Overview of Sinornithosaurus

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Updated on October 28, 2019

Of all the dino-bird fossils discovered in the Liaoning Quarry in China, Sinornithosaurus may be the most famous, because it's the most complete: the perfectly preserved skeleton of this early Cretaceous dinosaur shows evidence not only of feathers but of different kinds of feathers on different parts of its body. The feathers on this small theropod's head were short and hairlike, but the feathers on its arms and tail were long and distinctively birdlike, with tufts of intermediate length along its back. Technically, Sinornithosaurus is classified as a raptor, on the basis of the single, oversized, sickle-shaped single claws on each of its hind feet, which it used to tear at and disembowel prey; on the whole, though, it bears a greater resemblance to the other dino-birds of the Mesozoic Era (like Archaeopteryx and Incisivosaurus) than it does to famous raptors like Deinonychus and Velociraptor.

At the end of 2009, a team of paleontologists generated headlines by claiming Sinornithosaurus to be the first identified venomous dinosaur (never mind that poison-spitting Dilophosaurus you saw in Jurassic Park, which was based on fantasy rather than fact). The supposed evidence in favor of this behavior: fossilized pouches connected by ducts to this dinosaur's snake-like fangs. At the time, reasoning by analogy with modern animals, it would have been surprising if these sacs weren't exactly what they appeared to be--repositories of venom that Sinornithosaurus used to immobilize (or kill) its prey. However, a more recent, and more convincing, study has concluded that the supposed "pouches" of Sinornithosaurus were created when this individual's incisors loosened from their sockets, and aren't evidence of a venomous lifestyle after all!