Sinosauropteryx ("Chinese lizard-wing") is the first and most primitive dinosaur found with the fossilized impressions of feathers. It lived in China during the early Cretaceous period and may have been a close relative of Compsognathus. The largest known specimens are 1-1.20 meters (3 ft) in length, most of which was taken up by its extremely long tail. The remarkably well-preserved fossils show that Sinosauropteryx was covered with a furry down of very simple feathers. These feathers consisted of a simple two-branched structure, similar to the secondarily primitive feathers of the modern kiwi.

Taxonomy

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Sinosauropteryx is important because it had feather-like structures, yet was not very closely related to the previous "first bird" Archaeopteryx. There are many dinosaur families that were more closely related to Archaeopteryx than Sinosauropteryx was, including the deinonychosaurs, the oviraptosaurs and therizinosaurs. This indicates that feathers may have been a characteristic of many theropod dinosaurs, not just the obviously bird-like ones, making it possible that equally distant animals such as Ornitholestes, Coelurus, and Compsognathus had feathers as well, although their close proximity to the origin of feathers and the presence of scales on Juravenator and Tyrannosaurus make the distribution of feathers in primitive coelurosaurs extremely difficult to estimate accurately.

Most paleontologists do not consider Sinosauropteryx to be a bird, because phylogenetically, it lies far from the clade Aves, usually defined as Archaeopteryx + modern birds. The scientists who discovered and described Sinosauropteryx, however, use the traditional Linnean definition of the Class Aves, that is, any animal with feathers is a bird. They argue that the filamentous plumes of Sinosauropteryx represent true feathers with a rachis and barbs, and therefore that Sinosauropteryx should be considered a true bird (Ji & Ji, 1997). They classify it in a new biological order, Sinosauropterygiformes, family Sinosauropterygidae (Ji & Ji, 1996).

Diet

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One specimen of Sinosauropteryx (GMV 2124) was found with several mammal jaws in its stomach region. Hurum, Luo & Kielan-Jaworowska (2006) identified these jaws as belonging to the species Zhangheotherium and Sinobaatar, showing that these two mammals were part the Sinosauropteryx diet. Interestingly, Zhangheotherium is known to have had a poisonous spur, like the modern platypus, showing that Sinosauropteryx fed on possibly poisonous mammals.

References

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• Chen, P., Dong, Z., Zhen, S. (1998). "An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China." Nature, 391, 147-152.
• Hurum, J. O., Z.-x. Luo, & Z. Kielan-Jaworowska (2006). "Were mammals originally venomous?" Acta Palaeontologica Polonica 51(1):1–11.
• Ji, Q. and Ji, S. (1996). "On discovery of the earliest bird fossil in China and the origin of birds." Chinese Geology 10 (233): 30-33.
• Ji, Q. and Ji, S. (1997). "Advances in Sinosauropteryx Research." Chinese Geology, 7: 30-32.

Cretaceous dinosaurs | Asian dinosaurs | Coelurosaurs | Feathered dinosaurs

Sinosauropteryx | Sinosauropteryx | Sinosauropteryx | シノサウロプテリクス | Sinosauropteryx