Post by Barry the Baryonyx on Jun 27, 2007 19:58:34 GMT -5
Ceratosaurus
Pic © Joe Tucciarone and Jeff Poling
Ceratosaurus / meaning 'horned lizard', in reference to the horn on its nose (Greek keras/keratos meaning 'horn' and sauros meaning 'lizard'), was a large predatory dinosaur from the Late Jurassic Period, found in the Morrison Formation of North America, in Tanzania and possibly in Portugal. It was characterized by large jaws with enormous, bladelike teeth, a large, blade-like horn on the snout and a pair 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) (i.e. similar to modern birds). Evidence suggests that there may also have been a row of small spurs or even a low sail, along the spine.
Discovery and species
Ceratosaurus is known from the Cleveland Lloyd Dinosaur Quarry in central Utah and the Dry Mesa Quarry in Colorado. The type species, described by O. C. Marsh in 1884 and redescribed by Gilmore in 1920, is Ceratosaurus nasicornis. Two further species have recently been described in 2000, C. magnicornis, and dentisulcatus. However, additional species, including C. ingens, C. stechowi and a species that has been referred to as C. meriani, from Portugal, have been described from less complete material. While C. nasicornis remains the type species and is cited at around 6 meters (20 feet) in length, additional finds indicate that this species may be misleadingly small, and that Ceratosaurus was likely larger. Very scant remains of a Ceratosaurus-like theropod have been found in Tanzania and would have belonged to an animal at least 15 meters (50 feet) in length, much larger than Allosaurus.
Paleobiology
Ceratosaurus lived alongside dinosaurs such as Allosaurus, Torvosaurus, Apatosaurus, Diplodocus, and Stegosaurus. It may have competed with Allosaurus for prey, though it was smaller at around 6 to 8 meters (20-27 feet) in length, weighing 500 kg up to 1 tonne. Ceratosaurus had a longer, more flexible body, with a tail shaped like a crocodilian. This suggests that it was a better swimmer than the stiffer Allosaurus. A recent study by Bakker confirmed that Ceratosaurs generally hunted aquatic prey, such as fish and crocodiles, although it had potential for feeding on large dinosaurs. The study also suggests that sometimes adults and juveniles ate together. This evidence is, of course, very debatable and Ceratosaurus tooth marks are very common on large, terrestrial dinosaur prey fossils.
Classification
Relatives of Ceratosaurus include Elaphrosaurus and the abelisaur Carnotaurus. The classification of Ceratosaurus and its immediate relatives has been under intense debate recently. In the past, Ceratosaurus, the Cretaceous Albelisaurs and the primitive Coelophysoidae were all grouped together and called Ceratosauria, defined as theropods closer to Ceratosaurus than to the lineage of aves. Recent evidence, however, has shown large distinctions between the later, larger and more advanced Ceratosaurs and earlier forms like Coelophysis, leading to the naming of the later theropods as Neoceratosauria and closer to, or perhaps even ancesteral to, Tetanuran carnosaurus like Allosaurus. Many Theropods no longer considered close to Ceratosaurus were once classified as relatives, including Eustreptospondylus and Yangchuanosaurus. While it is likely that they are not Neoceratosaurs these 'more advanced' theropods do display a sort of middle ground of primitive characteristics compared to Allosaurs (Eustreptospondylus lacks the Allosaur expanded boot-shaped pubic bone, instead having a rod shaped pubis like Ceratosaurus. Many Sinraptors and Allosaurs have a tendency to grow elaborate and multiple horn rows, very visible in Yangchuanosaurus and prominent in Ceratosaurus). Some of the most modern publishings have even begun listing Ceratosaurus as a basal Tetanurae and closer to Allosaurus than Coelophysis. While considered distant from the lineage of aves among the theropods, Ceratosaurus and its kin were still very bird-like and even had a more 'advanced-looking tarsus than Allosaurus. As with all dinosaurs, the more fossils found of these animals, the better their evolution and relationships can be understood.
