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Name means: Othniel Charles Marsh’s Reptile


Species: bicentesimus

Range: Late Jurassic (Tithonian, 150-145 MYA) from Utah, possibly Colorado

Size estimate: 12-15 ft length, 1000-1200 lbs

Discovery: James Madsen, 1976

Classification: dinosauria, saurischia, therapoda, megalosauroidea, piatnitzkysauridae


The only certain Marshosaurus fossils come from the Cleveland-Lloyd Dinosaur Quarry near Price, Utah. Other finds at Dinosaur National Monument and from Colorado may belong to Marshosaurus. However, scientists know this species solely from the hip bones of a few individuals. The fossils from other locations did not include those hips. This makes their connection to Marshosaurus difficult to prove. Even so, the original hip bones present enough data to tell that Marshosaurus belongs to a group called megalosauroids. Torvosaurus and Baryonyx also belong to this group, making them distant cousins to Marshosaurus. Torvosaurus inspired the look of the Marshosaurus statue shown here. No one knows exactly what the living animal would have looked like, though. The original hip bones appear to belong to a fully-grown animal, so the species was probably medium-sized.


How Marshosaurus lived alongside better-known animals like Allosaurus or Apatosaurus remains unknown. It probably coexisted with larger fauna by hunting different prey or using special hunting tactics. It could have preferred a separate habitat, which may explain its rarity. Until scientists manage to find better skeletons, Marshosaurus will remain a tantalizing mystery.

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