Scientists are analysing fossils of a 200 million-year-old reptile of the late Triassic period to understand how syringe-like teeth evolved in snakes that exist today.
Although not closely related to snakes, Uatchitodon’s hollow fangs suggest it was venomous.
The roots of its teeth suggest that the animal is more closely related to dinosaurs and alligators than to modern snakes, but the ‘hypodermic needle’ structures found in many specimens are remarkably similar to snake fangs and probably followed a similar evolutionary path.
Uatchitodon fossils are found at three major locations: Tomahawk in Virginia, Moncure in North Carolina and the Placerias Quarry in Arizona.
Jonathan Mitchell at the University of Chicago in Illinois, and his colleagues analysed Uatchitodon teeth and found that the fossils from Tomahawk had grooves instead of fully developed tubes.
In the oldest fossils from Tomahawk, the venom canal was a shallow groove, extending from the base of the tooth less than a quarter of the way to the tip. Later teeth from the site had a longer and deeper groove.
In specimens from Moncure and the Placerias Quarry, the groove had become all but sealed in, with just a hair-like seam to mark it, creating a canal that could convey venom once the tooth had pierced the skin – suggesting that the tubes in the teeth of Uatchitodon had evolved from grooves.
The progression seen in the Uatchitodon teeth is very similar to the development of snake replacement fangs, in which early-stage fangs form a groove, and late-stage fangs are tubular.
“This fossil really suggests that you can’t get hollow fangs any other way,” Nature quoted herpetologist Wolfgang Wuster at Bangor University, UK, as saying.
According to him, this progression makes sense because Gila-style grooved teeth would benefit animals even in the initial evolutionary stages. For alternative possible methods of producing a fang, such as boring a tube straight through a tooth, this would not be the case.
However, Wuster said that finding Uatchitodon jaws would be important to check whether specimens with hollow fangs – but not those with grooved teeth – had compressor muscles that could squirt venom into prey.
“A syringe without a plunger is pretty useless, so I’d love to get a look at the jaws.”
The research is reported in the journal Naturwissenschaften.