A paper soon to appear in PNAS (and not yet online) suggests that some dinosaurs might have been venomous. The title, however, leaves no wiggle room: “The birdlike raptor Sinornithosaurus was venomous.”
A team of scientists from China and Kansas noticed that a fossil specimen of the feathered theropod dinosaur Sinornithosaurus millenii (see pp. 40-44 of WEIT) had long maxillary teeth that were grooved (see Fig. 1 below). Such grooved teeth are often seen in venomous animals: glands secrete the venom into channels in the jaw, which deliver it to the base of the teeth. It then mixes with saliva and the toxic cocktail is drawn into the tooth grooves by capillary action. In venomous reptiles like the gila monster, these teeth deliver a poisoned bite that doesn’t kill the prey but puts it into a state of shock.
S. millennii also had a space on the jaw (“maxillary fossa”) that could have housed a venom gland, and jaw channels that might have collected the secretions. The authors also note that the morphology of the skull is also consistent with a venomous predator: the snout is narrow and the skull has a “tall later profile with a large gape,” suggesting that the dino had a relatively weak bite and therefore needed help from venom to incapacitate its prey.
They conclude that “Sinornithosaurus was a venomous predator that fed on birds by using its long fants to penetrate through the plumage and into the skin, and the toxins would induce shock and permit the victim to be subndued rapidly.” [Note: some have suggested that S. millenii might have been an ancestor of modern birds, but Gong et al. clearly disagree, since they envision birds as being its prey.]
The reason this paper was PNAS-worthy is because if the report is true, this would make S. millenii the first known venomous dinosaur, and of course dinosaurs are the ultimate charismatic macrofauna. Anything new about them is sure to get wide attention.
Ed Yong has a more detailed report at on Not Exactly Rocket Science , including statements from dissenters who argue that the evidence for venom use is less than airtight. Perhaps the authors should have been a bit more cautious in their title!
Fig. 1. Photograph of the holotype of S. millenii (IVPP V12811) showing dentition with venom grooves (vg). mxf, maxillary fang (from the paper).
Fig. 2. Sinornithosauris millenii. Illustration by Mick Ellison (from WEIT).
h/t: Ed Yong for the pdf.
Gong, E., L. D. Martin, D. A. Burnham, and A. R. Falk. 2009. The birdlike raptor Sinornithosauris was venomous. Proc Natl Acad Sci U S A early edition
(If you’re interested in punctuated equilibrium and cryptic species in marine microfossils, see also Hull, P. M., and R. D. Norris. 2009. Evidence for abrupt speciation in a classic case of gradual evolution. Proc Natl Acad Sci U S A 106:21224-21229.)