Carnotaurus sastrei
Carnotaurus is an abelisaurid — the carnivorous dinosaurs that succeeded the carcharodontosaurids and bossed Late Cretaceous South American ecosystems like tyrannosaurids did in the North — and being the first of its clan to be known from relatively complete remains it did a sterling job of showcasing their weird features.
Abelisaurids' comically stumpy arms, attached to massive shoulder blades, were nothing more than wrists with a couple of fused, clawless fingers, and at least one paleontologist has toyed with the theory that they may have been weapons of mass seduction to tickle the backs of a mate during, well, mating. They also had a short and high skull, but Carnotaurus looked like it had suffered a particularly high fall from the ugly tree, hit every branch on the way down then landed face first, on an anvil. It had two huge, gnarly name-prompting horns above its eyes too. But it's not all bad news.
The eyes of Carnotaurus face fully forward which hints at binocular vision, and scientists recently realised that it had the largest "caudofemoralis" muscle of any land-dwelling animal ever, relative to body size. Supported by pairs of interlocking rib-like bones along the underside of its tail and attached by a tendon to a finger-like nub of bone (fourth trochanter) on the rear of each upper leg bone (thigh), this muscle was a power pack for explosive acceleration, but it came at a cost. Unfortunately, the tail-stiffening bone structure resulted in a loss of manoeuvrability and hampered quick, fluid turns, but for straight ahead A to B hunting there was no swifter large theropod dinosaur.
An unusually slim lower jaw compared to the extremely deep skull to which it was attached raised questions about its feeding habits that so far no-one has been able to answer. But what we can be sure of, thanks to preserved skin impressions, is that Carnotaurus bucked what had become something of a trend with recent discoveries of our filament or fluff-adorned friends by being a theropod dinosaur that definitely wasn't feathered... at least on the parts that the skin impressions belong to.
The species epithet, sastrei, honors Don Angel Sastre - owner of the farm/ranch where its remains were discovered.
