Carnotaurus — The Horned Predator With Arms Smaller Than Your Hand

When and where

Carnotaurus lived from 72 to 69 million years ago in what is now Chubut Province, Argentina. The fossils come from the La Colonia Formation, rocks laid down on a coastal plain during the Late Cretaceous. The climate was warm and seasonal, with river channels cutting through mudflats. South America was an island continent at the time, separated from North America and Antarctica by shallow seas. Turtles, crocodiles, and other large abelisaurids lived in the same ecosystem, which means Carnotaurus shared its habitat with rival predators.

How we know

Paleontologist José F. Bonaparte discovered the skeleton in 1984. It was nearly complete, a rare find for a large theropod. Bonaparte described it in 1985 and named it Carnotaurus sastrei: "meat-eating bull", with the species name honouring Angel Sastre, the owner of the ranch where it was found. The specimen preserves skin impressions across parts of the body, the only direct evidence we have of abelisaurid skin texture. The animal carried rough, pebbly scales and no feathers. The Wikipedia article on Carnotaurus covers the anatomy in more detail.

What set it apart

Carnotaurus was around 8 metres long and weighed close to 1.5 tonnes. Two thick horns sat above the eyes, the only confirmed horns on any large carnivorous dinosaur. The neck was broad and muscled, built for pulling and gripping. The forelimbs were drastically reduced, even shorter than those of Tyrannosaurus rex, with immobile fingers and no claws. The skull was short and deep, giving it a bulldog-like profile very different from the elongated snouts of carcharodontosaurids or tyrannosaurids. The jaw could open unusually wide, and the teeth were slender, built for slicing rather than crushing. Muscle and tail studies suggest it could run fast, likely the fastest large theropod for which we have good evidence.

For collectors and classrooms

A Carnotaurus model is useful for showing students how predators can look nothing alike. Hold it next to a T. rex model: two giant theropods, two completely different solutions. The horns above the eyes and the stubby forelimbs are the details to check in a quality figurine. Cheaper toys often miss the horns or give it long arms by mistake. You can find a hand-painted Carnotaurus figurine here.