Albertosaurus

General information

LAlbertosaurus Osborn 1905 is a carnivore which measured 8 to 9 meters length and lived with the Crétacé superior (Campanien (83,5 to 70,6) with the Maastrichtien (70,6 to 65,5 million years)) there are 70 to 75 million years, in current the Canada. At the place where it was found (Alberta), one created a National park of dinosaurs, the Royal Tyrrell Museum off Paleontology. More than 350 skeletons of dinosaurs were discovered at this place.

Its name means Lézard of Alberta

Time: Cretaceous (- 144 M.A. with - 65 M.A.)

Size: 11 m of length, 4,5 m in height, 2,7 tons

Habitat: Food America

Mode: carnivore

Etymology

Albertosaurus was named by Henry Fairfield Osborn in a very short note, at the end of its description in 1905 of the Tyrannosaure ( Tyrannosaurus rex ). The name honors Alberta, the Canadian province in which the first remainders have summer found. The generic name incorporates also the Greek term sauros (“lizard”), the suffix it more common in the names of dinosaur. The species of the type is A. sarcophagus , which means “eater of flesh” and with the same etymology as the funerary container of which it shares the name: a combination of words Greek old sarx (“flesh”) and phagein (“to eat”).

Anatomy

The Albertosaurus , like other carnosaures was a frightening predator of the period of the Cretaceous. It had powerful hands and feet griffus, rear limbs, teeth sharpened like razors and a resistant cranium to protect itself when it sank on its preys. The enormous cranium of Albertosaurus was made to resist the shocks when it threw mouth open on its preys. Its jaws impressive were equipped with sharp-edged teeth. Very compact vertebrae gave to the neck of albertosaurus its curve and its mobility. When this dinosaur bit a prey, powerful muscles of the neck raised the massive head and drew it behind, tearing off scraps of flesh.

Inventory of the found fossils

The standard specimen is a partial cranium, collected in 1884, in an outcrop of the Horseshoe Formation Canyon close to the River Red Deer To rivet in Alberta, by the famous geologist Joseph Burr Tyrrell. In 1910, the American paleontologist Barnum Brown discovered the remainders of a great group of Albertosaurus close to the River Red Deer To rivet. Because of the great number of bone and limited time, Barnum Brown does not have collected each specimen, but ensured itself to collect remainders of each individuals who would be identified in the bonebed. The Royal Tyrrell Museum off Paleontology has redécouvert the bonebed in 1997 and research has begun again on the site which is inside Dry Island Buffalo Jump Provincial Park. A fuller excavation, of 1997 to 2005, raised the remainders of more than 13 individuals of various ages, including subject a two years old (50 kg, 2 m length) and a very old individual (28 years) estimated at more than 10 meters of length. None of these individuals is known by a complete skeleton, and they are represented by remainders in various museums. The majority of Albertosaurus were 14 years old and more at the time of their death. The youthful ones are seldom found because of a less good safeguarding of the small bones of the youngest animals and owing to the fact that them collectors notice less the smallest fossils. It is possible also that Albertosaurus lately hatched died in great numbers, but were not fossilized because of their small size and their fragile construction. The Albertosaurus young people were relatively tall for animals of youthful, but their remainders are always rare compared to those of the adults. The most death rate of the adults can explain their more common safeguarding. The very large ones animals were rare because few individuals have survived long enough to reach such sizes. The high death rates of small, followed by mortality reduced among the youthful ones and a sudden increase in mortality after sexual maturity, with very few animals reaching the maximum size, is a model observed at many large modern mammals, including the elephant S, the African Buffalo, and the Rhinoceros. The same model is observed also at others tyrannosauridés.

Behavior

The bonebed of Dry Island discovered by Barnum Brown and its team contains the remainders of 22 Albertosaurus. The group seems to be made up of a very old adult; of eight old adults from 17 to 23 years; of seven under-adults undergoing their phase of growth rapids between 12 to 16 years; and of six youthful between 2 and 11 years, which did not have not reached the phase of growth yet. Almost the absence of remainders of herbivores and the similar state of safeguarding of much of individuals brought Phil Currie to conclude that the area was not a trap of predatory like Brea Tar Pits in California, and that all the preserved animals died at the same time. Currie claims this like the proof of a behavior of group. Other scientists are skeptics, observing that the animals could be led together by the dryness, a flood or for other reasons. There is abundance of evidence of a sociable behavior among the herbivorous dinosaurs, including at the ceratopsiens and the hadrosaures. However, it is rare that as many predatory dinosauriens are discovered on the same site. Small theropodes like Deinonychus, Coelophysis and Megapnosaurus (Syntarsus) rhodesiensis was discovered in aggregation, as well as larger predatory like Allosaurus and Mapusaurus. There is some evidence of sociable behavior at others tyrannosauridés. The fragmentary remainders of smaller individuals were found beside “Known” tyrannosaure of Field Museum off Natural History of Chicago, and a bonebed of Two Medicine Formation of Montana contains with less three specimens of Daspletosaurus, preserved beside several hadrosaures. These conclusions can confirm the proof of a social behavior at Albertosaurus, although it is possible that it acts that temporary or abnormal aggregations. Some speculated that as in certain groups social, they could have behaved like the dragons of Komodo attacking of the corpses, where the aggressive competition leading some of predatory to be killed and cannibalized. Currie considers as the possibility as Albertosaurus drove out in group and that youngest members folded back their prey towards the adults, who were larger and more powerful, but also slower. The youthful ones could have as had manners of living different as the adults, filling the niches the predatory ones between the enormous adults and the theropodes contemporary more small. A similar situation is observed at the dragons of Komodo, with the lately hatched animals which begin the life like the small insectivorous ones before growing to become the predatory dominant ones on their islands. However, as the safeguarding of the behavior is extremely rare, these ideas cannot to be easily checked.

References

Erickson, Gregory Mr.; Currie, Philip. J.; Inouye, Brian D.; & Wynn, Alice A. (2006). " Tyrannosaur life tables: year example off nonavian dinosaur population biology". Science 313:213 - 217. DOI: 10.1126/science.1125721

Currie, Philip J. (1998). " Possible obviousness off gregarious behavior in tyrannosaurids". Gaia 15:271 - 277.

Roach, Brian T.; & Brinkman, Daniel T. (2007). " With revaluation off co-operative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs". Bulletin off the Peabody Museum off Natural History 48 (1): 103-138.

Internal bonds

See List of the dinosaurs

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