About Carnotaurus
| Scientific Name (Genus) | Carnotaurus |
| Meaning of Name |
Meat-eating bull
carō(meat)[Latin]-taurus(bull)[Latin] |
| Classification | Saurischia, Theropoda (Abelisauridae, Carnotaurini) |
| Total Length | 7.5 - 8m |
| Diet | Carnivorous |
| Period | Late Cretaceous (approx. 69 - 66 million years ago) |
| Sub-classification / Species Name | Carnotaurus sastrei |
| Year of Paper Publication | 1985 |
| Genus Name Publication |
A horned Cretaceous carnosaur from Patagonia.
National Geographic Research. 1 by Bonaparte, José F. 1985. |
Features
Carnotaurus is a large theropod that lived on the South American continent during the Maastrichtian stage (about 69 to 66 million years ago), the very end of the Late Cretaceous. Estimated at 7.5 to 8 meters long and weighing 1.3 to 2.1 tons, it was an apex predator in the ecosystem of the Southern Hemisphere at the time.
The most iconic features of Carnotaurus are a pair of robust horns growing upward from above its eyes (frontal bones) and its extremely reduced, short forelimbs.
These horns are compressed flat from top to bottom, reaching about 14.6 cm in length, with numerous vertical groove-like decorations on their surface. While the exact purpose of the horns is not fully understood, they are believed to have been used for display or in combat between conspecifics.
Internal structure and evolution of the horns: Recent CT scan analysis of the internal structure revealed that while the horns are essentially solid bone inside, there are small cavities (pneumatic fossae) at the base of each horn. This is highly likely anatomically related to the cavity of the lacrimal bone (the bone in front of the eye), and is evaluated as a feature similar to the evolution of lightening the skull (pneumatization) seen in Majungasaurus and Ceratosaurus.
The skull had a unique shape, being shorter from front to back and deeper from top to bottom compared to other theropods. It was once thought that because of the few joints in the lower jaw bone, it was "fragile and had a weak bite force," but recent research has revealed that this was an evolution to provide the entire jaw joint with a high degree of flexibility. It is speculated that it adapted to a hunting style that helped it swallow prey whole by flexibly expanding its jaws like a snake, or causing bleeding by slashing prey like a Komodo dragon.
Hatchet bite hypothesis: Carnotaurus had developed extremely thick and robust neck muscles instead of its reduced, useless forelimbs. This theory suggests that it specialized in a tactic of using its strong neck to swing its short, deep skull down like a hatchet, inflicting deep wounds on its prey.
Its forelimbs were much shorter than those of Tyrannosaurus, with unossified wrist bones and completely fused finger joints. It is known that they were "vestigial organs" that had completely lost any practical function for catching or manipulating prey.
Carnotaurus is also famous for being the first theropod in history to have extensive "fossilized skin" preserved. There were no traces of feathers; instead, large and small conical scales were arranged in a mosaic pattern. Recent research suggests that this highly uneven skin structure was not merely armor, but served as a "radiator (thermoregulation)" to efficiently release excess body heat generated by intense exercise.
Fast Runner of the Cretaceous
What surprised the world in the study of Carnotaurus was its extraordinary sprinting ability. The main power source of a dinosaur's hind legs is a muscle called the "caudofemoralis," which connects the base of the tail to the thigh.
A detailed examination of Carnotaurus's tail skeleton revealed a special structure where the ribs extending laterally from the tail slanted diagonally upward, and adjacent bones overlapped and locked together. This created a vast space in the lower part of the tail, allowing it to house one of the largest caudofemoralis muscles in history relative to its body size.
Driven by this maximized muscle engine, Carnotaurus is estimated to have been able to sprint at 48-56 km/h, undoubtedly one of the fastest speeds among large theropods. It was truly a "super high-speed predator." On the other hand, because the tail bones were locked together, the tail lost its flexibility, and its "agility" to make sharp turns while running was significantly reduced. It is thought to have excelled at hunting by chasing prey in a straight line on open coastal plains rather than in dense forests.
Discovery and Description
Source: On the palaeobiology of the South American horned theropod Carnotaurus sastrei Bonaparte.
by Mazzetta, Gerardo V.; Fariña, Richard A.; Vizcaíno, Sergio F. 1998.
Fossils of Carnotaurus were first discovered in 1984 on a farm called "Pocho Sastre" in Chubut Province, Argentina. The discovery was quite dramatic: Ángel Sastre, the farm owner's nephew, picked up an "oddly shaped stone" from the ground to throw at an unruly flock of sheep, which turned out to be a fossilized Carnotaurus vertebra.
Subsequently, an excavation team led by renowned paleontologist José Bonaparte rushed to the site and extracted a remarkable fossil from extremely hard rock, with about 80% of the skeleton preserved in articulation.
The following year, in 1985, Bonaparte published the paper "A horned Cretaceous carnosaur from Patagonia" and formally described it as a new genus and species, "Carnotaurus sastrei." The specific name "sastrei" was given in honor of the Sastre family, who made the initial discovery.
Expanding diversity: For a long time, it was thought that Carnotaurus was the only large predator in this formation (La Colonia Formation). However, in 2024, a new genus of hornless dinosaur, "Koleken," was discovered from the same formation. It is becoming clear that Abelisaurid dinosaurs prospered much more diversely than we imagined on the South American continent at the end of the Cretaceous.