Well-preserved fossils of a feathered dinosaur that lived about 124 million years ago — along with certain aspects of its teeth and skull — suggest that the turkey-sized creature was venomous.

Sinornithosaurus was unearthed in China and first described by scientists about 10 years ago, but the telling details of the creature’s cranial anatomy are just now being reported, says David Burnham, a paleontologist at the University of Kansas in Lawrence.

Most of the teeth in each side of the creature’s upper jaw have grooves that run from the base of each tooth to the tip, a characteristic seen in some of today’s venomous reptiles. A large triangular depression on the creature’s upper jawbone — a feature not previously reported in other dinosaurs or their relatives — probably held venom-producing glands, Burnham and his colleagues report online December 21 in the Proceedings of the National Academy of Sciences. Venom flowing from those glands probably pooled in reservoirs at the base of each grooved tooth until the dino bit its prey, Burnham says.

A few of Sinornithosaurus’ narrow teeth were quite a bit longer than the others. Modern creatures that have a similar variability in tooth length typically bite and hold their prey, Burnham says. So, he and his colleagues speculate, Sinornithosaurus probably used its venom to quickly stun struggling victims, which probably included small-to-medium-sized birds, by sending them into shock.

Sinornithosaurus may have subdued its prey with venom that flowed into a victim through unique grooves in many of the dinosaur’s teeth, a new study suggests. Triangular depressions on the creature’s upper jaw (arrow) likely held venom-producing glands.Credit: National Academy of Sciences