The story
Allosaurus fragilis, named by Othniel Charles Marsh in 1877, was the dominant large predator of the Late Jurassic Morrison Formation. Adults averaged about 8.5 m and reached about 9.7 m, with a deep, narrow skull, serrated blade-like teeth and three-fingered clawed hands. Its jaws could slash downward like a hatchet, an idea supported by a 2001 skull stress study by Emily Rayfield and colleagues. It hunted young sauropods and plated Stegosaurus. A typical adult weighed about 2 tonnes, and like other theropods it replaced worn teeth continuously throughout life.
The Cleveland-Lloyd Dinosaur Quarry in Utah has yielded the bones of at least 46 Allosaurus of different ages, one of the largest accumulations of any big predator. Another famous specimen, Big Al from Wyoming, found in 1991, shows 19 injured or infected bones, a reminder of how hard such lives were. Allosaurus is the namesake of the Allosauroidea, and its relatives lived until the Cretaceous.
Why it mattered
- Allosaurus gives a model of how a large theropod hunted in a world of giant plant eaters.
- Its bone beds record unusual events, such as droughts or predator traps, on the Morrison plains.
- Its relatives spread worldwide, leading toward large Cretaceous predators like Carcharodontosaurus.
Sources
- Allosaurus Natural History Museum
- New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda) based on another specimen with multiple pathologies PeerJ
- Jurassic National Monument: Learn and Explore Bureau of Land Management
Community notes
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