Spinosaurus (; lit. 'spine lizard') is a genus of large spinosaurid theropod dinosaurs that lived in what is now North Africa during the Cenomanian age 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. Possible junior synonyms include Sigilmassasaurus and the dubious S. maroccanus from the Kem Kem beds and Oxalaia from the Alcântara Formation in Brazil, though the distinction and validity of these taxa have been debated. 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 14 m (46 ft) in length and 7.4 t (8.2 short tons) 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 1.65 m (5.4 ft) 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. Spinosaurus is known to have eaten both aquatic and terrestrial prey. Evidence suggests that it was semiaquatic, although the extent of its swimming capability has been strongly contested. Spinosaurus's leg bones had a high bone density, allowing for better buoyancy control. Multiple functions have been put forward for the dorsal sail, including thermoregulation and display; either to intimidate rivals or attract mates. It lived in a humid environment of tidal flats and mangrove forests alongside many other dinosaurs as well as fish, crocodylomorphs, squamates, turtles, pterosaurs, and plesiosaurs.
Discovery and naming
Initial finds
The first discovery of Spinosaurus may have been in October 1898, when French geologist Fernand Foureau unearthed two unusual teeth in Cenomanian-aged sediments of the Djoua Escarpment in what is now southern Algeria, then French Algeria. Foreau found the specimens while on the Foureau-Lamy Expedition of 1898-1900, which traveled across the Sahara from Algeria to Lake Chad. In 1905, French geologist Emile Haug described the fossils unearthed while on the expedition, including the two teeth which he assigned to the fish Saurocephalus. However, in 1915 German paleontologist and describer of Spinosaurus Ernst Stromer reassigned the teeth to Spinosaurus. Later studies have agreed with this assessment, however the teeth themselves has since been lost. The first confidently referable remains of Spinosaurus were discovered in the autumn of 1912 by Austro-Hungarian paleontologist Richard Markgraf, a fossil collector who was financed by Stromer and the Bavarian Academy of Sciences, in deposits of the Bahariya Formation in the Bahariya Oasis of western Egypt. The sediments of the Bahariya Formation come from the Cenomanian stage of the Late Cretaceous period, one of many Cretaceous-aged formations of North Africa. In 1915, Stromer described these remains as belonging to a new genus and species of dinosaur, Spinosaurus aegyptiacus. The generic name Spinosaurus comes from the Latin spina, meaning "spine", and the Greek sauros, meaning "lizard", and thus "spine lizard". The specific name aegyptiacus derives from Egypt, where the fossils were unearthed. Spinosaurus aegyptiacus' type specimen (BSP 1912 VIII 19) consists of elements of the mandible (lower jaw), a maxilla (upper jaw) fragment, cervical (neck), caudal (tail), and dorsal (back) vertebrae, including much of the neural spines, ribs, teeth, and some gastralia (belly ribs). In April 1914, another expedition to the Bahariya Oasis by Markgraf unearthed an incomplete skeleton (BSP 1922 X45) of a spinosaurid. This skeleton was poorly preserved and, as a result of illegal unpacking and insufficient repacking by Anglo-Egyptians during World War I, was greatly damaged. After much deliberation due to the war and poor Anglo-German relations, the skeleton arrived in Germany in 1922 where it was described by Stromer in 1934. Stromer assigned the skeleton to Spinosaurus, but considered it different enough from S. aegyptiacus that it would belong to its own Spinosaurus species, "Spinosaurus B".
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