Allosaurus fragilis

Overview

Allosaurus fragilis is a large carnivorous dinosaur from Late Jurassic North America. It is characterized by a tooth-lined skull, three-fingered forelimbs, and a long tail. It was a predator in a world far older than that of Tyrannosaurus.^[1][2][3]

Key facts

Fossils are not always preserved flattened. One Allosaurus skull from the Carnegie Quarry retained its three-dimensional form particularly well. Differences in the sediment surrounding buried remains affected the body forms we can see today.^[2]

Time and place

It lived in the region of present-day North America during the Late Jurassic, around 150 million years ago. It is one of the representative carnivorous dinosaurs of the Morrison Formation in the USA. Bones of several contemporary dinosaurs were found at the Carnegie Quarry.^[1][2]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

Museum accounts give a body length of approximately 9.7 m for the genus Allosaurus. It supported its body on two legs, with a long tail extending behind. Its hands had three fingers, and rows of serrated teeth lined the mouth.^[1][3][2]

Habitat and reproduction

It was a carnivore with serrated teeth. US National Park Service material describes juveniles as having relatively long legs. Changing body proportions during growth invite questions about changes in movement and feeding.^[2]

Fossil discovery

The well-preserved Carnegie Quarry skull became an actual fossil display that could be examined in detail. A detailed study of the forelimbs was also published in 1915. Comparisons of the head and hands helped reveal this predator’s body.^[2][3]

References

1. Allosaurus
2. National Park Service — Allosaurus fragilis
3. Gilmore1915 — The forelimb of Allosaurus
4. Natural History Museum — Tyrannosaurus
5. Natural History Museum — Allosaurus
6. National Park Service — Allosaurus fragilis
7. Stegosaurus
8. Gilmore1915 — The forelimb of Allosaurus

Research questions

Did carnivorous dinosaurs retain the same appearance and way of life as they grew? Researchers compare head and limb proportions across specimens of different sizes. Examining how bones accumulated and were buried in one rock layer also provides a starting point for studying ancient ecology.^[2]

Observation

After examining the skull and serrated teeth, find the three fingers on the short forelimbs. Continue to the long hind legs and tail to see the overall proportions of a bipedal predator.^[1][3]