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ANATOMY
Albertosaurus was a relative of Tyrannosaurus rex; Albertosaurus was smaller than T. rex and lived a few million years earlier. Albertosaurus walked on two legs and had a large head with sharp, saw-toothed teeth. It had two-fingered hands on short arms. Its long tail provided balance and quick turning. It had powerful back legs with clawed, three-toed feet.

Albertosaurus was about 30 feet (9 m) long, about 11 feet (3.4 m) tall at the hips, and up to 3 tons in weight (averaging roughly 2500 kg). The lower jaw of Albertosaurus had from 14 and 16 teeth; the upper jaw had 17-19 teeth. It had one row of teeth in each jaw but had at least one replacement tooth growing up from under each tooth.

Albertosaurus was a theropod from the late Cretaceous period at the end of the Mesozoic Era.
The Theropods were fast, two-legged carnivores (animal eaters) with short arms. The following are Theropod characteristics: Speed and agility Carnivorous diet Sharp, slicing teeth and well-developed jaw muscles Bipedal walk Strong legs with bird-like, three-toed, clawed feet Hollow bones (like birds).

WHEN ALBERTOSAURUS LIVED
Albertosaurus lived in the late Cretaceous period, about 76-74 million years ago, toward the end of the Mesozoic, the Age of Reptiles.

DIET
Albertosaurus was a carnivore (a meat eater). It probably ate plant-eating dinosaurs.

A PACK OF ALBERTOSAURUS
paleontologist Philip Currie found nine Albertosaurus sarcophagus fossils together. Since these dinosaurs were of different ages, they were probably from a herd/pack that lived together (at least temporarily). The idea of a pack of these enormous predators hunting together is extrmely scary.

LOCOMOTION
Albertosaurus walked on two muscular legs. There has been some debate, though, on whether or not the massive, short-armed theropods (like T. rex, Giganotosaurus, Albertosaurus, and Allosaurus) could run very fast because if they fell, their short arms would not break their fall and they would be badly injured (James Farlow, 1995). This meant that these large theropods were slow, lumbering animals.

Dr. Bruce Rothschild, of the Arthritis Center of Northeast Ohio, has found evidence of 14 fractured ribs in an Allosaurus that reflect healed injuries that were probably received in falls. These were most likely bellyflops that happened while running (as reported in the April 16, 1998 New Scientist).

An x-ray analysis of the Allosaurus fossil indicated that the Allosaurus ribs near the scapula (the shoulder bone) were cracked and had healed. The Allosaurus was capable of recovering after many severe forwards tumbles that probably occurred while it was running. So the suggestion that perhaps the large short-armed theropods were not capable of running because they couldn't recover after a fall apparently wasn't so, at least for Allosaurus - this Allosaurus did recover many times after bad tumbles.

In 1995 James Farlow of Indiana-Purdue University argued that a large T. rex could run no faster than 20 mph (32 kph), because if it did, a fall would probably be so severe as to kill it. T. rex weighed about 6 tons and was up to 20 feet (6 m) tall but Allosaurus was slightly smaller, about 3 tons and 16.5 feet (5 m) long. Farlow says that Rothschild's analysis is consistent with his theory since Allosaurus was smaller than T. rex (its smaller mass would make the impact much less powerful so the animal may have been able to recover after a running fall). Albertosaurus was also smaller than T. rex and may have been a fast runner.

DISCOVERY OF FOSSILS
Albertosaurus was first unearthed by Joseph Burr Tyrrell in western Canada in 1884. Albertosaurus was named in 1884 by H. F. Osborn. Many Albertosaurus fossils have been found in Alberta, Canada and in the western USA. Fossils called Gorgosaurus turned out to be juvenile (young) examples of Albertosaurus.

CLASSIFICATION
Albertosaurus belonged to the:

• Kingdom Animalia (animals)
• Phylum Chordata (having a hollow nerve chord ending in a brain)
• Class Archosauria (diapsids with socket-set teeth, etc.)
• Order Saurischia - lizard-hipped dinosaurs
• Suborder Theropoda - bipedal carnivores
• Infraorder Coelurosauria - lightly-built fast-running predators with hollow bones and large brains
• Superfamily Maniraptoriformes - advanced coelurosaurs with a fused wrist bone
• Family Tyrannosauroidea - huge predators with small arms and two-fingered hands
• Genus Albertosaurus
  • species sarcophagus (the type species; Osborn, 1905)
  • species grandis (Marsh, 1890, a dubious species, originally Ornithomimus)

Note: Gorgosaurus used to be thought to be an invalid name for Albertosaurus, but is now believed to be a separate genus of tyrannosaurids
ALBERTOSAURUS LINKS
Albertosaurus Printout
Albertosaurus at the Royal Tyrrell Museum, Canada
Known Albertosaurus specimens

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