The Cretaceous birds and pterosaurs of Cornet: part II, the pterosaurs

It's always been clear that pterosaurs were present in the Cornet assemblage (for the background on Cornet and its archosaur fossils, you need to have read part I).

However, exactly what sort of pterosaurs are present at Cornet has been somewhat uncertain: the Late Jurassic ctenochasmatoid Cycnorhamphus, ornithocheirids and the Early Cretaceous Asian dsungaripterid Dsungaripterus were all reported from the assemblage during the 1980s (e.g., Jurcsák & Popa 1984) but, as with the birds, the remains on which these identification were based (currently housed at the Tarii Crisurilor Museum, Oradea) aren't great. In fact, most of the pterosaur bones from Cornet can't be conclusively identified beyond Pterosauria or Pterodactyloidea, and claims that such taxa as Cycnorhamphus are present can't be supported (Dyke et al. 2010) [art above by Mark Witton - a Tet Zoo exclusive (err, I think). It shows a group of dsungaripterids hounding an azhdarchid. The illustration is one of many that will appear in Mark's pterosaur book, currently in preparation. An excerpt is available here].

Some of the specimens are, however, particularly interesting. One incomplete humerus clearly had a proportionally long deltopectoral crest with a flaring apex (the apex is broken, so the precise shape of the crest can't be determined). In these respects the humerus is at least superficially like that of a nyctosaurid, an identification which would be a big deal given the specimen's age (other nyctosaurids are Upper Cretaceous, specifically Coniacian-Maastrichtian). Furthermore, the bone is small (only 35 mm long), so its owner presumably had a wingspan of less than 1.5 m. We don't know enough to say whether the Cornet specimen is from a nyctosaurid, but the possibility is a very interesting one. A few other elements have been suggested to be from other kinds of ornithocheiroid.

Nyctosaurids have become increasingly interesting in recent years, what with the recognition of the incredible antlered specimens described by Bennett (2003) [some discussion here] and the Coniacian Muzquizopteryx coahuilensis from Mexico (Frey et al. 2006) [the Muzquizopteryx holotype is shown in the adjacent image; from here]. One of the many interesting things about nyctosaurids is that they lacked the three small, clawed fingers normally present in pterosaurs. This might indicate they were more aerial than other members of the group, rarely walking or climbing.

One group of pterosaurs definitely present at Cornet are dsungaripterids, a group well known for their toothless jaw tips and particularly thick-walled hindlimb bones. Best known from central Asia, their fossils are also known from Chile and Germany. The Cornet remains aren't great - a left humerus and a partial maxilla - but they demonstrate the presence of this group in eastern Europe during the Berriasian (Dyke et al. 2010). Other dsungaripterids are known from the Berriasian: the pterosaur formerly known as Phobeter is thought to be Berriasian or Valanginian, while Unwin et al. (1996) reported Berriasian dsungaripterid material from the Okurodani Formation of Japan.

A tiny, early azhdarchoid: a section in which many bold statements are made

Ornithocheiroids and dsungaripterids are all very nice, but what might be the most interesting pterosaur fossil in the assemblage is a small, incomplete cervical vertebra, just 25 mm long [shown here; from Dyke et al. (2010)]. This vertebra seems to have been cylindrical for most of its length, it has a neural spine that is reduced to merely a low ridge, and its prezygapophyses are elongate and widely divergent. These features make the specimen look exactly like a tiny azhdarchid cervical vertebra (there are other, more detailed features backing up this interpretation as well), and this is what we conclude that it is (Dyke et al. 2010). When complete, it was perhaps something like 100 mm long, and therefore represents one of the smallest (though not the smallest) azhdarchid cervical vertebrae yet known. So, we have a tiny azhdarchid in the assemblage.

Does the vertebra belong to a juvenile? It's not possible to say as it doesn't preserve any features that might indicate this (for a while I thought that the bone had especially thick walls - a feature said by some pterosaur workers to be indicative of juvenile status - but the walls are as thin as they are in definite adults, and the apparent thickness of the walls is a trick caused by mineral infill).

The Berriasian age of the specimen makes it the oldest azhdarchid specimen yet to be reported (previously, the oldest published specimens were from the Albian). This not only indicates that azhdarchids originated earlier in the Mesozoic than previously thought, it also means that other neoazhdarchians (namely, thalassodromids and chaoyangopterids) and other azhdarchoids (namely, tapejarids) must have been around by the Berriasian too: again this is novel as it carries their lineages down to the start of the Cretaceous (previously, they seem to have debuted in the Barremian or thereabouts). So, we should now expect to find tapejarids, thalassodromids and chaoyangopterids in the Berriasian and Valanginian [simplified azhdarchoid cladogram (depicting one topology of several that have been recovered) shown below. Pterosaur images by Mark Witton]. As usual, bring on those fossils. Lonchodectids - which seem to be the sister-group to Azhdarchoidea - also get an extended ghost lineage as a result of this discovery.

