Sinosauropteryx

Chapter • Meet the dinosaur

Overview

Sinosauropteryx was a small, slender predatory dinosaur roughly the size of a house cat once its tail is included. Specimens range from about 0.68 metres to just over a metre long, and nearly half of that was an exceptionally long tail containing more vertebrae than in any other known compsognathid. The arms were short and powerfully built with three fingers, the thumb bearing an unusually large claw, while the hind limbs were long and clearly built for quick, agile running. Its body was covered in short, hair-like filaments — often called protofeathers — forming a dense fringe along the neck, back and tail. These structures could not be used for flight and most likely served as insulation and for visual display. Because the fossils are so exceptionally preserved, researchers have been able to reconstruct the animal's colours. A 2010 study of melanosomes — microscopic pigment granules inside the filaments — showed that Sinosauropteryx was reddish-brown to ginger above with a much paler underside, and that its tail carried alternating dark and light bands. A later study revealed a dark facial mask across the eyes, rather like a raccoon or a shrike. The sharp boundary between dark back and pale belly points to a life in open, brightly lit habitats rather than deep, shaded forest. Sinosauropteryx was an active little hunter. Two specimens preserve gut contents: one contains jaws of small mammals belonging to the genera Zhangheotherium and Sinobaatar, and the other an almost complete lizard, Dalinghosaurus. Its menu therefore included lizards, small mammals and very probably insects, with the long tail working as a counterbalance during sharp turns in pursuit. One specimen also preserves two small eggs in the abdomen, showing that the female carried a pair of eggs at a time and had two functioning oviducts — a condition halfway between crocodilians and modern birds. The first specimen was found in 1996 by the farmer Li Yumin in the Yixian Formation of Liaoning, north-eastern China, and was described the same year by Ji Qiang and Ji Shu-An. The discovery caused a worldwide sensation: for the first time a non-avian dinosaur had been found with preserved feather-like structures, powerful evidence that birds descend from theropod dinosaurs. Sinosauropteryx opened the floodgates for the stream of feathered fossils from the Jehol Biota and permanently changed how we picture dinosaurs.

Chapter • Where it lived

Habitat

Sinosauropteryx lived around 125–122 million years ago in the Early Cretaceous, in what is now Liaoning Province in north-eastern China. Every known specimen comes from the Yixian Formation, chiefly the Jianshangou and Dawangzhangzi beds that form part of the celebrated Jehol Biota. The landscape was one of lakes, rivers and wooded plains under a temperate to cool climate, repeatedly blanketed by fine volcanic ash that buried animals and plants so quickly that skin, filaments and even stomach contents survived. Its colour pattern suggests Sinosauropteryx itself favoured the more open, sunlit parts of that landscape rather than closed forest canopy.

Chapter • Family life

Breeding

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy