior skulls in figure 5.

Presently no pterosaurs clearly demonstrate sexual dimorphism or ontogenetic variability although these are widely held myths. All such changes have been shown to be phylogenetic or individual. In other words, no two pterosaurs with distinctly different (dimorphic) crests have phylogenetically nested together.

It is also likely that individual variability might be high because no two pterosaurs (so far) have been shown to be identical. This follows the pattern of many other extinct and extant taxa from ceratopsians to tyrannosaurs. This does not discount the isometry demonstrated by Pterodaustro and Zhejiangopterus, which are virtually identical, except for size differences. The first juvenile Rhamphorhynchus was identified in phylogenetic analysis because it was phylogenetically identical to a much larger specimen. Pterosaur referees refused to let this data become published in order to preserve the status quo they teach from university textbooks.

Phylogenetically miniaturized adult pterosaurs,
many the size of other pterosaur hatchlings, have confused prior pterosaurs workers who have historically refused to add these specimens as taxa in phylogenetic analyses. Presently only the large pterosaur tree (LPT, 264 taxa) includes all relatively completely known pterosaurs, large and small, recovering a tree topology different than academic analyses that cherry-pick taxa. Who would be against adding taxa to verify phylogenetic results? So far it’s the PhDs. Their curiosity is strangely lacking.

Figure 3. Caiuajara size comparisons. There is quite a variety of tapejarids, approaching the variety in Pteranodon, Rhamphorhynchus and other pterosaurs. Note that in the larger Tapejara there is still a suture in the scapulocoracoid.

Reported here in 2014 when Caiuajara was first described:
“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.”

Figure 4. All that is known of Keresdrakon layered on top of a Quetzalcoatlus sp. specimen and the same ghosted and reduced to the size of Keresdrakon. These bones were also found in the Caiuajara bonebed.

Canejo et al 2022 report,
“The sole Brazilian site of ‘Cemite´rio dos pterossauros’ is the only bone bed known so far
where more than one pterosaur species was found: the already mentioned Caiuajara dobruskii
Manzig et al. 2014, which is the predominant species in the vertebrate assemblage; and Keresdrakon vilsoni Kellner et al. 2019.”

Two dinosaurs and a squamate were also found in the cemetery of at least two recognized pterosaur genera (Figs 2, 4). So this site was not exclusive to a single species of anything.

Figure 5. Two posterior skull specimens from the Caiuajara cemetary. Are these two conspecific? Canejo et al. say ‘Yes!”. Run these through phylogenetic analysis to find out.

Canejo et al 2022 report,
“As in all azhdarchoids, the lower jaw is toothless.”

This is a persistent myth. Simply by adding more taxa, as in the LPT, tapejarids are derived from dsungaripterids and germanodactylids, not azhdarchids (Fig 4), which arise from phylogenetically minizaturized dorygnathids in the LPT. Why don’t PhDs add taxa? Ask them. And while you’re at it, ask them why they refuse to test Cosesaurus and kin as pterosaur outgroup taxa. Their curiosity is strangely lacking.

References
Canejo L, Holgado B, Weinschu¨tz LC, Ricetti JHZ, Wilner E, Kellner AWA 2022. Novel
information on the cranial anatomy of the tapejarine pterosaur Caiuajara dobruskii. PLoS ONE
17(12): e0277780. https://doi.org/10.1371/journal. pone.0277780
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.