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. 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. However, in 2010, another team of scientists led by Federico Gianechini published a paper casting doubts on the claim that Sinornithosaurus was venomous. They noted that grooved teeth are not unique to this genus, and in fact grooved teeth are found in many other theropods, including other dromaeosaurids. They also demonstrated that the teeth were not abnormally long as Gong and his team claimed, but rather had come out of their sockets, a preservational artifact common in crushed and flattened fossils. Finally, they could not independently verify the presence of supposed chambers for venom glands cited by Gong's team, finding only the normal sinuses of the skull. In the same journal issue, Gong and his team submitted a reassessment of the 2009 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. However, these grooved teeth are not direct evidence of venom, as non-venomous species of animals (such as baboons) have similarly grooved teeth. Circadian rhythm Comparisons between the scleral rings of Sinornithosaurus and modern birds and reptiles indicate that it may have been cathemeral, active throughout the day and night at short intervals. Flight/gliding The possibility that Sinornithosaurus was capable of gliding has been presented several times, due to