|Home time period||Early Cretaceous|
|Creature type||Theropod dinosaur|
Sinornithosaurus was a gliding feathered dinosaur.[118-97]
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 been allowed Sinornithosaurus to glide for short distances after leaping from trees.
A 2010 study indicated that Sinornithosaurus may have had feathers which varied in color significantly across different regions of the body, based on analysis of microscopic cell structures in preserved fossils. A later study in 2012 showed that the colours of Sinornithosaurus were reddish-brown, yellow, black and grey, which were spread around its body.
In 2009, a team of scientists led by Empu Gong examined a well-preserved Sinornithosaurus skull, and noted several features suggesting it was the first-identified venomous dinosaur. Gong and colleagues noted that the unusually long and fang-like mid-jaw (maxillary) teeth had prominent grooves running down the outer surface, towards the rear of the tooth, a feature seen only in venomous animals. They also interpreted a cavity in the jaw bone just above these teeth as the possible site for the soft-tissue venom gland. This is now known to be false, as the site for a venom gland does not exist, and the teeth are long just because they are slightly loosened from the skull. Gong and colleagues suggested that these unique features indicated that Sinornithosaurus may have specialized in hunting small prey such as birds, using its long fangs to penetrate feathers and envenomate and stun the prey, like a modern snake. They also suggested that the short, slightly forward-pointing teeth at the tip of the jaw could have been used to strip feathers from birds. Sinornithesaurus used its big body to attack large gliding prey such as the microraptor which is seen in the episode.
It appears on the episode Feathered Dragons and is seen hunting a Microraptor, which it then attacks, giving the Xianglong a chance to escape. The Microraptor realizes that it has been turned from predator to prey and manages to glide, with the Sinornithosaurus in hot pursuit. Then when the Microraptor lands below the former on the next tree, both it and the Sinornithosaurus land on the ground. Once on the ground, the Microraptor heads for the next tree, but hops instead. The Sinornithosaurus, however, has no difficulty in running across the ground. The Microraptor then climbs the tree it was heading for, then lands on a branch before taking off, with the Sinornithosaurus looking on as its quarry glides off.
John Hurt says that Sinornithosaurus and Sinosauropteryx have revealed a big mystery - the colors. Through the pigment on the fossils, it was found that Sinosauropteryx was reddish orange with a series of white stripes along it's tail. Sinornithosaurus had reddish brown, yellow, gray and black feathers- perfect for camouflage. Later, a pack of Sinornithosaurus manage kill a mother Jeholosaurus by biting their venomous teeth into her neck, front foot and back leg.
- Sinornithosaurus may not have been venomous. The elongated teeth were actually loose and the venom grooves are actually the same as other theropods. So this hypothesis may have been based on a badly preserved skull. However, in the same journal issue, Gong and his team submitted a reassessment of the 2010 study, casting doubt on their findings. They admitted that grooved teeth were common among theropods (though they suggested they were really only prevalent among feathered maniraptorans), and hypothesized that venom may have been a primitive trait for all archosaurs if not all reptiles, which was retained in certain lineages. They also disputed the claim that the teeth were significantly out of their sockets in the holotype specimen of Sinornithosaurus, though they admitted that they were not in a completely natural position. Gong's reassessment also claimed that certain undescribed specimens had fully articulated teeth showing a similar length. So it may have been venomous after all. But it is still debated.
- John Hurt, the narrator of Planet Dinosaur, said that he had difficulty in pronouncing the creature's name.
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