Long-time readers of Impurest’s Guide to Animals (IGTA) may remember a special one off issue I wrote regarding the dromaeosaur Balaur bondoc. As it often does however, science marches on and Balaur was reclassified from dinosaur to flightless bird, meaning we are in need of a replacement ‘terrible lizard’. Happily I found such a creature, one that’s fast, mean and very interesting. Hope you guys enjoy.
Issue #170 - Carnotaurus sastrei
Kingdom – Animalia
Phylum – Chordata
Class – Reptilia
Order – Saurischia
Family – Abelisauridae
Genus – Carnotaurus
Species – sastrei
Related Species - Carnotaurus is one of the Abelisaurs, a group of medium to large carnivorous dinosaurs predominantly from the Cretaceous Period.
Range - The remains of Carnotaurus have only been found in the La Colonia Formation in Argentina
Not a Flightless Bird!
Carnotaurus was a large therapod dinosaur (about 8m in length and just over 1250kg in weight) that lived in the Late Cretaceous Period between 72 and 68 million years ago (1). Like most large therapods, Carnotaurus had a large powerful head and short arms, in the case of this species and its relatives the forelimbs were virtually vestigial, being shorter than those found in Tyrannosaurus rex. While many dinosaurs, including some of the larger therapods, are now considered to have down or feathers covering their body, traces of the skin of Carnotaurus was fossilised, and seems to be covered in a mosaic of small scales and thorn like scutes running down the back and flanks (2). The most defining feature of this dinosaur however, where the two bull like horns on the animals forehead, something that leaded itself to the naming of this species, with Carnotaurus literally translating from Latin as ‘Meat Eating Bull’.
Like the vast majority of the large therapods Carnotaurus was a carnivore, using the long and slender teeth in its jaws to deliver quick bites to its prey. To aid it in capturing its victims, Carnotaurus’s jaw was hinged in a manner akin to snakes, allowing it change the orientation that its attacks struck from, allowing it to adjust its bite to pin prey or to force it back into its throat. Prey was likely ran down from an ambush position, with the leg structure of the species suggesting that the bones were designed to withstand high bending pressures and that the muscle on the femur was likely considerably larger than other therapods of equal or greater size (3), both signs of a powerful and fast runner, with a maximum speed of 35 miles an hour estimated. All these factors suggest that Carnotaurus was predominantly a hunter of small game, although it probably included larger animals in its diet when the opportunity presented itself.
Despite early hypothesis that Carnotaurus gored its prey with its horns, it is more likely that the dinosaur used them in sexual selection. Suggestions that Carnotaurus butted heads over territory or mating rights has some credibility since the skull of the animal is shortened and partially reinforced to withstand high speed impacts, although this could also be a trait to protect the cranial organs from the crashes that come from a high speed lifestyle. Far more likely is that the animals gently placed heads together before pushing against each other to determine each other’s strength in a relatively non-violent way (4). While no eggs of Carnotaurus have been discovered, studies of the bones of the closely related Majungasaurus crenatissimus suggested that all the Abelisaurs were slow growers, taking many years to reach sexual maturity (5).
Impurest Cheese: Urban Legend Quashers #3 - Dilophosaurus
Statement:Dilophosaurus, you mean that ‘little spitter’ from Jurassic Park. Man that thing is creepy, that noise and the frill thing really make it unique among the dinosaurs in that film.
Fact: Ah well the Dilophosaurus in both the novel and film of Jurassic Park added a lot of features that the actual dinosaur didn’t have. For example while the Dilophosaurus in the film is about four to seven foot (approx.) in length, the actual animal was probably just shy of seven meters in length and half a ton in weight.
Statement: Oh wow not so little then! How about the spitting venom thing, could it do that then?
Fact: I suspect not. Being venomous doesn’t fossilise unfortunately, but considering that Dilophosaurus was the largest carnivore of its day, I strongly suspect that it being venomous was an invention of Michael Crichton (and should have been explained in book as being down to the DNA code being filled in with the genetic structure of a Rinkhals Cobra (Hemachatus haemachatus)
Statement: Uhm the frill then? Surely that would fossilize…
Fact: Elements of it would, and since we have no proof of that I suspect Dilophosaurus made do without it. In fact I suspect that we can blame this feature on Steven Spielberg, since the feature was not in the book, and was likely based on the ‘frill’ of the Frilled Necked Lizard (Chlamydosaurus kingii)
Statement: Is anything correct? Did it even have those crests on its head?
Fact: Those are indeed accurate and were likely used in sexual competition between males for breeding rights. They may have also been combined with brightly coloured feathers since its probable that most (but not all) therapods had some kind of down covering their bodies.
Statement: Thanks I guess. You must hate Jurassic Park judging by how easily you ripped that cute ‘little spitter’ apart
Fact: Wrong again, I love it ;-)
1 -Bonaparte, José F. (1996). "Cretaceous tetrapods of Argentina". Münchener Geowissenschaftliche Abhandlung. A (30): 89
2 - Czerkas, Stephen A.; Czerkas, Sylvia J. (1997). "The Integument and Life Restoration of Carnotaurus". In Wolberg, D. I.; Stump, E.; Rosenberg, G. D. Dinofest International. Academy of Natural Sciences, Philadelphia. pp. 155–158
3 - Persons, W. S.; Currie, P. J. (2011). Farke, Andrew Allen, ed."Dinosaur Speed Demon: The caudal musculature ofCarnotaurus sastreiand implications for the evolution of South American abelisaurids".PLoS ONE.6(10): e25763
4 - Mazzetta, Gerardo V.; Cisilino, Adrián P.; Blanco, R. Ernesto; Calvo, Néstor (2009). "Cranial mechanics and functional interpretation of the horned carnivorous dinosaur Carnotaurus sastrei". Journal of Vertebrate Paleontology. 29 (3): 822–830.
5 - http://www.livescience.com/56897-slow-growing-theropod-dinosaur.html
1 - http://images.dinosaurpictures.org/carnotaurus_096a.jpg
2 - http://www.praha.eu/public/b/3f/68/115037_4_chlupacovo_muzeum_kostra.jpg
4 - http://vignette1.wikia.nocookie.net/jurassicpark/images/b/b0/Dilophosaurus.gif/revision/latest?cb=20150305184526
There we have it, I dare science to tell me this is just a flightless bird. Anyway I’d like to say normal service will be restored next week, but to lie to yew would be totally toxic. Until then though make sure to critic, comment and suggest future issues as well as making sure you check out past issues in Impurest’s Bestiary