Chaoyangopterids!

It’s a good time for pterosaur enthusiasts. Recent months have seen the publication of a bunch of significant papers. We’ve had the wonderfully complete second specimen of the weird Anurognathus, Andres and Ji’s thorough cladistic analysis of pterodactyloids, tiny little Nemicolopterus, the stunning basal form Raeticodactylus, and most recently Mark Witton and Darren Naish’s paper putting ahzdarchids on the ground as predatory, ‘mega-storks’. And now we have Shenzoupterus chaoyangensis, another pterosaur from the seemingly boundless Early Cretaceous Jehol Group of Liaoning, China. The paper is accessible here: http://www.springerlink.com/content/lj46h69l5149w001/?p=797295b0e22045f780debf3a7d7e0911&pi=0
Shenzhoupterus is special, not just because it is another new, nicely preserved pterosaur but because it helps tie together a group of somewhat enigmatic and poorly-known pterosaurs. A bunch of toothless Liaoning pterosaurs have been described in recent years, starting with Chaoyangopterus and followed in short order by Jidapterus, Eopteranodon, and Eoazhdarcho. Each of these was described as a basal member of three different Late Cretaceous toothless lineages: the Nyctosauridae, Pteranodontidae and Azhdarchidae. This made a lot of sense, as we would expect earlier members of these highly derived lineages to show up in older rocks. The big phylogeny in Andres and Ji, turned this idea on its head by finding that all of these taxa were part of one large toothless radiation: the Azhdarchoidea, with all except Eopteranodon forming a clade that was the sister group to the Late Cretaceous Azhdarchidae. Now we have new Shenzhoupterus to bring them all (Eopteranodon included) and bind them. The new clade is now christened the Chaoyangopteridae. Shenzoupterus also gives us our first clear look at a chaoyangopterid skull, and what an odd skull it is. It looks at first glance like a basic azdarchid skull with the nasal aperture of a brachiosaurid sauropod (and a little pteranodontid-like occipital spine for good measure).

The posterior retraction of the naso-antorbital fenestra (the nostrils and the antorbital fenestra of all pterodactyloid pterosaurs are united into a single opening) turns out to be a feature of other chaoyangopterids and is one of their main diagnostic characters.
One may well ask what these Chaoyangopterids were doing with their giant naso-antorbital fenestrae. One obvious hypothesis is that it increased the depth of the skull for display purposes, thus achieving much the same result as the cranial crests of other azhdarchoids like tupuxuarids but in a totally different way. However I prefer the idea that the opening housed a hyperenlarged nasal vestibule that also developed in a number of other Mesozoic archosaur groups (eg. macronarian sauropods, lambeosaurine hadrosaurs and ceratopsids). What were they doing with such big noses? Good question, the short answer is we don’t know, but I wonder if it isn’t to do with heat exchange and/or water reclamation while breathing. A fertile area for future research perhaps?


Andres, B.; and Ji Q. (2008) A new pterosaur from the Liaoning Province of China, the
phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae. Palaeontology 51 (2): 453-469.

Lü J, Unwin DM, Xu L, Zhang X (2008) A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications fro pterosaur phylogeny and evolution. Naturwissenschaften DOI 10.1007/s00114-008-0397-5.