MEXICO CITY--In one of the frightening scenes in the movie Jurassic Park, a creature called Dilophosaurus spits deadly wads of poison. However realistic that looked on the big screen, it's pure fantasy: There has been no hard fossil evidence that any dinosaur killed its prey with venom. But on 26 October, researchers here at the annual meeting of the Society of Vertebrate Paleontology unveiled a grooved tooth that may have been used for lethal injections.
Predators that kill with venom tend to have specialized teeth. The cobra, for example, has fangs like hypodermic needles; others use grooves to channel poisons to their mark. But very few such teeth have been found as fossils. A notable exception is an extinct relative of mammals (Euchambersia mirabilis) about 250 million years old that was found in South Africa. It had a deeply grooved tooth and an opening in its skull for what looks like venom glands. Also impressive is an archosaurian reptile (Uatchitodon kroehleri) from the late Triassic that had a fanglike tooth.
Now dinosaurs may be added to the list. Paleontologist Ruben Rodriguez-de la Rosa of the Museo del Desierto in Saltillo, Mexico, was studying a collection of fossil teeth from the Baja peninsula when he noticed a 2-centimeter-long broken tooth that dates to the late Cretaceous. In some aspects, it resembles the teeth of a Velociraptor-like dinosaur called Saurornitholestes. But unlike teeth of other theropods--the group of bipedal carnivores that includes velociraptors and tyrannosaurs--its edge doesn't have serrations; instead, a unique groove runs almost the length of the tooth. This feature "agrees with what is thought to be a venom groove," say Rodriguez-de la Rosa and his colleague Francisco Aranda-Manteca of the Universidad Autónoma de Baja California in Ensenada.
Groovy, yes, but not everyone is convinced about the venom. "It's possible," says Hans-Dieter Sues, a paleontologist at the Royal Ontario Museum in Toronto. But he thinks it's more likely that the groove held decaying food, in which pathogenic bacteria thrived. That way, the groove may have helped to ensure a septic bite that sickened its victims if it didn't kill them right away--a tactic still used by Komodo dragons.