Post by DinosaurMichael on Mar 5, 2012 12:41:11 GMT -5
Ceratosaurus - Ceratosaurus nasicornis
Ceratosaurus ( /ˌsɛrətɵˈsɔrəs/) meaning "horned lizard", in reference to the horn on its nose (Greek κερας/κερατος, keras/keratos meaning "horn" and σαυρος/sauros meaning "lizard"), was a large predatory theropod dinosaur from the Late Jurassic Period (Kimmeridgian to Tithonian), found in the Morrison Formation of North America, in Tanzania and Portugal. It was characterized by large jaws with blade-like teeth, a large, blade-like horn on the snout and a pair of hornlets over the eyes. The forelimbs were powerfully built but very short. The bones of the sacrum were fused (synsacrum) and the pelvic bones were fused together and to this structure (Sereno 1997). A row of small osteoderms was present down the middle of the back. Ceratosaurus was a fairly typical theropod, with a large head, short forelimbs, robust hind legs, and a long tail. The skull of Ceratosaurus was quite large in proportion to the rest of its body. Each premaxilla contained only three teeth, and each maxilla (the main tooth-bearing bones in the upper jaw) held between twelve and fifteen flattened, exceptionally long teeth. Each dentary (the main tooth-bearing bone in the lower jaw) bore eleven to fifteen teeth. The prominent nose horn is formed from protuberances of the nasal bones. A juvenile specimen is known in which the two halves of the horn are not yet fused together. In addition to the large nasal horn, Ceratosaurus possessed smaller hornlike ridges in front of each eye, similar to those of Allosaurus. These ridges were formed by enlargement of the lacrimal bones. Uniquely among theropods, Ceratosaurus possessed dermal armor, in the form of small osteoderms running down the middle of its back. The tail of Ceratosaurus comprised about half of the body's total length. It was thin and flexible, with high vertebral spines. The type specimen was an individual about 17.5 feet (5.3 m) long; it is not clear whether this animal was fully grown. David B. Norman (1985) estimated that the maximum length of Ceratosaurus was 20 feet (6 m). A particularly large Ceratosaurus specimen from the Cleveland-Lloyd Quarry (UUVP 81), discovered in the mid-1960s, may have been up to 28.8 feet (8.8 m) long. Marsh (1884) suggested that Ceratosaurus weighed about half as much as Allosaurus. In Predatory Dinosaurs of the World, published in 1988, Gregory S. Paul estimated that the C. nasicornis holotype skeleton came from an animal weighing about 524 kilograms (1,160 lb). A large femur from the Cleveland-Lloyd Quarry represents a much bigger and heavier individual, whose bulk was estimated by Paul at about 980 kilograms (2,200 lb).
Utahraptor - Utahraptor ostrommaysorum
Utahraptor (meaning "Utah's predator" or "Utah thief") is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period (in rock strata dated to 126 ± 2.5 million years ago). It contains a single species, Utahraptor ostrommaysorum. The holotype specimen of Utahraptor is fragmentary, consisting of skull fragments, a tibia, claws and some caudal (tail) vertebra. These few elements suggest an animal about twice the size of Deinonychus. Like other dromaeosaurids, Utahraptor had large curved claws on their second toes. One claw specimen is preserved at 22 centimetres (8.7 in) in length and is thought to reach 24 centimetres (9.4 in) restored. The largest described U. ostrommaysorum specimens are estimated to have reached up to 7 m (23 ft) long and somewhat less than 500 kg (1,100 lb) in weight, comparable to a grizzly bear in size. Some undescribed specimens in the BYU collections may have reached up to 11 m (36 ft) long, though these await more detailed study. It is thought that Utahraptor may be closely related to the smaller Dromaeosaurus and the giant Mongolian dromaeosaurid genus Achillobator. Although feathers have never been found in association with Utahraptor specimens, there is strong phylogenetic evidence suggesting that all dromaeosaurids possessed them. This evidence comes from phylogenetic bracketing, which allows paleontologists to infer traits that exist in a clade based on the existence of that trait in a more basal form. The genus Microraptor is one of the oldest known dromaeosaurids, and is phylogenetically more primitive than Utahraptor. Since Microraptor possessed feathers, it is reasonable to assume that this trait was present in all of Dromaeosauridae. Feathers were very unlikely to have evolved more than once in dromaeosaurids, so assuming that Utahraptor lacked feathers would require positive evidence that they did not have them. So far, there is nothing to suggest that feathers were lost in larger, more derived species of dromaeosaurs. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 2 foot bones referred to Utahraptor were examined for signs of stress fracture, but none were found.
