Avimimus

The remains of Avimimus were recovered by Russian paleontologists and officially described by Dr. Sergei Kurzanov in 1981. The Avimimus fossils were initially described as having come from the Djadokta Formation by Kurzanov; however, in a 2006 description of a new specimen, Watabe and colleagues noted that Kurzanov was probably mistaken about the provenance, and it is more likely that Avimimus hailed from the more recent Nemegt Formation. The type species is A. portentosus. A variety of isolated bones that have been attributed to Avimimus were considered to be distinct from A. portentosus, and were initially referred to as Avimimus sp. In 2008, a team of Canadian, American, and Mongolian paleontologists headed by Phil Currie reported in 2006 an extensive bonebed of Avimimus sp. fossils. The bonebed is in the Nemegt Formation, 10.5 meters above the Barun Goyot Formation, in the Gobi Desert. The team reported finding abundant bones of at least ten individuals of Avimimus, but the deposit may hold more. All individuals were either adult or subadult, and the adults showed little variation in size, suggesting determinate growth. The team also suggests that the individuals were found together because they were gregarious in life, providing possible indications that Avimimus formed age-segregated groups for either lekking or flocking purposes. The adults showed a greater degree of skeletal fusion in the tarsometatarsus and tibiotarsus, and also more prominent muscle scars. The preservation of the bonebeds suggest that they were buried rapidly, uncovered by rapid flow of water, and then buried again a short distance away. In 2018, Avimimus sp. was formally described as a new species, A. nemegtensis. ==Description==

Avimimus was a small, bird-like dinosaur with a length of 1.5 m (5 ft). Kurzanov, in 1987, also reported the presence of quill knobs, and while Chiappe confirmed the presence of bumps on the ulna, their function remained unclear. Kurzanov was so convinced they were attachment points for feathers that he concluded that Avimimus may have been capable of weak flight. The presence of feathers is now widely accepted, but most paleontologists do not believe Avimimus could fly. The ilium was almost horizontally oriented, resulting in exceptionally broad hips. Little is known of the tail but the hip suggests that the tail was long. The legs were extremely long and slender, suggesting that Avimimus was a highly specialized runner. The proportions of the leg bones add further weight to the idea of Avimimus was quick on its feet. The animal's shins were long in comparison with its thighs, a trait common among cursorial animals. It also had three-toed feet with narrow pointed claws. ==Classification==

Avimimus was originally suggested to be a very close relative of birds, given its unique suite of bird-like features not known in other dinosaurs at the time. In fact, Kurzanov argued that Avimimus, rather than the famous early bird Archaeopteryx, was close to the direct ancestor of modern birds, and that Archaeopteryx was not as closely related to birds as had previously been suggested. Kurzanov placed Avimimus in its own family, Avimimidae, in 1981. In 1991, Sankar Chatterjee erected the Order Avimimiformes to include Avimimus. Neither of these group names is used frequently by paleontologists as they include only a single species. More recent studies have shown that Avimimus is best grouped within the Oviraptoridae, within the subgroup Elmisaurinae. The following cladogram follows an analysis by Phil Senter, 2007. ==Paleoecology==

of A. nemegtensis reported in 2006 The Nemegt Formation of Mongolia, is estimated to date back to the Maastrichtian. During the Late Cretaceous period, the land that is now the Nemegt Formation had a continental semi-arid climate, with average annual temperatures estimated at 7-8 Degrees C annually. It is interpreted as having wet summers and dry winters, with summer rainfall sourced from the East Asian monsoon. The Nemegt formation is characterized by a floodplain ecosystem, considered similar to the Okavango Delta today. In the Nemegt it coexisted with other dinosaurs like, the tyrannosaurid Tarbosaurus, hadrosaurid Saurolophus, and a variety of other dinosaurs. Both species of Avimimus come from different layers in the Nemegt formation. A. portentosus is known from the Bugiin Tsav and Shar Tsav localities, correlated to the Middle & Upper Nemegt formation. A. nemegtensis comes from the Nemegt locality, correlated with the Lower Nemegt formation. ==See also==