Sinornithosaurus

Sinornithosaurus (meaning "Chinese bird-lizard") is a small feathered dromaeosaurid (or, more commonly, 'raptor') and an early distant cousin of the birds.

In 2009, a team of Chinese palaeontologists lead by Enpu Gong examined a well-preserved Sinornithosaurus skull, and noted several features suggesting it may be the first-identified venomous dinosaur. Gong and his colleagues noted that the unusually long and fang-like mid-jaw teeth had prominent grooves running down the outer surface, towards the rear of the tooth, a feature seen only in venomous animals. They also interpreted that triangular depressions on the creature’s upper jaw (arrow) might have held the venom-producing glands.

Dr. Philip Currie, who has done a lot of work on feathered dinosaurs, says that the combination of long, grooved teeth and pits on the upper jaw does "suggest the possibility of a poison delivery system, but it may be very difficult to prove unequivocally in the absence of soft anatomy".