Post by DinosaurMichael on Jan 10, 2012 8:34:26 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.
Steppe Rhinoceros - Elasmotherium sibiricum
Elasmotherium ("Thin Plate Beast") is an extinct genus of giant rhinoceros endemic to Eurasia during the Late Pliocene through the Pleistocene, documented from 2.6 mya to as late as 50,000 years ago, possibly later, in the Late Pleistocene, an approximate span of slightly less than 2.6 million years. Three species are recognised. The best known, E. sibiricum was the size of a mammoth and is thought to have borne a large, thick horn on its forehead which was used for defense, attracting mates, driving away competitors, sweeping snow from the grass in winter and digging for water and plant roots. Like all rhinoceroses, elasmotheres were herbivorous. Unlike any others, its high-crowned molars were ever-growing. Its legs were longer than those of other rhinos and were designed for galloping, giving it a horse-like gait. The Russian paleontologists of the 19th century who discovered and named the initial fossils were influenced by ancient legends of a huge unicorn roaming the steppes of Siberia. To date no evidence either contradicts or confirms the possibility that Elasmotherium survived into legendary times. The most reconstructed species is perhaps E. sibiricum by generations of scientists working at the Paleontological Museum in Moscow and elsewhere in Russia. The majority of the fossils fall or have fallen within their national jurisdiction. The dimensions and morphology of the various reconstructions vary considerably. They are for the most part estimating the gross details from the minutiae. However, they all agree on the general order of magnitude, that sibiricum was comparable to a Mammoth and was rather larger than the contemporary Woolly Rhinoceros. E. sibiricum had a measured shoulder height of approximately 2 metres (6.6 ft). To it, however, must be added the height of a massive hump anchored on the fin-like transverse processes extending from the top of the cervical vertebrae, a maximum of 53 centimetres (1.74 ft). The total height then was in excess of 253 centimetres (8.30 ft). The measured length of sibiricum (from a nearly complete skeleton found at Gaevskaya) is 4.5 metres (15 ft). Extrapolation from the greater size of caucasicum molars obtains a length of 5 metres (16 ft)¡ª5.2 metres (17 ft) for caucasicum. According to Legendre's formula, E. sibiricum had a mass of over 4,000 kilograms (3.9 long tons; 4.4 short tons); E. caucasicum, 5,000 kilograms (4.9 long tons; 5.5 short tons). These weights place Elasmotherium in the "really huge" category of all Rhinocerotidae and therefore the animal was "strongly brachyopodial;" that is, they required feet of large contact area to prevent sinking into the soil. The feet were unguligrade, the front larger than the rear: purely tridactyl on Digits II-IV in the rear, but with an extra vestigial digit, I, in the front.
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.
Steppe Rhinoceros - Elasmotherium sibiricum
Elasmotherium ("Thin Plate Beast") is an extinct genus of giant rhinoceros endemic to Eurasia during the Late Pliocene through the Pleistocene, documented from 2.6 mya to as late as 50,000 years ago, possibly later, in the Late Pleistocene, an approximate span of slightly less than 2.6 million years. Three species are recognised. The best known, E. sibiricum was the size of a mammoth and is thought to have borne a large, thick horn on its forehead which was used for defense, attracting mates, driving away competitors, sweeping snow from the grass in winter and digging for water and plant roots. Like all rhinoceroses, elasmotheres were herbivorous. Unlike any others, its high-crowned molars were ever-growing. Its legs were longer than those of other rhinos and were designed for galloping, giving it a horse-like gait. The Russian paleontologists of the 19th century who discovered and named the initial fossils were influenced by ancient legends of a huge unicorn roaming the steppes of Siberia. To date no evidence either contradicts or confirms the possibility that Elasmotherium survived into legendary times. The most reconstructed species is perhaps E. sibiricum by generations of scientists working at the Paleontological Museum in Moscow and elsewhere in Russia. The majority of the fossils fall or have fallen within their national jurisdiction. The dimensions and morphology of the various reconstructions vary considerably. They are for the most part estimating the gross details from the minutiae. However, they all agree on the general order of magnitude, that sibiricum was comparable to a Mammoth and was rather larger than the contemporary Woolly Rhinoceros. E. sibiricum had a measured shoulder height of approximately 2 metres (6.6 ft). To it, however, must be added the height of a massive hump anchored on the fin-like transverse processes extending from the top of the cervical vertebrae, a maximum of 53 centimetres (1.74 ft). The total height then was in excess of 253 centimetres (8.30 ft). The measured length of sibiricum (from a nearly complete skeleton found at Gaevskaya) is 4.5 metres (15 ft). Extrapolation from the greater size of caucasicum molars obtains a length of 5 metres (16 ft)¡ª5.2 metres (17 ft) for caucasicum. According to Legendre's formula, E. sibiricum had a mass of over 4,000 kilograms (3.9 long tons; 4.4 short tons); E. caucasicum, 5,000 kilograms (4.9 long tons; 5.5 short tons). These weights place Elasmotherium in the "really huge" category of all Rhinocerotidae and therefore the animal was "strongly brachyopodial;" that is, they required feet of large contact area to prevent sinking into the soil. The feet were unguligrade, the front larger than the rear: purely tridactyl on Digits II-IV in the rear, but with an extra vestigial digit, I, in the front.