big gapes

Allosaurus () is an extinct genus of large theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period (Kimmeridgian to late Tithonian ages). The name "Allosaurus" means "different lizard", alluding to its unique (at the time of its discovery) concave vertebrae. The first fossil remains that could definitively be ascribed to this genus were described in 1877 by Othniel Charles Marsh. The genus has a very complicated taxonomy and includes at least three valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America's Morrison Formation, with material also known from the Alcobaça Formation and Lourinhã Formation in Portugal with teeth known from Germany. It was known for over half of the 20th century as Antrodemus, but a study of the abundant remains from the Cleveland-Lloyd Dinosaur Quarry returned the name "Allosaurus" to prominence. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.
Allosaurus was a large bipedal predator for its time. Its skull was light, robust, and equipped with dozens of sharp, serrated teeth. It averaged 8.5 meters (28 ft) in length for A. fragilis, with the largest specimens estimated as being 9.7 meters (32 ft) long. Relative to the large and powerful legs, its three-fingered hands were small and the body was balanced by a long, muscular tail. It is classified in the family Allosauridae. As the most abundant large predator of the Morrison Formation, Allosaurus was at the top of the food chain and probably preyed on large herbivorous dinosaurs such as ornithopods, stegosaurids, and sauropods. It is also possible that it hunted other predators. Scientists have debated whether Allosaurus had cooperative social behavior and hunted in packs or was a solitary predator that form congregations, with evidence supporting either side.

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