The equivocal epipophyses of Cf. Quetzalcoatlus
February 5, 2015
It’s well known that there is good fossil material of the giant azhdarchid pterosaur Quetzalcoatlus out there, but that for various complicated reasons it’s yet to be published. But as part of our ongoing quest for pterosaur epipophyses, I have obtained these photos of a pretty well preserved single cervical, probably C3, which is either Quetzalcoatlus or something pretty darned close.
My thanks go, in chronological order, to Rob Knell of QMC for taking the photos; to Don Brinkman for permission to share them publicly; and to Mike Habib (the USC one, not the Elsevier one) for passing them on to me. (The composition is my own work, which anyone is free to reuse so far as I’m concerned.)
Here’s what Mike Habib says about the specimen:
… well preserved TMP azhdarchid cervical vertebra. It is likely a CIII vert, and appears to be from an animal very similar to the small morph of Quetzalcoatlus in overall morphology. The associated humerus is just about an exact match. This cervical, however, does not quite match the proportions of any of the Q. sp. cervical verts, though that’s not a surprise given that the animals come from different horizons. There is a much larger, but poorly preserved cervical vert at the TMP as well (a Q. northropi sized animal, give or take).
Here are Mike’s measurements:
- maximum length: 142.2 mm
- minimum mediolateral breadth: 39.3 mm
- minimum dorsoventral breadth: 27.4 mm
- midshaft mediolateral breadth 40.0 mm
- midshaft dorsoventral breadth 27.0 mm
- mediolateral breadth across prezygapophyses: 65.6 mm
- mediolateral breadth across postzygapophyses: 68.5 mm
- dorsoventral breadth at postzygapophyses: 35.8 mm
(I mean those are the measurements that Mike provided for the vertebra, not the measurements of Mike himself. He’s much bigger than that.)
So does this specimen have epipophyses? Frustratingly, there don’t seem to be lateral or posterior-view photos, so it’s very hard to tell from these dorsal and ventral ones. Happily, the same specimen was illustrated and briefly described by Godfrey and Currie (2005:294-299), along with several other less well-preserved cervicals — so we do have drawings of these other views:
(The specimen number given here is slightly different from that given for the photos, but matches the label in the ventral-view photo. I assume that the leading “93” part of the specimen number is a year, and that it’s sometimes but not always given in four digits.)
The text of the description does not mention epipophyses, and skips very lightly over the whole postzygapophyseal area. But figures 16.1B (lateral) and 16.1E (posterior) both seem to show distinct bulbous eminences well above the postzygapophyseal facets. I think these have to be epipophyses. So Mark Witton’s caution not to write off azhdarchid epipophyses on the strength of their apparent absence in Phosphatodraco proves well-founded.
What is the moral here?
The more we look for epipophyses, the more we find them.
Which will be strangely familiar to anyone who remembers our experience with caudal pneumaticity in sauropods, which was: the more we looked for it, the more we found it.
If we have an SV-POW! motto (other than “sauropods are awesome”, of course), it’s “Measure your damned dinosaur!“. But if we had a third motto, it would be like unto it: look at your damned dinosaur. Or pterosaur, as the case may be. The odds are, you’ll see things you weren’t expecting.