Pathological camarasaurs and carnivorous ceratopsids
September 16, 2008
Want to see something scary?
I mean really scary?
OK, here you go: it’s McIntosh et al. (1996:fig. 31), showing the neural arch and spine of dorsal vertebra 6 of Camarasaurus grandis GMNH-PV 101 in anterior and posterior views:
I’m sure I need hardly point it out, but this neural spine has two badgering great holes in it! What the heck? This feature is seen on both sides of the vertebra, so it can’t be a simple pathology; yet it doesn’t occur in any of the other preserved dorsals (7-12) — nor, indeed, in any other sauropod vertebra known to me, camarasaur or otherwise.
McIntosh et al. (1996:13) see this morphology in terms of “a slender, round rod extending down from the metapophyseal to articulate with the lamina arising from the epipophyseal” — in other words, that the lateral borders of the holes are novel additions to the bone, rather than the holes themselves being novel excavations in the bone — although as we’ve seen before, these things can be a bit six-of-one-and-half-a-dozen-of-the-other. They draw a parallel between this novel strut and the “diagonal ligament” described by Jensen (1988) in “Cathetosaurus” (= Camarasaurus) lewisi, but assert that the struts are bone, not tendon or ligament.
There is, however, a more parsimonious explanation for this novel morpology: as shown here in an actual scientific reconstruction, it appears that this Camarasaurus individual was attacked by a chasmosaurine ceratopsid, and that the skull of the latter become embedded in the sixth dorsal vertebra of the former — the probable cause of death:
[Camarasaurus supremus median dorsal from Cope (1878:fig. 5); Chasmosaurus russeli skull from Godfrey and Holmes (1995:fig. 1b).]
I see this as convincing vindication for Mark Witton’s speculation on facultative carnivory in ceratopsids.
- Cope, Edward Drinker. 1878. On the saurians recently discovered in the Dakota Beds of Colorado. The American Naturalist 12 (2):71-85.
- Godfrey, Stephen J., and Robert Holmes. 1995. Cranial morphology and systematics of Chasmosaurus (Dinosauria: Ceratopsidae) from the Upper Cretaceous of Western Canada. Journal of Vertebrate Paleontology 15 (4):726-742.
- McIntosh, John S., Clifford A. Miles, Karen C. Cloward and Jeffrie A. Parker. 1996. A new nearly complete skeleton of Camarasaurus. Bulletin of Gunma Museum of Natural History 1:1-87.