Marshosaurus

Marshosaurus was a mid-sized theropod dinosaur unearthed from the prolific Cleveland-Lloyd Dinosaur Quarry in Utah, part of the Late Jurassic Morrison Formation. Reaching between four and five and a half metres in length, it was overshadowed in size by apex contemporaries like Allosaurus and Torvosaurus, likely occupying a secondary predator niche. Its skeletal remains, primarily consisting of ilia, jaw fragments, and vertebrae, reveal affinities with the megalosauroid radiation, specifically within the Piatnitzkysauridae. The pelvis displays distinctive features, including a low iliac blade. Paleopathologies on several recovered bones show evidence of healed fractures and infections, attesting to a physically demanding life. As an active carnivore, Marshosaurus would have pursued ornithopods like Dryosaurus or preyed upon smaller reptiles throughout the sprawling semi-arid floodplains of western North America.

Named to honour pioneering palaeontologist Othniel Charles Marsh during the United States Bicentennial in 1976.

Where and when

Marshosaurus lived in the Late Jurassic, from 154 to 150 million years ago (Kimmeridgian-Tithonian age). Its remains come from United States, in the Morrison Formation.

The numbers

Length 5 m (estimates run from 4.5 to 5.5 m). Mass about 280 kg. Hip height about 1.5 m. That is 2.9 human-lengths, or 0.45 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Marshosaurus with a bus Place on the timeline