New Paper on Pterosaur Pelves part 2

Yesterday in part 1 of this post we reviewed a new paper on pterosaur pelves by Hyder et al. (2012). Today we’ll continue.

The Anurognathidae to scale.

Figure 1. Click to enlarge. The Anurognathidae to scale.

Hyder et al. report, “…the anurognathid pelvis remains poorly known and all examples are preserved in relatively uninformative dorsal views.” This is not true. Those pelves have just not been traced and reconstructed in the literature, which appears to be where Hyder et al. got their data. Close examination employing DGS (digital graphic segregation) revealed the shapes of several anurognathid pelves seen here as a group (click here to see them individually). Hyder et al. report, “the ischia and the pubes are mostly unfused, a feature reflecting the immaturity of the best-known Anurognathus specimen.” This is not true. All anurognathids fuse the pubis and ischium. In the flathead anurognathid, SMNS 81928, mislabeled Anurognathus by Bennett (2007), the pubis and ischium are sutured, not fused. Since embryo pterosaurs were virtually identical to adult pterosaurs, and tiny pterosaurs were no larger than embryos of larger pterosaurs (as in birds and bats) there is currently no way (other than phylogenetic analysis or an eggshell) to tell the maturity levels of a pterosaur.

Campylognathoidids and kin
Hyder et al. (2012) report, “to our knowledge, only one complete pelvis is known but difficult to interpret…” I found several, starting here, and then one should include Nesodactylus as well. Hyder et al. (2012) report, “What can be seen of the pelves in Eudimorphodon, Carniadactylus and Campylognathoides suggests the preacetabular processes of some may be short.” Not true, and Carniadactylus is a proto-anurognathid. It doesn’t belong with this group. All members had a substantial preacetabular process. Campys have a particular combination of a very short pubis and the large prepubes among all pterosaurs. Throughout their evolution the ischium became more robust.

The MBR 1905.15 specimen of Dorygnathus

Figure 1. The MBR 1905.15 specimen of Dorygnathus. traced, reconstructed and according to Hyder et al. (2012).

Rhamphorhynchus and Dorygnathus
Hyder et al. (2012) follow several recent studies that lump these two taxa together, and one recent blogger couldn’t correctly identify a skeletal model, but these two taxa both share a common ancestor in tiny Eudimorphodon comptonellus and several intervening taxa on both branches. Hyder et al. (2012) considered these pelves similar, and they are, more less, sans the prepubes, which are completely different in morphology. The illustration of the MBR specimen of Dorygnathus presented by Hyder et al. (2012, Fig. 1) appears to fill in certain gaps that were generally present on other Dorys. They also appear to have filled in the gap between the ilium and pubis, lengthening it somewhat.

Darwinopterus and kin

Unfortunately Hyder et al. (2012) accepted prior drawings of two pelves in Darwinopterus rather than testing the tracings.

Darwinopterus linglongtaensis pelvis in situ and reconstructed.

Figure 2. Darwinopterus linglongtaensis pelvis in situ and reconstructed. The degradation of the fossil and the apparent overlapping of elements makes this one difficult. The only solution is to reduce the autapomorphies, if possible.

Hyder et al. (2012) report, “The pelvis of Darwinopterus modularis is known in forms with both closed and open pelvic canals (ZMNH M8782 and M8802, respectively; Lü et al. 2010, Lü and Fucha 2011).” Since Darwinopterus would have had a cloaca, a closed pelvic canal is not possible. They must have meant something else. They also report, “D. robustodens also has a unique preacetabular morphology among pterosaurs, being not only relatively robust, but arcing dorsally so that its termination points anteroventrally.” 

Revised January 25, 2014:
Always consider the possibility of a misinterpretation if you found something “unique” because that’s not the way evolution works. Here are the two interpretations of the D. robustodens pelvis and prepubis. More details on this here.

Figure 5. Darwinopterus robustodens pelvis as originally reconstructed (gray scale) and as recovered using DGS (color).

Figure 3. Darwinopterus robustodens pelvis as originally reconstructed (gray scale) and as recovered using DGS (color). A little more room for the egg to emerge in the new reconstruction and not so autapomorphic (unique). 

More tomorrow.

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.

Hyder ES, Witton MP and Martill DM 201X. Evolution of the pterosaur pelvis. Acta Palaeontologica Polonica 5X (X): xxx-xxx.

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