Post by DinosaurMichael on Mar 28, 2012 7:06:06 GMT -5
Megatherium - Megatherium americanum
Megatherium ("Great Beast") was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately 5.3 million years. Its size was exceeded by only a few other land mammals, including mammoths and the even larger Paraceratherium. The rhinoceros-sized Promegatherium is suggested to be the ancestor of Megatherium. Megatherium was one of the largest mammals known, weighing up to eight tons, about as much as an African bull elephant. Although it was primarily a quadruped, its footprints show that it was capable of assuming a bipedal stance. When it stood on its hind legs it was about twenty feet (6 m) tall, twice the height of an elephant. This sloth, like a modern anteater, walked on the sides of its feet because its claws prevented it from putting them flat on the ground. Megatherium species were members of the abundant Pleistocene megafauna, large mammals that lived during the Pleistocene epoch. Megatherium had a robust skeleton with a large pelvic girdle and a broad muscular tail. Its large size enabled it to feed at heights unreachable by other contemporary herbivores. Rising on its powerful hind legs and using its tail to form a tripod, Megatherium could support its massive body weight while using the curved claws on its long forelegs to pull down branches with the choicest leaves. Its jaw is believed to have housed a long tongue, which it would then use to pull leaves into its mouth, similar to the modern tree sloth. Some recent morpho-functional analysis indicates that M. americanum was adapted for strong vertical biting. The teeth are hypsodont and bilophodont, and the sagittal section of each loph is triangular with a sharp edge. This suggests the teeth were used for cutting, rather than grinding, and that hard fibrous food was not the primary dietary component. Megatherium americanum skeleton, Muséum national d'Histoire naturelle, ParisRichard Fariña and Ernesto Blanco of the Universidad de la República in Montevideo have analysed a fossil skeleton of M. americanum and discovered that its olecranon - the part of the elbow to which the triceps muscle attaches - was very short. This adaptation is found in carnivores and optimises speed rather than strength. The researchers say this would have enabled M. americanum to use its claws like daggers. They suggest that to add nutrients to its diet, Megatherium may have taken over the kills of Smilodon. Based on the estimated strength and mechanical advantage of its biceps, it has been proposed that Megatherium could have overturned adult glyptodonts (large, armored xenarthrans, related to armadillos) as a means of scavenging or hunting these animals. However, other zoologists have described this proposal as "fanciful".
Tyrannosaurus Rex
Tyrannosaurus ( /tɨˌrænɵˈsɔrəs/ or /taɪˌrænɵˈsɔrəs/; meaning "tyrant lizard", from Greek tyrannos (τύραννος) meaning "tyrant," and sauros (σαῦρος) meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, at the time an island continent termed Laramidia, with a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 67 to 65.5 million years ago. It was among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event. Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to 12.8 m (42 ft) in length, up to 4 metres (13 ft) tall at the hips, and up to 6.8 metric tons (7.5 short tons) in weight. By far the largest carnivore in its environment, Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger. The debate over Tyrannosaurus as apex predator or scavenger is among the longest running in paleontology. More than 30 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of Tyrannosaurus rex are a few subjects of debate. Its taxonomy is also controversial, with some scientists considering Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.
Megatherium ("Great Beast") was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately 5.3 million years. Its size was exceeded by only a few other land mammals, including mammoths and the even larger Paraceratherium. The rhinoceros-sized Promegatherium is suggested to be the ancestor of Megatherium. Megatherium was one of the largest mammals known, weighing up to eight tons, about as much as an African bull elephant. Although it was primarily a quadruped, its footprints show that it was capable of assuming a bipedal stance. When it stood on its hind legs it was about twenty feet (6 m) tall, twice the height of an elephant. This sloth, like a modern anteater, walked on the sides of its feet because its claws prevented it from putting them flat on the ground. Megatherium species were members of the abundant Pleistocene megafauna, large mammals that lived during the Pleistocene epoch. Megatherium had a robust skeleton with a large pelvic girdle and a broad muscular tail. Its large size enabled it to feed at heights unreachable by other contemporary herbivores. Rising on its powerful hind legs and using its tail to form a tripod, Megatherium could support its massive body weight while using the curved claws on its long forelegs to pull down branches with the choicest leaves. Its jaw is believed to have housed a long tongue, which it would then use to pull leaves into its mouth, similar to the modern tree sloth. Some recent morpho-functional analysis indicates that M. americanum was adapted for strong vertical biting. The teeth are hypsodont and bilophodont, and the sagittal section of each loph is triangular with a sharp edge. This suggests the teeth were used for cutting, rather than grinding, and that hard fibrous food was not the primary dietary component. Megatherium americanum skeleton, Muséum national d'Histoire naturelle, ParisRichard Fariña and Ernesto Blanco of the Universidad de la República in Montevideo have analysed a fossil skeleton of M. americanum and discovered that its olecranon - the part of the elbow to which the triceps muscle attaches - was very short. This adaptation is found in carnivores and optimises speed rather than strength. The researchers say this would have enabled M. americanum to use its claws like daggers. They suggest that to add nutrients to its diet, Megatherium may have taken over the kills of Smilodon. Based on the estimated strength and mechanical advantage of its biceps, it has been proposed that Megatherium could have overturned adult glyptodonts (large, armored xenarthrans, related to armadillos) as a means of scavenging or hunting these animals. However, other zoologists have described this proposal as "fanciful".
Tyrannosaurus Rex
Tyrannosaurus ( /tɨˌrænɵˈsɔrəs/ or /taɪˌrænɵˈsɔrəs/; meaning "tyrant lizard", from Greek tyrannos (τύραννος) meaning "tyrant," and sauros (σαῦρος) meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, at the time an island continent termed Laramidia, with a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 67 to 65.5 million years ago. It was among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event. Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to 12.8 m (42 ft) in length, up to 4 metres (13 ft) tall at the hips, and up to 6.8 metric tons (7.5 short tons) in weight. By far the largest carnivore in its environment, Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger. The debate over Tyrannosaurus as apex predator or scavenger is among the longest running in paleontology. More than 30 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of Tyrannosaurus rex are a few subjects of debate. Its taxonomy is also controversial, with some scientists considering Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.