October 17. Ceratosaurus

Ceratosaurs were late Jurassic carnivorous dinosaurs that lived at least in western North America and in Portugal, two places where its fossils have been found. It was around 20 to 25 feet long and had a pretty typical dinosaurian shape, but with several horns on its snout and head. Its name means “horned lizard.”

The first specimens were discovered in 1884 and described by O.C. Marsh, a paleontologist who explored the western United States. He was prolific in his fossil collecting. His discovery of Ceratosaurus came in the midst of the Bone Wars – the intense competition between Marsh and Edward Drinker Cope, a personal animosity that spilled over into their professional lives. Many books address this battle, which was also a time when vast numbers of dinosaur fossils were discovered.  

Technically, Ceratosaurus is a genus of the larger group of ceratosauria, whose fossils have been found in North and South America, Europe, Africa, and Madagascar. There may be three species of Ceratosaurus, but it’s not completely agreed that that’s the case. It’s possible that some of the fossils assigned to different species, such as the ones found in Portugal, may be variations in a single species due to age or simply to individual variation.

The first known ceratosaurs date to about 225 million years ago, the late Triassic, but it was during the Jurassic that they diversified significantly. Ceratosaurus nasicornis – meaning “horned lizard with a nose horn” – was the one described by Marsh from Late Jurassic sediments, and it’s the largest ceratosaur known at 20 or more feet long.

Modern Ceratosaurus reconstruction drawing by DiBgd at en.wikipedia used under CC-BY-2.5

Ceratosaurs were theropods, a large diverse group of dinosaurs that were bipedal, though not necessarily with the upright stance that has traditionally been depicted. More likely, the body was carried more close to a horizontal position with respect to the ground. Marsh’s drawings of dozens of dinosaurs, many of them published in USGS Annual Report Volume 16 part 2, Dinosaurs of North America, showed the upright orientation, leading to reconstructions in museums that have continued that tradition. Today, better understanding of the ways the hip and leg bones worked has led to the view that they carried themselves on two legs, but more level with the ground.

Theropods include dinosaurs that had feathers, as well as all birds. Ceratosaurus was in a different branch of theropods – closer to birds than crocodilians, but not all that close.

—Richard I. Gibson

Modern reconstruction drawing by DiBgd at en.wikipedia used under CC-BY-2.5 

Ceratosaurus as a tattoo  (YouTube)