An Allosaurus was a large dino from North America and is a Utah state fossil. Though it looked similar to a T-rex, Allosaurus, and T-rex were not closely related. The Allosaurus had sharp teeth and binocular vision, which helped them hunt Stegosauruses and other prey animals.
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Some Quick Facts About the Allosaurus
| Name | Allosaurus fragilis (Greek for Different lizard) |
| Type of dinosaur | Large Theropod dinosaur from the Allosauridae family |
| Territory | Plains of North America, including Colorado, New Mexico, and Utah |
| Size | Big, 28-32 feet long,13-16 feet tall |
| Color | Blue/green-ish gray top and cream underside |
| Interesting Characteristics | Useful forelimbs, carnivore but also fed on carcasses |
| Diet | Scavenging and hunting carnivorous dinosaur |
| Major Threats | Habitat loss, climate change |
The Allosaurus was one of North America’s biggest and most vicious Jurassic dinosaurs. Allo had huge hindlimbs and longer forelimbs than the Tyrannosaurs. This sharp-toothed reptile was a carnivore that ate the Stegosaurus!
When and Where Did the Allosaurus Live?
The Allosaurus lived about 155-145 million years ago in the Late Jurassic period. Over 60 Allosaurus fossils surfaced in the Morrison Formation in the 1800s. The Morrison Formation extends through several states, including:
- Colorado
- Montana
- New Mexico
- Oklahoma
- South Dakota
- Utah
- Wyoming
Allosaurs fossils have also came up in Germany, Portugal, and Tanzania. Those places might seem really far away from North America, but that’s because there was only one continent until it started separating in the Triassic period. From the Triassic through the Cretaceous, there were two continents–Laurasia and Gondwana, but they were still really close together.
What other dinos did the Allosaurus live with?
The Allosaurus lived with other Theropoda dinos. Ceratosaurus fossils have been found in the same areas as Allo, though Cerato stayed close to the water and out of Allo’s way. A Torvosaurus also lived in the same period as the Allosaurus but preferred marsh areas like the Ceratosaurus.
Were Allosaurus dinos bigger than T. rex?
The Tyrannosaurus rex was bigger and heavier than the Allosaurus. Luckily for the Allosaurus, the T-rex wasn’t around until the late Cretaceous period, millions of years after Allo went extinct. If the two had lived simultaneously, the T-rex would easily outcompeted Allo for food and territory.
What did the Allosaurus eat?
The Allosaurus was a carnivore. It ate other animals like dinos, prehistoric mammals, and other reptiles. Allo was both a hunter and a scavenger, eating carcasses when they had the opportunity.
a Stegosaurus was a common meal for the Allosaurus. Bite marks on Stegosaurus fossils match Allo’s teeth. Allo also ate Sauropods like Apatosaurus and Brachiosaurus and the occasional Dryosaurus.
How Many Species of Allosaurus Are There?
So far, there are six known Allosaurus species. Allosaurus fragilis is the type species. The name A. fragilis was given to the Allosaurus by paleontologist Marsh in 1877.
The six species are:
- A. amplus
- A. atrox
- A. europaeus
- A. fragilis
- A. jimmadseni
- A. lucasi
A. jimmadseni is a new species name given in 2020. A. jimmadseni fossils were originally found in 1990 in the Dinosaur National Monument area of the Morrison Formation. Those fossils were thought to be A. fragilis until a few years ago.
What are some Other Names for Allosaurus?
Sometimes paleontology has multiple names for the same dino. This happens when many paleontologists name their fossil finds. Antrodemus is one of the common synonyms for Allosaurus.
The Allosaurus has had several names since they were first discovered in the late 1800s. They’ve been called:
- Antrodemus
- Apatodon
- Creosaurus
- Epanterias
- Labrosaurus
- Madsenius
- Wyomingraptor
Who are Big Al and Big Al Two?
Big Al is a subadult Allosaurus discovered in 1991. Big Al is 95% finalized and was the best Allosaurus fossil at the time. Big Al Two was discovered in 1996 and is one of the most complete dinosauria fossils ever found!
Big Al and Big Al Two gave paleontologists a glimpse into the life of Allosauruses. Both these dinos had healed fractures, signs of bone infection, and other injuries. These details help scientists learn more about dinos than partial skeletons can.
What State is Allosaurus the State Fossil of?
The Allosaurus is Utah’s state fossil. Allo was one of the most common predators found in Utah’s Cleveland-Lloyd Dinosaur Quarry. As of 2020, over 50 Allosaurus fossils were found in this area.
The Allosaurus was a fascinating Jurassic dinosaur of North America. Many of the over 100 fossils found are on display at The Natural History Museum of Utah.