Post by DinosaurMichael on Mar 11, 2012 8:27:37 GMT -5
BoarCroc - Kaprosuchus saharicus
Kaprosuchus is an extinct genus of mahajangasuchid crocodyliform. It is known from a single nearly complete skull collected from the Upper Cretaceous Echkar Formation of Niger. The name means "boar crocodile" from the Greek kapros ("boar") and souchos ("crocodile") in reference to its unusually large caniniform teeth which resemble those of a boar. It has been nicknamed "BoarCroc" by Paul Sereno and Hans Larsson, who first described the genus in a monograph published in ZooKeys in 2009 along with other Saharan crocodyliformes such as Anatosuchus and Laganosuchus. The type species is K. saharicus. Kaprosuchus is estimated to have been around 6 metres (20 feet) in length. It possesses three sets of tusk-like caniniform teeth that project above and below the skull, one of which in the lower jaw fits into notches in upper jaw. This type of dentition is not seen in any other known crocodyliform. Another unique characteristic of Kaprosuchus is the presence of large, rugose horns formed from the squamosal and parietal bones that project posteriorly from the skull. Smaller projections are also seen in the closely related Mahajangasuchus. The snout of Kaprosuchus shows generalized proportions and the naris is positioned dorsally. In Kaprosuchus many teeth are hypertrophied and labiolingually (laterally) compressed, unlike those of crocodyliforms with similarly shallow snouts, which are usually subconical and of moderate length. Another difference between the skull of Kaprosuchus and those of crocodyliforms that also possess dorsoventrally compressed snouts is the great depth of the posterior portion of the skull. In Kaprosuchus, the orbits (i.e., eye sockets) open laterally and are angled slightly forward rather than upward. The orbits turned forward suggest that there was somewhat stereoscopic vision, i.e., an overlap in the visual field of the animal. The surfaces of the premaxillae are rugose with the edges elevated above the body of the bone, suggesting that a keratinous shield would have been supported by the rugosities at the tip of the snout. Along the interpremaxillary suture, the area where the two premaxillae meet, the surface is smooth, giving the paired rugosity of the premaxillae the resemblance of a moustache in anterior view.
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.
Kaprosuchus is an extinct genus of mahajangasuchid crocodyliform. It is known from a single nearly complete skull collected from the Upper Cretaceous Echkar Formation of Niger. The name means "boar crocodile" from the Greek kapros ("boar") and souchos ("crocodile") in reference to its unusually large caniniform teeth which resemble those of a boar. It has been nicknamed "BoarCroc" by Paul Sereno and Hans Larsson, who first described the genus in a monograph published in ZooKeys in 2009 along with other Saharan crocodyliformes such as Anatosuchus and Laganosuchus. The type species is K. saharicus. Kaprosuchus is estimated to have been around 6 metres (20 feet) in length. It possesses three sets of tusk-like caniniform teeth that project above and below the skull, one of which in the lower jaw fits into notches in upper jaw. This type of dentition is not seen in any other known crocodyliform. Another unique characteristic of Kaprosuchus is the presence of large, rugose horns formed from the squamosal and parietal bones that project posteriorly from the skull. Smaller projections are also seen in the closely related Mahajangasuchus. The snout of Kaprosuchus shows generalized proportions and the naris is positioned dorsally. In Kaprosuchus many teeth are hypertrophied and labiolingually (laterally) compressed, unlike those of crocodyliforms with similarly shallow snouts, which are usually subconical and of moderate length. Another difference between the skull of Kaprosuchus and those of crocodyliforms that also possess dorsoventrally compressed snouts is the great depth of the posterior portion of the skull. In Kaprosuchus, the orbits (i.e., eye sockets) open laterally and are angled slightly forward rather than upward. The orbits turned forward suggest that there was somewhat stereoscopic vision, i.e., an overlap in the visual field of the animal. The surfaces of the premaxillae are rugose with the edges elevated above the body of the bone, suggesting that a keratinous shield would have been supported by the rugosities at the tip of the snout. Along the interpremaxillary suture, the area where the two premaxillae meet, the surface is smooth, giving the paired rugosity of the premaxillae the resemblance of a moustache in anterior view.
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.
