This large predatory dinosaur had a thick, powerful neck, a bull-shaped head and very short forearms for its size.
Carnotaurus was previously considered to be a member of the group of dinosaurs known as the carnosaurs. However, the group has since been defined to encompass only the allosaurs and their closest kin. It is now classified as an abelisaurid. Carnotaurus had a shorter and deeper skull than Tyrannosaurus and had hornlets over its eyes.
An almost complete skeleton of Carnotaurus was extracted with difficulty from the hard mineral nodule in which it was preserved in Argentina. The deep skull suggests that it may have had an acute sense of smell, but the strength of the jaws and neck implied by the muscle attachments seem at odds with the weakness of the lower jaw and teeth.
Name: Carnotaurus, meaning ‘meat-eating bull’
Size: 7.5m long and 3.5m high
Food: meat, mainly other dinosaurs
Lived: 100-90 million years ago in the Middle to Late Cretaceous in South America
The head is very short and squashed-looking, with a shallow, hooked lower jaw. Two horns stick out sideways from above the eyes, probably being used for sparring with rivals. The arms are extremely short with no apparent forearms, even shorter than the tiny arms of Tyrannosaurus. They form mere stumps with four miniscule fingers. The skin texture, the best-known of any theropod, has a groundmass of small, pebbly scales but with large, conical scutes forming rows along the sides.
The skull of Carnotaurus has an enormous hole in front of the eye sockets – this is known as the antorbital fossa. All theropods possess this, but only in the abelisaurids is it so large.
Its long, muscular hind legs may have made Carnotaurus much more agile than some other theropods. It would have been able to rush up on its prey and take it by surprise, probably using its sharp claws to slash and grip, while its powerful jaws took out chunks of flesh.
Although Carnotaurus had a very strong skull, it also needed to be light enough to move easily. There were spaces in the sides of the skull to help make it lighter. By jerking its head back, Carnotaurus could tear its prey apart. The teeth in the upper jaw could slice through the flesh, which was held by the lower jaw. Carnotaurus had teeth about 4cm long which curved backwards to help it keep hold of its victim.
Carnotaurus was found in a vast area of grassland and semi-desert called Patagonia in Argentina in 1985. It was an exciting find because the remains gave scientists a very good idea of what this dinosaur’s skin looked like. Along the surface of the body, from head to tail, there were rows of cone-shaped bumps. Rows of big, raised sclaes stood out from the smaller bumps on Carnotaurus’ head, making a pattern around the eyes and on the upper part of its snout.
Carnotaurus was as heavy as a car, almost as tall as an elephant and ran on two legs. Its long backbone was like a big girder supporting the weight beneath. Long rib bones from shoulder to hip gave Carnotaurus extra protection and support.
When Carnotaurus was moving at top speed it would have been unstable without its tail. Carnotaurus used its long, muscular tail to help it keep its balance. This enabled it to push its head forward to seize hold of its struggling prey.
At the top of its short deep head, Carnotaurus had a pair of small, flat horns. These jutted forward over its eyes rather like little wings. Unlike the ceratopsians, such as Triceratops, Carnotaurus’ horns were too small to have been used for defence. Experts think that they may have been coated in extra layers of horn, which would have made them longer. Like stag deer, it is also possible that the male Carnotaurus had larger horns than the females.