Variation within Dorygnathus – part 2

Kevin Padian (2008) on Dorygnathus banthensis represents the latest traditional thinking on this genus and species. We’re expanding on that with multiple reconstructions and a phylogenetic analysis, both lacking previously. Yesterday was part 1.

Figure 1. Click to enlarge. Rhamphorhynchus and Dorygnathus compared. Here we see basal taxa and middle of the evolutionary sequence taxa. R has a larger sternum in all cases.

Figure 1. Click to enlarge. Rhamphorhynchus and Dorygnathus compared. Here we see basal taxa and middle of the evolutionary sequence taxa. R has a larger sternal complex, smaller antorbital fenestra, longer m4.1  and shorter neck in all cases. The other distinctions are less obvious.

Often confused with or mistakenly related to Rhamphorhynchus
Dorygnathus
 (Fig. 1) and Rhamphorhynchus both shared big procumbent teeth by convergence. Whereas Rhamphorhynchus is known from several sizes (falsely considered ontogenetic by those who have not performed a phylogenetic analysis on clade members), Dorygnathus is not well known for size differences (Fig. 2), but there are some small ones and large ones.

Sericipterus (Andres et al. 2010, Fig. 2) is larger than the others, but it is not considered congeneric. Andres et al. (2010) considered it closest to Harpactognathus and Angustinaripterus (Fig. 2), both pre-ctenochasmatid dorygnathids. Their tree found these three taxa and Cacibupteryx to be derived from a sister to Dorygnathus, which is duplicated in the large pterosaur tree, only with more intervening and related taxa.

Looking for “juveniles,” but didn’t find any
Curious, I wondered if the small “Hauff” specimen would nest with one of the other larger specimens and so be considered a possible juvenile. So I ran the analysis. Instead, the Hauff specimen nested at the base of the clade, derived from a sister to the equally small Sordes (Fig. 1). This is not unexpected, but follows size patterns seen in most, if not all, major pterosaur clades with smaller specimens at the bases of distinct clades and genera. This went unnoticed in Dorygnathus until now.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you're a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangopterus. So Dorygnathia survived to the Maastrichtian.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you’re a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangnathus. So Dorygnathia survived to the Maastrichtian. A small one, the Hauff specimen, is basal. There is also a clade leading to a large Sericepterus that did not lead to other clades. The variety here is comparable to the Rhamphorhynchus clade.

SMNS 558866 is also small (Fig. 1), but nests between two larger specimens. While sharing many traits with all other Dorygnathus specimens, it appears to have a unique morphology, so is not a juvenile of the R156 specimen or Cacibupteryx.

So no juveniles here!! (Same as in Rhamphorhynchus, they’re growing up in damp leaf litter far from ancient Geman seas). I would have liked to have discovered some juveniles here, but you have to let the data do the talking.

To lump? Or to split?
The Dorygnathus clade suffers from the same nomenclature problem that other pterosaur clades suffer from. Several professionally named “Dorygnathus” are phylogenetically separated from one another by more recently named novel genera. No prior phylogenetic analysis including more than one Dorygnathus was ever attempted before. That’s the main problem. As you can see, there is variety within this clade that was previously overlooked.

There is no more and no less variation here in Dorygnathus than in the present Pteranodon, Pterodactylus, Germanodactylus, Rhamphorhynchus, Eudimorphodon and other wastebasket taxa. Someday a grand poobah will straighten this all out for us and have his authority respected. I don’t care if the lumpers win or the splitters win, but the tree has to be acknowledged agreed upon before we get down to naming genera again. It’s getting very confusing out there.

Tomorrow we’ll talk about Dorygnathus’ most embarrassing trait, that tiny sternal complex.

References
Andres B, Clark, JM and Xing X 2010. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs’, Journal of Vertebrate Paleontology, 30: 1, 163-187.
Padian K 2008. The early Jurassic pterosaur Dorygnathus banthensis (Theodori, 1830). Special papers in palaeontology 80: 64 pp.

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