Allosaurus jimmadseni

A large carnivorous dinosaur the size of a bus that slashed its prey to death has been recognized as a new species 30 years after its remains were dug up in Utah. Allosaurus jimmadseni

The remains of the meat-eating Allosaurus jimmadseni uncovered by scientists in 1990. Which roamed the North American flood plains 155 million years ago.

A study of the bones of A. jimmadseni has been published in the famous journal PeerJ. It took seven years of hardworking to prepare the bones of this giant for analysis.

The 4,000-pound beast reached lengths of up to 29 feet and, much like the Tyrannosaurs rex, it ran on two legs.

However, according to recent studies, remains of these revealed that A.jimmadseni’s longer arms would have made it an even better hunter than the notoriously blood-thirsty T. rex.

Recognising a new species of dinosaur in rocks that have been intensely investigated for over 150 years is an outstanding experience of discovery,’ said Dr Daniel Chure, a retired palaeontologist at the Dinosaur National Monument in north-eastern Utah and co-lead author on the study.

A.jimmadseni and T. rex have a different skeletal structure, that is why it has been described as, an entirely new species.

According to Professor Mark Loewen(co lead author), of the Natural History Museum of Utah ‘The skull of Allosaurus jimmadseni is more lightly built than its later relative Allosaurus fragilis, suggesting a different feeding behaviour between the two,’.

However, the new dinosaur’s head was flatter and weaker than A. fragilis, and it had worse eyesight, with a narrower field of vision which suggests that it had more difficulty in catching its prey.

The bones structure of Allosaurus jimmadseni indicates that it possessed a unique upper jaw and cheeks, while a decorative crest stretched from its horns to the eyes, just in front of the nose.

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Dr. Brent Breithaupt, the regional paleontologist for the Bureau of Land Management, Cheyenne, Wyoming said ‘this exciting new study illustrates the importance of continued paleontological investigations on public lands in the West. Discovery of this new taxon of dinosaur will provide important information about the life and times of Jurassic dinosaurs and represents another unique component of America’s Heritage.’

Allosaurus jimmadseniA.jimmadseni inhabited the flood plains of western North America during the Late Jurassic period, evolving around 155 million years ago, at least five million years before Allosaurus fragilis.

Paleontologists say A. jimmadseni would have lived on the semi-arid Morrison Formation floodplains throughout the western interior of North America – including land that’s now part of Utah, Colorado and Wyoming.

Early Morrison Formation dinosaurs were replaced by some of the most famous dinosaurs of the Late Jurassic period, including Diplodocus and Stegosaurus.

The new species’ almost complete skeleton has been unveiled at the Natural History Museum of Utah

It was back in 1990 that George Engelmann of the University of Nebraska, Omaha initially discovered the initial skeleton of the new species within Dinosaur National Monument, a national park bordering Colorado and Utah that preserves an abundance of dinosaur fossils.

Six years after the headless skeleton was collected, the radioactive skull belonging to the skeleton was uncovered using a radiation detector by Ramal Jones of the University of Utah.

A. jimmadseni has been named after Utah’s state paleontologist James H Madsen Jr, who died in 2009 after excavating and studying tens of thousands of Allosaurus bones.

The origin tree of dinosaurs

dinosoraus origin treeThe diagram represents the family tree of Dinosaurs.

What is Allosaurus?

Allosaurus is a genus of carnivorous theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period. They were typically a large theropod, having a massive skull on a short neck, a long, slightly sloping tail, and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of 8.5 m (28 ft), with the largest definitive Allosaurus specimen (AMNH 680) estimated at 9.7 meters (32 feet) long, and an estimated weight of 2.3 metric tons (2.5 short tons).

Currently, there is six species of Allosaurus are known including the recently discovered Allosaurus jimmadseni.

  1. A. amplus
  2. A. atrox
  3. A. europaeus
  4. A. fragilis
  5. A. jimmadseni
  6. A. lucasi


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