Allosaurus

Allosaurus fragilis was the apex predator of Late Jurassic North America, a powerful theropod built for active hunting. With a massive skull armed with dozens of serrated, blade-like teeth and powerful three-fingered arms tipped with sharp claws, it was superbly equipped to take down the giant sauropods and stegosaurs that shared its world. Its name, meaning "different lizard," refers to the distinctive hollowed-out vertebrae that made its skeleton surprisingly lightweight for its size.

Allosaurus holds a special place in paleontology as one of the best-understood large theropods thanks to an extraordinary abundance of fossil material. The Cleveland-Lloyd Dinosaur Quarry in Utah alone has yielded remains from at least 46 individual Allosaurus, ranging from juveniles to full-grown adults. This wealth of specimens has allowed scientists to study its growth patterns, individual variation, and even pathologies — including healed injuries that tell stories of violent lives.

The genus was first described by Othniel Charles Marsh in 1877 during the "Bone Wars," the famous rivalry between Marsh and Edward Drinker Cope that unearthed so many American dinosaurs. For much of the 20th century, the name Antrodemus was mistakenly used for this animal, but detailed study of the Cleveland-Lloyd material in the 1970s restored Allosaurus to its rightful prominence.

Beyond North America's Morrison Formation, Allosaurus fossils have been found in Portugal, suggesting these predators ranged across a much larger territory when shallow seas didn't separate the continents. Some specimens show evidence of infected bite wounds, broken ribs, and stress fractures — testament to the dangerous business of being a Jurassic apex predator.