And if all of this seems an awful lot to stack up on a 25-mm-long fragment of a single vertebra, it is. At SVPCA 2010, Paul Barrett discussed what he termed the Barrett Incompleteness Index (BII): a term coined by one of his former PhD students* to describe how the incompleteness of any given fossil exponentially increased the odds that Paul would publish a paper on it. It isn't lost on me that all of the Cornet bird and pterosaur fossils might potentially score highly on the BII (though whether Paul would be interested in scrappy bird and pterosaur fossils is, of course, another question).

* You know who you are. Jo.

And that's the end of that chapter!

So, we saw in the previous article that the various grandiose claims made about the Cornet birds - that they might include archaeopterygids and neornithines - cannot be substantiated. Nevertheless, there seem to be some interesting birds in the assemblage, most notably a possible hesperornithine. As for the pterosaurs, the presence of dsungaripterids is confirmed, and the apparent presence of a small azhdarchid - albeit represented by fragmentary remains - is particularly interesting, given that it might tell us interesting things about the origin of this group, and perhaps about the timing of the azhdarchoid radiation [assortment of Cornet pterosaur bones shown in adjacent figure, from Dyke et al. (2010)].

Finally, what's with the pretty picture I've used in both of these articles? It's something I knocked up to make the articles look more interesting (thanks to Tim Morris for colourising); I hope you can forgive me for such crass popularising. The scene is set in a flooded lowland where ferns, cycads and other typical Early Cretaceous plants dominate the flora. Cornet was at equatorial latitudes during the Berriasian, so I should perhaps have made things look more tropical. Among the animals, we see a semi-hypothetical ornithurine bird at bottom left (it's meant to be a primitive, volant hesperornithine, and is based on the Enaliornis-like bone discovered at Cornet). An azhdarchid and dsungaripterid are shown in the middle of the picture; a generic pygostylian bird and ornithocheiroid pterosaur are shown flying overhead, and the iguanodontian Owenodon is shown in the background. For more on the picture, see the Tet Zoo facebook page.

For part I on the new Cornet paper go to...

• The Cretaceous birds and pterosaurs of Cornet: part I, the birds

And for previous Tet Zoo articles on pterosaurs see...

• The Wellnhofer pterosaur meeting, part I
• It could look a giraffe in the eyes
• The Wellnhofer pterosaur meeting, part II
• The Wellnhofer pterosaur meeting, part III
• Terrestrial stalking azhdarchids, the paper
• Shemhazai and other flightless pterosaurs
• Come back Lank, (nearly) all is forgiven
• Pterosaurs breathed in bird-like fashion and had inflatable air sacs in their wings
• A month in dinosaurs (and pterosaurs): 4, flaplings and head-sails anew
• A month in dinosaurs (and pterosaurs): 5, pterosaurs vs birds, or not... or is it?
• Darwinopterus, the remarkable transitional pterosaur
• Giant pterosaurs invade London, Summer 2010
• Pterosaurs, err, indoors (the Summer 2010 exhibition)

Refs - -

Bennett, S. C. 2003. New crested specimens of the Late Cretaceous pterosaur Nyctosaurus. Paläontologische Zeitschrift 77, 61-75.

DYKE, G., BENTON, M., POSMOSANU, E., & NAISH, D. (2010). Early Cretaceous (Berriasian) birds and pterosaurs from the Cornet bauxite mine, Romania Palaeontology DOI: 10.1111/j.1475-4983.2010.00997.x

Frey, E., Buchy, M.-C., Stinnesbeck, W., González, A. G. & di Stefano, A. 2006. Muzquizopteryx coahuilensis n.g., n. sp., a nyctosaurid pterosaur with soft tissue preservation from the Coniacian (Late Cretaceous) of northeast Mexico (Coahuila). Oryctos 6, 19-39.

Jurcsák, T. & Popa, E. 1984. Pterosaurians from the Cretaceous of Cornet, Roumania. In Reif, W.-E. & Westphal, F. (eds) Third Symposium on Mesozoic Terrestrial Ecosystems, Short Papers. Attempto Verlag (Tübingen), pp. 117-118.

Unwin, D. M., Manabe, M., Shimizu, K. & Hasegawa, Y. 1996. First record of pterosaurs from the Early Cretaceous Tetori Group: a wing-phalange from the Amagodani Formation in Shokawa, Gifu Prefecture, Japan. Bulletin of the National Science Museum, Tokyo, Series C 22, 37-46.