Sinornithosaurus
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Sinornithosaurus Temporal range: Early Cretaceous, 124.6–122 Ma |
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| S. millenii fossil, Hong Kong Science Museum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | Saurischia |
| Suborder: | Theropoda |
| Family: | †Dromaeosauridae |
| Clade: | †Microraptoria |
| Genus: |
†Sinornithosaurus Xu, Wang & Wu, 1999 |
| Type species | |
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†Sinornithosaurus millenii Xu, Wang, & Wu, 1999 |
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| Species | |
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Sinornithosaurus (derived from a combination of Latin and Greek, meaning 'Chinese bird-lizard') is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period (early Aptian) of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999. The original specimen was collected from the Sihetun locality of western Liaoning. It was found in the Jianshangou beds of the Yixian Formation, dated to 124.5 million years ago. Additional specimens have been found in the younger Dawangzhangzi bed, dating to around 122 million years ago.
Xu Xing described Sinornithosaurus and performed a phylogenetic analysis which demonstrated that it is basal, or primitive, among the dromaeosaurs. He has also demonstrated that features of the skull and shoulder are very similar to Archaeopteryx and other Avialae. Together these two facts demonstrate that the earliest dromaeosaurs were more like birds than the later dromaeosaurs were.
Sinornithosaurus was among the smallest dromaeosaurids, with a length of about 90 centimetres (3.0 ft). In 2010, Gregory S. Paul gave higher estimations of 1.2 metres and three kilogrammes.
Specimens of Sinornithosaurus have preserved impressions of feathers both covering the entirety of the body and forming the wings. These feathers were indistinguishable in form from those found on birds from the same geological deposits. The body (contour) feathers were generally between 3-4.5 cm long and included two types: the first type are formed of several filaments joined together into "tufts", similar to modern down feathers. The second type, including those on the arms, were composed of rows of filaments (barbs) joined together along a main shaft (rachis), making them similar in structure to modern bird feathers. However, unlike the wing feathers of flying birds, they did not have the secondary branches with tiny little hooks (barbules) that flight feathers have, which allow the flight feathers to form a continuous vane. Some scientists have suggested that the feathers might have allowed Sinornithosaurus to glide for short distances after leaping from trees.
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Wikipedia