Post by DinosaurMichael on Feb 28, 2012 8:59:58 GMT -5
Tarbosaurus - Tarbosaurus bataar
Tarbosaurus ( /ˌt¨»rbɵˈsɔrəs/ tar-bo-sawr-əs; meaning "alarming lizard") is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China. Although many species have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts contend that this species is actually an Asian representative of the North American genus Tyrannosaurus; if true, this would invalidate the genus Tarbosaurus altogether. Tarbosaurus and Tyrannosaurus are considered to be at least closely related genera, if not synonymous. Alioramus, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing more than a ton and equipped with dozens of large, sharp teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs. Tarbosaurus lived in a humid floodplain criss-crossed by river channels. In this environment, it was an apex predator at the top of the food chain, probably preying on other large dinosaurs like the hadrosaur Saurolophus or the sauropod Nemegtosaurus. Tarbosaurus is very well represented in the fossil record, known from dozens of specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure. Although smaller than Tyrannosaurus, Tarbosaurus was one of the largest tyrannosaurids. The largest known individuals were between 10 and 12 meters (30 to 40 ft) long. The mass of a fully grown individual is considered comparable to or slightly smaller than Tyrannosaurus. The largest known Tarbosaurus skull is more than 1.3 meters (4 ft) long, larger than all other tyrannosaurids except Tyrannosaurus. The skull was tall, like that of Tyrannosaurus, but not as wide, especially towards the rear. The unexpanded rear of the skull meant that Tarbosaurus eyes did not face directly forwards, suggesting that it lacked the binocular vision of Tyrannosaurus. Large fenestrae (openings) in the skull reduced its weight. Between 60 and 64 teeth lined its jaws, slightly more than in Tyrannosaurus but fewer than in smaller tyrannosaurids like Gorgosaurus and Alioramus. Most of its teeth were oval in cross section, although the teeth of the premaxilla at the tip of the upper jaw had a D-shaped cross section. This heterodonty is characteristic of the family. The longest teeth were in the maxilla (upper jaw bone), with crowns up to 85 millimeters (3.3 in) long. In the lower jaw, a ridge on the outer surface of the angular bone articulated with the rear of the dentary bone, creating a locking mechanism unique to Tarbosaurus and Alioramus. Other tyrannosaurids lacked this ridge and had more flexibility in the lower jaw. Tyrannosaurids varied little in body form, and Tarbosaurus was no exception. The head was supported by an S-shaped neck, while the rest of the vertebral column, including the long tail, was held horizontally. Tarbosaurus had tiny forelimbs, proportionably to body size the smallest of all members of the family. The hands had two clawed digits each, with an additional unclawed third metacarpal found in some specimens, similar to closely related genera. Holtz has suggested that Tarbosaurus also has a theropod reduction of fingers IV-I "developed further" than in other tyrannosaurids, as the second metacarpal in the Tarbosaurus specimens he studied is less than twice the length of the first metacarpal (other tyrannosaurids have a second metacarpal about twice the length of the first metacarpal). Also, the third metacarpal in Tarbosaurus is proportionally shorter than in other tyrannosaurids; in other tyrannosaurids (like Albertosaurus and Daspletosaurus), the third metacarpal is often longer than the first metacarpal, while in the Tarbosaurus specimens studied by Holtz, the third metacarpal is shorter than the first. In contrast to the forelimbs, the three-toed hindlimbs were long and thick, supporting the body in a bipedal posture. The long, heavy tail served as a counterweight to the head and torso and placed the center of gravity over the hips.
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.
Tarbosaurus ( /ˌt¨»rbɵˈsɔrəs/ tar-bo-sawr-əs; meaning "alarming lizard") is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China. Although many species have been named, modern paleontologists recognize only one, T. bataar, as valid. Some experts contend that this species is actually an Asian representative of the North American genus Tyrannosaurus; if true, this would invalidate the genus Tarbosaurus altogether. Tarbosaurus and Tyrannosaurus are considered to be at least closely related genera, if not synonymous. Alioramus, also from Mongolia, is thought by some authorities to be the closest relative of Tarbosaurus. Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing more than a ton and equipped with dozens of large, sharp teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs. Tarbosaurus lived in a humid floodplain criss-crossed by river channels. In this environment, it was an apex predator at the top of the food chain, probably preying on other large dinosaurs like the hadrosaur Saurolophus or the sauropod Nemegtosaurus. Tarbosaurus is very well represented in the fossil record, known from dozens of specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure. Although smaller than Tyrannosaurus, Tarbosaurus was one of the largest tyrannosaurids. The largest known individuals were between 10 and 12 meters (30 to 40 ft) long. The mass of a fully grown individual is considered comparable to or slightly smaller than Tyrannosaurus. The largest known Tarbosaurus skull is more than 1.3 meters (4 ft) long, larger than all other tyrannosaurids except Tyrannosaurus. The skull was tall, like that of Tyrannosaurus, but not as wide, especially towards the rear. The unexpanded rear of the skull meant that Tarbosaurus eyes did not face directly forwards, suggesting that it lacked the binocular vision of Tyrannosaurus. Large fenestrae (openings) in the skull reduced its weight. Between 60 and 64 teeth lined its jaws, slightly more than in Tyrannosaurus but fewer than in smaller tyrannosaurids like Gorgosaurus and Alioramus. Most of its teeth were oval in cross section, although the teeth of the premaxilla at the tip of the upper jaw had a D-shaped cross section. This heterodonty is characteristic of the family. The longest teeth were in the maxilla (upper jaw bone), with crowns up to 85 millimeters (3.3 in) long. In the lower jaw, a ridge on the outer surface of the angular bone articulated with the rear of the dentary bone, creating a locking mechanism unique to Tarbosaurus and Alioramus. Other tyrannosaurids lacked this ridge and had more flexibility in the lower jaw. Tyrannosaurids varied little in body form, and Tarbosaurus was no exception. The head was supported by an S-shaped neck, while the rest of the vertebral column, including the long tail, was held horizontally. Tarbosaurus had tiny forelimbs, proportionably to body size the smallest of all members of the family. The hands had two clawed digits each, with an additional unclawed third metacarpal found in some specimens, similar to closely related genera. Holtz has suggested that Tarbosaurus also has a theropod reduction of fingers IV-I "developed further" than in other tyrannosaurids, as the second metacarpal in the Tarbosaurus specimens he studied is less than twice the length of the first metacarpal (other tyrannosaurids have a second metacarpal about twice the length of the first metacarpal). Also, the third metacarpal in Tarbosaurus is proportionally shorter than in other tyrannosaurids; in other tyrannosaurids (like Albertosaurus and Daspletosaurus), the third metacarpal is often longer than the first metacarpal, while in the Tarbosaurus specimens studied by Holtz, the third metacarpal is shorter than the first. In contrast to the forelimbs, the three-toed hindlimbs were long and thick, supporting the body in a bipedal posture. The long, heavy tail served as a counterweight to the head and torso and placed the center of gravity over the hips.
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.
