Allosaurus

A. amplexus, A. atrox, A. fragilis, "A. jimmadseni", and A. maximus are all known from remains discovered in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across the states of Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming. A. fragilis is regarded as the most common, known from the remains of at least sixty individuals.[13] Debate has gone on since the 1980s regarding the possibility that there are two common Morrison Formation species of Allosaurus, with the second known as A. atrox;[8][61] recent work has followed a "one species" interpretation,[13] with the differences seen in the Morrison Formation material attributed to individual variation.[62][63] A. europaeus was found in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation,[60] but may be the same as A. fragilis.[64] A. tendagurensis was found in Kimmeridgian-age rocks of Tendaguru, in Mtwara, Tanzania.[65] Although the most recent review tentatively accepted it as a valid species of Allosaurus, it may be a more basal tetanuran,[66] or simply a dubious theropod.[1] Although obscure, it was a large theropod, possibly around 10 meters long (33 ft) and 2.5 metric tons (2.8 short tons) in weight.[2]