Info Copyright © 2006 Answers Corporation
Pic © Joe Tucciarone and Jeff Poling
Ceratosaurus / meaning 'horned lizard', in reference to the horn on its nose (Greek keras/keratos meaning 'horn' and sauros meaning 'lizard'), was a large predatory dinosaur from the Late Jurassic Period, found in the Morrison Formation of North America, in Tanzania and possibly in Portugal. It was characterized by large jaws with enormous, bladelike teeth, a large, blade-like horn on the snout and a pair 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) (i.e. similar to modern birds). Evidence suggests that there may also have been a row of small spurs or even a low sail, along the spine.
Discovery and species
Ceratosaurus is known from the Cleveland Lloyd Dinosaur Quarry in central Utah and the Dry Mesa Quarry in Colorado. The type species, described by O. C. Marsh in 1884 and redescribed by Gilmore in 1920, is Ceratosaurus nasicornis. Two further species have recently been described in 2000, C. magnicornis, and dentisulcatus. However, additional species, including C. ingens, C. stechowi and a species that has been referred to as C. meriani, from Portugal, have been described from less complete material. While C. nasicornis remains the type species and is cited at around 6 meters (20 feet) in length, additional finds indicate that this species may be misleadingly small, and that Ceratosaurus was likely larger. Very scant remains of a Ceratosaurus-like theropod have been found in Tanzania and would have belonged to an animal at least 15 meters (50 feet) in length, much larger than Allosaurus.
Paleobiology
Ceratosaurus lived alongside dinosaurs such as Allosaurus, Torvosaurus, Apatosaurus, Diplodocus, and Stegosaurus. It may have competed with Allosaurus for prey, though it was smaller at around 6 to 8 meters (20-27 feet) in length, weighing 500 kg up to 1 tonne. Ceratosaurus had a longer, more flexible body, with a tail shaped like a crocodilian. This suggests that it was a better swimmer than the stiffer Allosaurus. A recent study by Bakker confirmed that Ceratosaurs generally hunted aquatic prey, such as fish and crocodiles, although it had potential for feeding on large dinosaurs. The study also suggests that sometimes adults and juveniles ate together. This evidence is, of course, very debatable and Ceratosaurus tooth marks are very common on large, terrestrial dinosaur prey fossils.
Classification
Relatives of Ceratosaurus include Elaphrosaurus and the abelisaur Carnotaurus. The classification of Ceratosaurus and its immediate relatives has been under intense debate recently. In the past, Ceratosaurus, the Cretaceous Albelisaurs and the primitive Coelophysoidae were all grouped together and called Ceratosauria, defined as theropods closer to Ceratosaurus than to the lineage of aves. Recent evidence, however, has shown large distinctions between the later, larger and more advanced Ceratosaurs and earlier forms like Coelophysis, leading to the naming of the later theropods as Neoceratosauria and closer to, or perhaps even ancesteral to, Tetanuran carnosaurus like Allosaurus. Many Theropods no longer considered close to Ceratosaurus were once classified as relatives, including Eustreptospondylus and Yangchuanosaurus. While it is likely that they are not Neoceratosaurs these 'more advanced' theropods do display a sort of middle ground of primitive characteristics compared to Allosaurs (Eustreptospondylus lacks the Allosaur expanded boot-shaped pubic bone, instead having a rod shaped pubis like Ceratosaurus. Many Sinraptors and Allosaurs have a tendency to grow elaborate and multiple horn rows, very visible in Yangchuanosaurus and prominent in Ceratosaurus). Some of the most modern publishings have even begun listing Ceratosaurus as a basal Tetanurae and closer to Allosaurus than Coelophysis. While considered distant from the lineage of aves among the theropods, Ceratosaurus and its kin were still very bird-like and even had a more 'advanced-looking tarsus than Allosaurus. As with all dinosaurs, the more fossils found of these animals, the better their evolution and relationships can be understood.
Info Copyright © 2006 Answers Corporation
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