Spinosaurus

Spinosaurus (; ) is a genus of large spinosaurid theropod dinosaurs that lived in what is now North Africa during the Cenomanian stage of the Late Cretaceous period, about 100 to 94 million years ago. The genus was known first from Egyptian remains discovered in 1912 and described by German palaeontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material came to light in the early 21st century. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The type species, S. aegyptiacus, is mainly known from the Bahariya Formation in Egypt and the Kem Kem beds in Morocco. The other species, S. mirabilis, is known from the Farak Formation in Niger. Although another potential species, S. maroccanus, has been recovered from the Kem Kem beds, this dubious species is likely a junior synonym of S. aegyptiacus. Other possible junior synonyms include Sigilmassasaurus from the Kem Kem beds and Oxalaia from the Alcântara Formation in Brazil, though other researchers propose both genera to be distinct taxa.

Spinosaurus is among the largest known terrestrial carnivores; other large carnivores comparable to Spinosaurus include theropods such as Tyrannosaurus, Giganotosaurus and the contemporary Carcharodontosaurus. A 2022 study suggests that S. aegyptiacus could have reached in length and in body mass. The skull of Spinosaurus was long, low, and narrow, similar to that of a modern crocodilian, and bore straight conical teeth with few to no serrations. It would have had large, robust forelimbs bearing three-fingered hands, with an enlarged claw on the first digit. The distinctive neural spines of Spinosaurus, which were long extensions of the vertebrae, grew to at least long and were likely to have had skin connecting them, forming a sail-like structure. The hip bones of Spinosaurus were reduced, and the legs were very short in proportion to the body. Its long and narrow tail was deepened by tall, thin neural spines and elongated chevrons, forming a paddle-like structure.