Same or Different? When Should You Invent a new Genus? or Just Add a Species? Or Revise the Whole Clade?
Now that new pterosaurs are being added to the large pterosaur tree on a fairly constant basis, it’s time to figure out what to name them.
In the old days everything was named “Pterodactylus,” no matter what it was. Sharp-eyed observers soon figured out that there were differences that set certain specimens apart and these were then renamed. Others have not yet been widely recognized as distinct, but they need to be (Fig. 1).
Figure 1. Click to enlarge. The Pterodactylus lineage and mislabeled specimens formerly attributed to this “wastebasket” genus
Nowadays, new pterosaurs distinct from all others are being given new generic names, and that’s a good thing. However some of the new specimens nest within long lists of other genera. Others are given new species names within certain genera without nesting near those genera. The problem is a result of the incompleteness of all previously published pterosaur trees. They simply do not include enough taxa. They have a priori deleted all tiny specimens and all congeneric variations that, in the large pterosaur tree, provide clues to the evolution of more derived variations, some of which are distinct genera, as in the Campylognathoides/Rhamphorhynchus transition.
Some examples
MPUM6009 was considered a Eudimorphodon and a Carniadactylus despite nesting far from both genera. MCSNB 8950 was considered a Eudimorphodon, but nested with anurognathids.
Nesodactylus nested within the genus Campylognathoides. Bellubrunnus and Qinglongopterus nested within the genus Rhamphorhynchus.
Fenghuangopterus, Sericipterus and Cacibupteryx nested within the genus Dorygnathus.
Eosipterus and Cuspicephalus nest within the genus Germanodactylus.
Kellner (2010) renamed one Pteranodon, Dawndraco, but it remains surrounded by other Pteranodon specimens.
The question is, do we revise all the old genera and give them new names now that we know how distant some were from each other? Or do we retain those genera and take away the new generic names of the new specimens between them to reflect their traditional generic nesting?
Now all this doesn’t take into account marginal generic names, like Ningchengopterus at the base of the Pterodactylus clade or Muzquizopteryx at the base of the Nyctosaurus clade. These names are likely to be valid because they are distinct genera, but so are many of the species within Pterodactylus and Nyctosaurus. If they were modern birds, not prehistoric pterosaurs, their differences would be recognized.
Part of the historical problem, of course, goes back to Chris Bennett and others who considered smaller species to be immature forms of larger species without adequately describing them or placing them in analysis. It turns out that the vast majority of those where simply smaller forms that were evolving to become the larger forms – or vice versa.
It’s a problem. It needs to be recognized and dealt with. But it will only be recognized if pterosaur specimens are not a priori deleted from analysis for whatever reason.
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
Kellner AWA 2010. Comments on the Pteranodontidae (Pterosauria, Pterodactyloidea) with the description of two new species. Anais da Academia Brasileira de Ciências 82(4): 1063-1084.
2012-12-02 19:42:27
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