The natural world is full of oddities. From the largest creatures to the smallest microbes, the Earth is full of extraordinary animals, people and things. This principle was no different during the time of the dinosaurs, when the world was populated with weird and wonderful creatures. In a series of articles over the next month, I will share my top picks for the most peculiar dinosaurs known to science and talk about what exactly made them so odd….
South America was considered to be a paleontological “black hole” for years largely due to lack of exploration, a dearth of trained paleontologists working in the region, and frankly, low interest from European and North American paleontologists. That was until a young Argentinian by the name of José Bonaparte shattered that notion almost single handedly. Bonaparte inspired a new wave of paleontological discoveries in South America, which have yielded fossils of not only some of the largest and earliest dinosaurs, but also some of the strangest. One of the oddest species of theropod dinosaurs, Carnotaurus, is amongst these peculiar finds.
As the title implies, the name Carnotaurus means ‘meat eating bull’, due to the pair of horns atop Carnotaurus’ skull. While horns amongst dinosaurs are typically restricted to the ceratopsians (see previous article), Carnotaurus seems to be an exception. The functions of these horns have been long debated, with a variety of theories coming forward. The first proposed idea is that the horns were simply used to attract mates, allowing each animal to recognize its own species. Other opinions have portrayed the horns as much deadlier weapons, being used as battering rams to battle members of its own species or as tools to dispatch potential prey animals. However this theory seems unlikely, as recent studies done on the skull of Carnotaurus show it would not have been able to take rapid blows to its skull. Nonetheless, the horns of Carnotaurus certainly give it a unique appearance amongst carnivorous dinosaurs.
The arms of Carnotaurus are even more pathetic than that of T-Rex! While the arms of Tyrannosaurus possessed sharp claws that could have hold and slash prey animals, the arms of Carnotaurus are smaller and less equipped than those of Tyrannosaurus. The arms bent backwards and did not have any claws, thus rendering them useless. Additionally, while most carnivores possessed three fingers, or in the case of the Tyrannosaurids two, Carnotaurus had four for unknown reasons. The reasoning for the tiny arms is that Carnotaurus simply didn’t need to use them, meaning there was no reason for them to grow to a large size.
The horns weren’t the only unique feature that Carnotaurus possessed amongst theropods. When Carnotaurus was found, the skeleton had large patches of skin preserved, some of which contain small bones called “osteoderms”. The function of these osteoderms was to act as armor, protecting Carnotaurus from attack. Like the horns, osteoderms can be found on other dinosaurs, mainly the Ankylosaurids, but are unique to Carnotaurus amongst theropod dinosaurs.
The final odd feature of Carnotaurus was its speed. Carnotaurus possessed an extremely large pelvic (hip) muscle, known as the caudofemoralis. Amongst theropods, Carnotaurus possessed the largest recorded caudofemoralis in relation to body size, with an estimated mass of about 111-137 kg (245-302 Ibs) each. Most people weigh less than this! This muscle was key to movement for dinosaurs and having such a large one would have led to a higher speed. The estimated speed of Carnotaurus is anywhere from 48-56 kilometres per hour (30-35 miles), which would have been one of the fastest speeds amongst all dinosaurs (only the ostrich-like Ornithomimids can top Carnotaurus)
So, there was an armored meat-eating dinosaur that had horns on its head, arms smaller than that of T-Rex and could also run like the wind? It does seem pretty outlandish to even suggest that such a creature could exist. However, there are plenty of more dinosaurs to come as part of weird dinosaur month that are just as odd.
Header image courtesy of Keller Pyle, found here
Gerardo V. Mazzetta, Adrián P. Cisilino, R. Ernesto Blanco, and Néstor Calvo “Cranial Mechanics and Functional Interpretation of the Horned Carnivorous Dinosaur Carnotaurus sastrei,” https://doi.org/10.1671/039.029.0313
Scott Persons and Phil Currie, “Dinosaur Speed Demon: The Caudal Musculature of Carnotaurus sastrei and Implications for the Evolution of South American Abelisaurids” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197156/
Steven Stanley, “Evidence that the arms of Tyrannosaurus rex were not functionless but adapted for vicious slashing” ://gsa.confex.com/gsa/2017AM/webprogram/Paper297346.html
“Predatory dinosaur was fearsomely fast”, https://www.cbc.ca/news/technology/predatory-dinosaur-was-fearsomely-fast-1.1064092
“Dinosauria Carnotaurus statue by slideshow collectible”, https://www.sideshow.com/collectibles/dinosauria-carnotaurus-sideshow-collectibles-2000163