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SIE - nor - nith - oh - SAW - rus
Name Means: "Chinese bird lizard"
The small predatory dinosaur Sinornithosaurus was a dromaeosaurid-one of a group of agile bipedal runners with large eyes, relatively large brains, and long, narrow snouts equipped with steak-knife teeth. The three fingers on each hand and the four toes of each foot had long, curved, wickedly sharp claws for hooking into prey, with the second toe claw being extra large. As in many other dinosaurs, especially fast-running kinds, the tail was stiffened by overlapping bony rods.
While much smaller than its famous relatives Deinonychus and Velociraptor, Sinornithosaurus would have been an equally effective predator on a small scale. It may have been a solitary hunter of large insects, lizards, primitive birds, and small mammals, but it is also possible that groups of Sinornithosaurus cooperated to hunt and bring down small plant-eating dinosaurs and other prey bigger than themselves.
The only known skeleton of Sinornithosaurus was described in 1999 and is missing most of the vertebral column and rib cage, but the skull, shoulders, hips, and limb bones are well preserved. Many details of the skeleton are similar to those of the primtive bird Archaeopteryx, providing evidence that dromaeosaurids were the dinosaurs most closely related to birds. The forelimbs are about four-fifths as long as the hindlimbs, and the shoulder sockets face to the side, allowing a wide range of movement, as in Archaeopteryx. Although unable to fly, Sinornithosaurus might have been able to "flap" its arms and snatch small flying prey out of the air.
Another birdlike feature of Sinornithosaurus is a dense covering of downlike filaments over most of its body. Many other dinosaurs may have had these protofeathers, but only under exceptional geological conditions are they preserved during fossilization. Similar structures are found in four other kinds of small theropods from the same locality in Liaoning province, China.