|
''Daspletosaurus'' ( ; meaning "frightful lizard") is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species (''D. torosus'') were found in Alberta, although other possible species from Alberta and Montana await description. Including these undescribed species makes ''Daspletosaurus'' the most species-rich genus of tyrannosaur. ''Daspletosaurus'' is closely related to the much larger and more recent ''Tyrannosaurus''. Like most known tyrannosaurids, it was a multi-tonne bipedal predator equipped with dozens of large, sharp teeth. ''Daspletosaurus'' had the small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera. As an apex predator, ''Daspletosaurus'' was at the top of the food chain, probably preying on large dinosaurs like the ceratopsid ''Centrosaurus'' and the hadrosaur ''Hypacrosaurus''. In some areas, ''Daspletosaurus'' coexisted with another tyrannosaurid, ''Gorgosaurus'', though there is some evidence of niche differentiation between the two. While ''Daspletosaurus'' fossils are rarer than other tyrannosaurids', the available specimens allow some analysis of the biology of these animals, including social behavior, diet and life history. == Description == While very large by the standard of modern predators, ''Daspletosaurus'' was not the largest tyrannosaurid. Adults could reach a length of 8–9 meters (26–30 ft) from snout to tail. Mass estimates have centered around 2.5 tonnes (2.75 short tons)〔 but have ranged between 1.8 and 3.8 tonnes (2.0 and 4.1 short tons). ''Daspletosaurus'' had a massive skull that could reach more than 1 meter (3.3 ft) in length.〔 The bones were heavily constructed and some, including the nasal bones on top of the snout, were fused for strength. Large fenestrae (openings) in the skull reduced its weight. An adult ''Daspletosaurus'' was armed with about six dozen teeth that were very long but oval in cross section rather than blade-like. Unlike its other teeth, those in the premaxilla at the end of the upper jaw had a ''D''-shaped cross section, an example of heterodonty always seen in tyrannosaurids. Unique skull features included the rough outer surface of the maxilla (upper jaw bone) and the pronounced crests around the eyes on the lacrimal, postorbital, and jugal bones. The orbit (eye socket) was a tall oval, somewhere in between the circular shape seen in ''Gorgosaurus'' and the 'keyhole' shape of ''Tyrannosaurus''. Split carinae〔http://www.geology.cz/bulletin/fulltext/bullgeosci200803351.pdf〕 have been found on ''Daspletosaurus'' teeth. ''Daspletosaurus'' shared the same body form as other tyrannosaurids, with a short, ''S''-shaped neck supporting the massive skull. It walked on its two thick hindlimbs, which ended in four-toed feet, although the first digit (the hallux) did not contact the ground. In contrast, the forelimbs were extremely small and bore only two digits, although ''Daspletosaurus'' had the longest forelimbs in proportion to body size of any tyrannosaurid. A long, heavy tail served as a counterweight to the head and torso, with the center of gravity over the hips.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Daspletosaurus」の詳細全文を読む スポンサード リンク
|