Marshosaurus ‭(‬Marsh’s lizard‭)

Short Info

Marshosaurus ‭(‬Marsh’s lizard‭)

Phonetic : Marsh-o-sore-us.

Named By : James Madsen‭ ‬-‭ ‬1976

Diet : Carnivore

Size : Estimated 5 – 6 meters long

Type of Dinosaur : Large Theropod

Type Species : M.‭ ‬bicentesimus‭ (‬type‭)

Found in : USA – Utah,‭ ‬Colorado‭ ‬-‭ ‬Morrison Formation

When it Lived : Late Jurassic, 154-142 million years ago

Marshosaurus is a medium-sized, carnivorous, theropod dinosaur genus that belonged to the Megalosauroidea. It was found in the Late Jurassic Morrison Formation, Utah, and possibly Colorado.


Marshosaurus bicentissimus skull cast - Natural History Museum of Utah - DSC07218Daderot, CC0, via Wikimedia Commons


Marshosaurus was a medium-sized theropod. Gregory S. Paul, in 2010, estimated that Marshosaurus was 4.5m (15 ft) long and weighed 200 kg (440 lb). The length of the holotype Ilium is 37.5 cm (14.8 in). The skull measured approximately 60 cm (24 in) long, if the cranial material was correctly referred to.

Matthew Carrano, an autapomorphy was established in 2012 by the holotype. The suture connecting the pubic bones and the pubic peduncle is convex and curves upwards at the front, and concave at its rear.

Over 14000 fossil bones were discovered at the Cleveland-Lloyd Quarry, central Utah, in the 1960s. While the majority belonged to Allosaurus, some bones were from at least two new theropods. James Henry Madsen Jr. named one of these as the genus Stokesosaurus in 1974.

Madsen gave the type species Marshosaurus bicentensimus the name Marshosaurus bicentensimus in 1976. Professor Othniel Marsh, a nineteenth-century paleontologist who discovered many dinosaur fossils during Bone Wars, was the generic name. This name was chosen in honor of the United States’ bicentennial.

The holotype, UMNH VP 6373 was found in a layer from the Morrison Formation’s Brushy Basin Member. It dates back to the late Kimmeridgian (around 155 – 152 Mya). It is the left ilium or upper pelvis bone. Paratypes were composed of three bones: the pubic bone UMNH VP 6387, the ischia UMNH VP 6379, and the UMNH VP 380. Provisionally, three ilia and six fragments of the jaw were referred. This material is representative of at least three individuals.

Brooks Britt refereed tail vertebrae from Colorado in 1991 because they were similar to non-identified fragments of tail vertebrae from the Cleveland-Lloyd Dinosaur Quarry. A 1993 partial skeleton (CMNH 21704) from Dinosaur National Monument, was referred to because its dorsal neuro spines resembled those of the Cleveland-Lloyd Dinosaur Quarry. The 1997 SVP abstract also included this specimen.

Source: Wikipedia