Everyone knows Carnotaurus
(Fig. 1; Bonaparte 1985, Bonaparte, Novas and Coria 1990), the slender theropod with skull horns. In the large reptile tree (LRT, 1391 taxa) Carnotaurus nests with Majungasaurus, members of the first clade of giant theropods, the one that includes Spinosaurus, Allosaurus, Ceratosaurus and many others.
That comes as no surprise.
The only contribution I can make to this popular dinosaur is to note the horns arise from laterally extended lacrimals and prefrontals, not laterally extended frontals, as originally proposed (Fig. 1). In stating this, I may be late to the party. If others have already published on this bit of trivia, I am not aware of it. If so, let me know.
Carnotaurus sastrei (Bonaparte 1985; Bonaparte, Novas and Coria 1990; Late Cretaceous, 70 mya; 7.5m in length) is an abelisaurid theropod dinosaur related to Majungasaurus. Carnotaurus had a shorter, upturned snout, a shorter mandible, frontal horns, a deeper jugal, a narrower skull (below the horns) and a down-turned naris.
Bonaparte JF 1985. A horned Cretaceous carnosaur from Patagonia. National Geographic Research. 1 (1): 149–151.
Bonaparte JF, Novas FE and Coria RA 1990. Carnotaurus sastrei Bonaparte, the horned, lightly built carnosaur from the Middle Cretaceous of Patagonia. Contributions in Science. 416: 1–41. PDF