Ceratosaurus ( /ˌsɛrətɵˈsɔrəs/) meaning "horned lizard", in reference to the horn on its nose (Greek κερας/κερατος, keras/keratos meaning "horn" and σαυρος/sauros meaning "lizard"), was a large predatory theropod dinosaur from the Late Jurassic Period (Kimmeridgian to Tithonian), found in the Morrison Formation of North America, in Tanzania and Portugal. It was characterized by large jaws with blade-like teeth, a large, blade-like horn on the snout and a pair of hornlets over the eyes. The forelimbs were powerfully built but very short. The bones of the sacrum were fused (synsacrum) and the pelvic bones were fused together and to this structure (Sereno 1997). A row of small osteoderms was present down the middle of the back. Ceratosaurus was a fairly typical theropod, with a large head, short forelimbs, robust hind legs, and a long tail. The skull of Ceratosaurus was quite large in proportion to the rest of its body. Each premaxilla contained only three teeth, and each maxilla (the main tooth-bearing bones in the upper jaw) held between twelve and fifteen flattened, exceptionally long teeth. Each dentary (the main tooth-bearing bone in the lower jaw) bore eleven to fifteen teeth. The prominent nose horn is formed from protuberances of the nasal bones. A juvenile specimen is known in which the two halves of the horn are not yet fused together. In addition to the large nasal horn, Ceratosaurus possessed smaller hornlike ridges in front of each eye, similar to those of Allosaurus. These ridges were formed by enlargement of the lacrimal bones. Uniquely among theropods, Ceratosaurus possessed dermal armor, in the form of small osteoderms running down the middle of its back. The tail of Ceratosaurus comprised about half of the body's total length. It was thin and flexible, with high vertebral spines. The type specimen was an individual about 17.5 feet (5.3 m) long; it is not clear whether this animal was fully grown. David B. Norman (1985) estimated that the maximum length of Ceratosaurus was 20 feet (6 m). A particularly large Ceratosaurus specimen from the Cleveland-Lloyd Quarry (UUVP 81), discovered in the mid-1960s, may have been up to 28.8 feet (8.8 m) long. Marsh (1884) suggested that Ceratosaurus weighed about half as much as Allosaurus. In Predatory Dinosaurs of the World, published in 1988, Gregory S. Paul estimated that the C. nasicornis holotype skeleton came from an animal weighing about 524 kilograms (1,160 lb). A large femur from the Cleveland-Lloyd Quarry represents a much bigger and heavier individual, whose bulk was estimated by Paul at about 980 kilograms (2,200 lb).
Utahraptor - Utahraptor ostrommaysorum
Utahraptor (meaning "Utah's predator" or "Utah thief") is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period (in rock strata dated to 126 ± 2.5 million years ago). It contains a single species, Utahraptor ostrommaysorum. The holotype specimen of Utahraptor is fragmentary, consisting of skull fragments, a tibia, claws and some caudal (tail) vertebra. These few elements suggest an animal about twice the size of Deinonychus. Like other dromaeosaurids, Utahraptor had large curved claws on their second toes. One claw specimen is preserved at 22 centimetres (8.7 in) in length and is thought to reach 24 centimetres (9.4 in) restored. The largest described U. ostrommaysorum specimens are estimated to have reached up to 7 m (23 ft) long and somewhat less than 500 kg (1,100 lb) in weight, comparable to a grizzly bear in size. Some undescribed specimens in the BYU collections may have reached up to 11 m (36 ft) long, though these await more detailed study. It is thought that Utahraptor may be closely related to the smaller Dromaeosaurus and the giant Mongolian dromaeosaurid genus Achillobator. Although feathers have never been found in association with Utahraptor specimens, there is strong phylogenetic evidence suggesting that all dromaeosaurids possessed them. This evidence comes from phylogenetic bracketing, which allows paleontologists to infer traits that exist in a clade based on the existence of that trait in a more basal form. The genus Microraptor is one of the oldest known dromaeosaurids, and is phylogenetically more primitive than Utahraptor. Since Microraptor possessed feathers, it is reasonable to assume that this trait was present in all of Dromaeosauridae. Feathers were very unlikely to have evolved more than once in dromaeosaurids, so assuming that Utahraptor lacked feathers would require positive evidence that they did not have them. So far, there is nothing to suggest that feathers were lost in larger, more derived species of dromaeosaurs. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 2 foot bones referred to Utahraptor were examined for signs of stress fracture, but none were found.
