Abelisauridae

Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian subcontinent and the island of Madagascar. Isolated teeth were found in the Late Jurassic of Portugal, and the Late Cretaceous genera Tarascosaurus and Arcovenator have been described in France. Abelisaurids first appear in the fossil record of the early middle Jurassic period, and at least three genera (the Moroccan Chenanisaurus, the South American Carnotaurus and the Madagascan Majungasaurus) survived until the end of the Mesozoic era 66 million years ago. Like most theropods, abelisaurids were carnivorous bipeds. They were characterized by stocky hind limbs and extensive ornamentation of the skull bones, with grooves and pits. In many abelisaurids, such as Carnotaurus, the forelimbs are vestigial, the skull is shorter, and bony crests grow above the eyes. Most of the known abelisaurids would have been between 5 and 9 m (17 to 30 ft) in length, from snout to tip of tail, with a new and as yet unnamed specimen from northwestern Turkana in Kenya, Africa reaching a possible length of 11–12 m (36 to 39 ft). Before becoming well known, fragmentary abelisaurid remains were occasionally misidentified as possible South American tyrannosaurids. Abelisaurid hind limbs were more typical of ceratosaurs, with the astragalus and calcaneum (upper ankle bones) fused to each other and to the tibia, forming a tibiotarsus. The tibia was shorter than the femur, giving the hind limb stocky proportions. Three functional digits were on the foot (the second, third, and fourth), while the first digit, or hallux, did not contact the ground. Although skull proportions varied, abelisaurid skulls were generally very tall and very short in length. In Carnotaurus, for example, the skull was nearly as tall as it was long.