Sinosauropteryx is a compsognathid dinosaur. Described in 1996, it was the first dinosaur taxon outside of Avialae (birds and their immediate relatives) to be found with evidence of feathers. It was covered with a coat of very simple filament-like feathers. Some contention has arisen with an alternative interpretation of the filamentous impression as remains of collagen fibres, but this has not been widely accepted. It was mentioned in the Ornitholestes entry in The Complete Guide To Prehistoric Life.
Sinosauropteryx was a small theropod with an unusually long tail and short arms. The longest known specimen reaches up to 1.07 m (3.5 ft) in length, with an estimated weight of 0.55 kg (1.2 lb). It was a close relative of the similar but older genus Compsognathus, both genera belonging to the family Compsognathidae. Only one species of Sinosauropteryx has been named: S. prima, meaning "first" in reference to its status as the first feathered non-avialian dinosaur species discovered. Three specimens have been described. The third specimen previously assigned to this genus represents either a second, as-yet unnamed species or a distinct, related genus.
Sinosauropteryx lived in what is now northeastern China during the early Cretaceous period. It was among the first dinosaurs discovered from the Yixian Formation in Liaoning Province, and was a member of Jehol Biota. Well-preserved fossils of this species illustrate many aspects of their biology, such as their diet and reproduction.