Post by DinosaurMichael on Jan 13, 2012 17:55:19 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".
Therizinosaurus - Therizinosaurus cheloniformis
Therizinosaurus ( /θɛˌrɪzɨnɵˈsɔrəs/; 'scythe lizard', from the Greek therizo meaning 'to reap' or 'to cut off' and sauros meaning 'lizard') is a genus of very large theropod dinosaur. Therizinosaurus lived in the late Cretaceous Period (late Campanian-early Maastrichtian stages, around 70 million years ago), and was one of the last and largest representatives of its unique group, the Therizinosauria. Its fossils were first discovered in Mongolia and they were originally thought to belong to a turtle-like reptile (hence the species name, T. cheloniformis — "turtle-formed"). It is known only from a few bones, including gigantic hand claws, from which it gets its name. Though the fossil remains of Therizinosaurus are incomplete, inferences can be made about its physical characteristics based on related therizinosaurids. Like other members of its family, Therizinosaurus probably had a small skull atop a long neck, and had a bipedal gait and a heavy, deep, broad body (as evidenced by the wide pelvis of other therizinosaurids). Its forelimbs may have reached a length of 2.5 metres (8 feet) or even 3.5 metres for the largest known specimen. Its hindlimbs ended in four weight-bearing toes, unlike other theropod groups, in which the first toe was reduced to a dewclaw. Gregory S. Paul in 2010 estimated the length of Therizinosaurus at ten metres, the weight at five tonnes. It is the largest therizinosaur known and the largest known member of the Maniraptora. The most distinctive feature of Therizinosaurus was the presence of three gigantic claws on each digit of its frontlimbs. These were common among therizinosaurs but especially large in Therizinosaurus, and while the largest claw specimens are incomplete, they probably reached just under 1 metre (3.28 ft) in length. The claws are the longest known from any animal. The claws were relatively straight, only gradually tapering into a point, and extremely narrow, transversely flattened. The feeding habits of Therizinosaurus are unknown, since no skull material has ever been found that could indicate its diet. However, like other therizinosaurs, it was probably primarily herbivorous.
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".
Therizinosaurus - Therizinosaurus cheloniformis
Therizinosaurus ( /θɛˌrɪzɨnɵˈsɔrəs/; 'scythe lizard', from the Greek therizo meaning 'to reap' or 'to cut off' and sauros meaning 'lizard') is a genus of very large theropod dinosaur. Therizinosaurus lived in the late Cretaceous Period (late Campanian-early Maastrichtian stages, around 70 million years ago), and was one of the last and largest representatives of its unique group, the Therizinosauria. Its fossils were first discovered in Mongolia and they were originally thought to belong to a turtle-like reptile (hence the species name, T. cheloniformis — "turtle-formed"). It is known only from a few bones, including gigantic hand claws, from which it gets its name. Though the fossil remains of Therizinosaurus are incomplete, inferences can be made about its physical characteristics based on related therizinosaurids. Like other members of its family, Therizinosaurus probably had a small skull atop a long neck, and had a bipedal gait and a heavy, deep, broad body (as evidenced by the wide pelvis of other therizinosaurids). Its forelimbs may have reached a length of 2.5 metres (8 feet) or even 3.5 metres for the largest known specimen. Its hindlimbs ended in four weight-bearing toes, unlike other theropod groups, in which the first toe was reduced to a dewclaw. Gregory S. Paul in 2010 estimated the length of Therizinosaurus at ten metres, the weight at five tonnes. It is the largest therizinosaur known and the largest known member of the Maniraptora. The most distinctive feature of Therizinosaurus was the presence of three gigantic claws on each digit of its frontlimbs. These were common among therizinosaurs but especially large in Therizinosaurus, and while the largest claw specimens are incomplete, they probably reached just under 1 metre (3.28 ft) in length. The claws are the longest known from any animal. The claws were relatively straight, only gradually tapering into a point, and extremely narrow, transversely flattened. The feeding habits of Therizinosaurus are unknown, since no skull material has ever been found that could indicate its diet. However, like other therizinosaurs, it was probably primarily herbivorous.
