Allosaurus

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Allosaurus

Height: 16 ft (4.5 m)

Length: 40 ft (12 m)

Weight: 2,000-8,800 lbs (907-3991 kg)

Diet: Carnivore

Found: North America (Montana, Wyoming, Colorado, New Mexico, Oklahoma, Utah, South Dakota), Portugal.

Time Period: Jurassic

Size and Looks

The Allosaurus was about 16 feet tall and 40 feet long. This made it a large and powerful predator. It had more than 70 individual teeth that were serrated and were probably used to slice flesh rather than crush bone like the Tyrannosaurus Rex. It had two horns on its head that were probably used for signaling to other dinosaurs of the same species. Allosaurus also had three fingers with giant claws that were probably used to claw and hold herbivorous dinosaurs while killing them.

Diet

The Allosaurus was a large carnivore. It had an interesting jaw that would let it open very wide. We think that it used an attack model like some birds of prey. The strike and tear model. The Allosaurus would bite on its prey and hold it then it would bite. We know it sometimes hunted the Stegosaurus because we found a Stegosaurus plate with Allosaurus bite marks imprinted on it. The Stegosaurus is heavily armored with giant bone plates going down its long back and a long tail with four giant spikes at the end that would have been used to wack a predator if it got too close. So if the Allosaurus was hunting this giant it would need to be stealthy and fast. And it was both of those, the Allosaurus could run up to 34 miles per hour. It also would have hunted other animals that lived in the Jurassic.

Discovery

Ferdinand Hayden, an American geologist, found what is thought to be the first Allosaurus bone somewhere in Colorado. Joseph Leidy got the bone and named the dinosaur Antrodemus. Antrodemus is the name that many paleontologists used instead of Allosaurus for a long time. During the bone wars, another Allosaurus skeleton was found in 1877 and named by Othniel Charles Marsh. This skeleton only had a tooth, a dorsal vertebra, and a toe bone. Marsh named this animal Allosaurus fragilis. But Marshes rival Edward Drinker Cope named got a new dinosaur skeleton that was also very fragmentary. It compiled of three vertebrae, a coracoid, and a metatarsal. Cope named it Epanterias amplexus. Epanterias amplexus was also an Allosaurus but at that time they did not know that. Both of these were found in Garden Parks Colorado. After Marsh and Cope died another paleontologist named H. F. Hubbell looked at these skeletons and decide that they were the same species.

Cleveland-Lloyd Quarry

In the Cleveland-Lloyd Quarry, hundreds of Allosaurus bones were found. In fact, over 10,000 bones have been found there and those 10,000 bones represent 47 individuals. A paleontologist named James Madison worked there and was in charge of all these bones. He was the person who started to call the dinosaur Allosaurus instead of Antrodemus. Later in honor of him, A. jimmadseni was named after him.


For more information on the history of Allosaurus check out this video by Benjamin Burger: https://www.youtube.com/watch?v=raINX8sB-68


Allosaurus Species

There are currently three species of Allosaurus. A. fragilis, A. jimmadseni, and A. europaeus.

A. fragilis

A. fragilis is the species of Allosaurus that most people think of when they think of Allosaurus. Its snout is a little taller than the other species. It has a larger crest over its eye but not much crest on the nasal bones. It has a jugal bone that curves up.

A. jimmadseni

A. jimmadseni was named after James Madison, a paleontologist that spent a lot of time working on allosaurus bones in the Cleveland-Lloyd quarry. It has a thinner snout, with a jugal bone that does not curve at all. Its crest over its eye is more pronounced and so is the nasal crest.

A. europaeus

A. europaeus was found in Portugal, hence the name A. europaeus. It has a snout that is more in between the width of A. fragilis and the thinness of A. jimmadseni, but the jugal bone curve is very similar to A. fragilis. The crest over its eye is smaller than the other species but the crest over its nose is more pronounced.

Image by Chure and Loewen published in PeerJ



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Baron, Matthew G., and Dieter Braun. Dictionary of Dinosaurs. Wide Eyed Editions, 2018.

Pim, Keiron. Dinosaurs the Grand Tour: Everything Worth Knowing about Dinosaurs from Aardonyx to Zuniceratops. The Experiment, 2019.

Allosaurus, scienceviews.com/dinosaurs/allosaurus.html#:~:text=The%20Allosaurus%20was%20first%20discovered,named%20by%20Othniel%20Charles%20Marsh.&text=Later%2C%20in%20the%20Cleveland%2DLloyd,later%20named%20the%20state%20fossil.

“Lecture 50c The Story of Allosaurus.” YouTube, YouTube, 10 Feb. 2020, www.youtube.com/watch?v=raINX8sB-68.

“A New Species of Allosaurus - Allosaurus Jimmadseni.” Everything Dinosaur Blog, 29 Jan. 2020, blog.everythingdinosaur.co.uk/blog/_archives/2020/01/27/a-new-species-of-allosaurus-allosaurus-jimmadseni.html#:~:text=The%20newly%20described%20Allosaurus%20jimmadseni,feeding%20behaviour%20between%20the%20two.%E2%80%9D.

Kowinsky, J. “Allosaurus - Facts about the Apex Predator of the Morrison.” Allosaurus - Facts About The Famous Jurassic Dinsaur, 15 Feb. 2021, www.fossilguy.com/gallery/vert/dinosaur/allosaurus/index.htm.