A SET of 200-million-year-old teeth from a beast related to dinosaurs and crocodiles has shed light on how snake fangs evolved. They support the idea that venom canals inside fangs evolved from grooves on the tooth surface.

The late Triassic reptile Uatchitodon is known only from its teeth, which resemble tall, serrated crocodile or dinosaur teeth. Several have been found, and the two youngest ones, dating from 220 million years ago, have what look like venom canals. An older set have grooves of different depths but no canals. Until now it was unknown whether the variations reflected evolutionary changes, different stages of tooth development, or even teeth from different positions in the mouth.