TYPE SPECIES:
• A. fragilis Marsh, 1877 "fragile different lizard"
  OTHER SPECIES:
• A. amplexus (Cope, 1878) [nomen dubium?] (originally Epanterias)
• A. maximus Chure, 1995 "greatest different lizard"
• A. sp.
• ?A. tendagurensis Janensch, 1925 [nomen dubium] "different lizard from the Tendaguru Formation"
• A. trihedrodon (Cope, 1877) [nomen dubium] (originally "Laelaps") "different lizard of the three-sided tooth"
• A. whitei Pickering, 1995 [nomen nudum]
  
  MISASSIGNED SPECIES:
• A. atrox (Marsh, 1878) (originally Creosaurus) ==
• A. ferox Marsh, 1896 "fierce different lizard" ==
• A. lucaris Marsh, 1878 == A. fragilis
• A. medius Cope, 1888 [nomen dubium] = Dryptosaurus medius
• A. meriani == Ceratosaurus meriani
• A. sibiricus (Riabinin, 1914) [nomen dubium] (originally Antrodemus) = Chilantaisaurus sibiricus
• "A." sp. » Tetanurae incertae sedis
• A. valens (Leidy, 1870) [nomen dubium] (originally Poekilopleuron) = Antrodemus valens

Animalia
Vertebrata
Tetrapoda
Sauropsida
Archosauromorpha
Ornithodira
Dinosauria
Theropoda
Tetanurae
Carnosauria
Allosauridae

• A. fragilis: 10 m to 12 m
• A. maximus: ?14 m
• "A." sp.: 5 m to 6 m

• A. fragilis: 1 tonne to 1.7 tonnes
• A. amplexus: 3 tonnes to 5 tonnes

One of the most famous and popular dinosaurs, Allosaurus is known primarily from the Morrison Formation. It probably hunted stegosaurs, iguanodonts, and perhaps gigantic neosauropods like Diplodocus and Camarasaurus. Its main rival was the slightly smaller Ceratosaurus.

There is debate over the taxonomy of these species. Some feel that most of them should be lumped into A. fragilis while others would split them into several genera (Creosaurus, Epanterias, Saurophaganax, etc.)

   left foreground, small: Othnielia
   left foreground, large: Stegosaurus
   left midground (pair): Camarasaurus
   right foreground: Dryosaurus
   right background (pair): Allosaurus
   in the air: rhamphorhynchids
  

I.   Alectrosaurus olseni
II.  Acrocanthosaurus atokensis
III. Alioramus remotus
IV.  Allosaurus fragilis