Post by DinosaurMichael on Jan 17, 2012 17:54:41 GMT -5
Megalania - Varanus priscus
Megalania ("great roamer"; Greek Μέγας "great" + ἀλαίνω "roam") is a giant extinct goanna or monitor lizard. It was part of a megafaunal assemblage that inhabited southern Australia during the Pleistocene, and appears to have disappeared around 40,000 years ago. The first aboriginal settlers of Australia may have encountered living Megalania. The name Megalania prisca was coined by Sir Richard Owen to mean "Ancient Great Roamer"; the name was intended to "reference to the terrestrial nature of the great Saurian". Owen used a modification of the Greek word ἠλαίνω ēlainō ("I roam"). The close similarity to the Latin word: lania (feminine form of "butcher") has resulted in numerous taxonomic and popular descriptions of Megalania mistranslating the name as: Ancient Giant Butcher. Megalania prisca was originally classified in its own monotypic genus. Its status as a valid genus remains controversial, with many authors preferring to consider it a junior synonym of Varanus, which encompasses all living monitor lizards. As the gender of the genera Megalania and Varanus are different (feminine and masculine, respectively), the epithet prisca changes to priscus (in alignment with the Code of the ICZN). Several studies have attempted to establish the phylogenetic position of Megalania within the Varanidae. An affinity with the Perentie, Australia's largest living lizard, has been suggested based on skull-roof morphology. The most recent comprehensive study proposes a sister-taxon relationship with the Komodo dragon based on neurocranial similarities, with the Lace monitor as the closest living Australian relative. Conversely, the Perentie is considered more closely related to the Gould's and Argus monitors. The lack of complete, or nearly complete fossil skeletons has made it difficult to determine the exact dimensions of Megalania. Early estimates placed the length of the largest individuals at 7 metres (23 ft), with a maximum weight of approximately 600–620 kilograms (1,300–1,400 lb). However, more recent and more rigorous studies give very different results from one another. In 2002, Stephen Wroe determined that Megalania had a maximum length of 4.5 metres (15 ft) and a weight of 331 kilograms (730 lb), while its average length would have been around 3.5 metres (11 ft), and mean body weight would have been between 97–158 kilograms (210–350 lb). He concluded that the earlier estimates reaching lengths of 6 metres (20 ft) or more and a weight of several tons were exaggerations based upon flawed methodologies. However, Ralph Molnar in 2004 determined a range of potential sizes for Megalania (made by scaling up from dorsal vertebrae, after he determined a relationship between dorsal vertebrae length and total body length). If it had a long thin tail like the Lace monitor (Varanus varius), then it would have reached a length of 7.9 metres (26 ft), while if its tail-to-body proportions were more similar to that of the Komodo dragon, then a length of around 7 metres (23 ft) is more likely. Taking the maximal 7 m length, he estimated a weight of 1,940 kilograms (4,300 lb), with a leaner 320 kilograms (710 lb) being average.
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.
Megalania ("great roamer"; Greek Μέγας "great" + ἀλαίνω "roam") is a giant extinct goanna or monitor lizard. It was part of a megafaunal assemblage that inhabited southern Australia during the Pleistocene, and appears to have disappeared around 40,000 years ago. The first aboriginal settlers of Australia may have encountered living Megalania. The name Megalania prisca was coined by Sir Richard Owen to mean "Ancient Great Roamer"; the name was intended to "reference to the terrestrial nature of the great Saurian". Owen used a modification of the Greek word ἠλαίνω ēlainō ("I roam"). The close similarity to the Latin word: lania (feminine form of "butcher") has resulted in numerous taxonomic and popular descriptions of Megalania mistranslating the name as: Ancient Giant Butcher. Megalania prisca was originally classified in its own monotypic genus. Its status as a valid genus remains controversial, with many authors preferring to consider it a junior synonym of Varanus, which encompasses all living monitor lizards. As the gender of the genera Megalania and Varanus are different (feminine and masculine, respectively), the epithet prisca changes to priscus (in alignment with the Code of the ICZN). Several studies have attempted to establish the phylogenetic position of Megalania within the Varanidae. An affinity with the Perentie, Australia's largest living lizard, has been suggested based on skull-roof morphology. The most recent comprehensive study proposes a sister-taxon relationship with the Komodo dragon based on neurocranial similarities, with the Lace monitor as the closest living Australian relative. Conversely, the Perentie is considered more closely related to the Gould's and Argus monitors. The lack of complete, or nearly complete fossil skeletons has made it difficult to determine the exact dimensions of Megalania. Early estimates placed the length of the largest individuals at 7 metres (23 ft), with a maximum weight of approximately 600–620 kilograms (1,300–1,400 lb). However, more recent and more rigorous studies give very different results from one another. In 2002, Stephen Wroe determined that Megalania had a maximum length of 4.5 metres (15 ft) and a weight of 331 kilograms (730 lb), while its average length would have been around 3.5 metres (11 ft), and mean body weight would have been between 97–158 kilograms (210–350 lb). He concluded that the earlier estimates reaching lengths of 6 metres (20 ft) or more and a weight of several tons were exaggerations based upon flawed methodologies. However, Ralph Molnar in 2004 determined a range of potential sizes for Megalania (made by scaling up from dorsal vertebrae, after he determined a relationship between dorsal vertebrae length and total body length). If it had a long thin tail like the Lace monitor (Varanus varius), then it would have reached a length of 7.9 metres (26 ft), while if its tail-to-body proportions were more similar to that of the Komodo dragon, then a length of around 7 metres (23 ft) is more likely. Taking the maximal 7 m length, he estimated a weight of 1,940 kilograms (4,300 lb), with a leaner 320 kilograms (710 lb) being average.
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.
