Spinosaurus, meaning “Spine lizard,” is a genus of theropod dinosaur from the lower Albian to lower Cenomanian stages of the Mid Cretaceous Period (112 to 97 million years ago). It lived in what is now North Africa. The type species is S. aegyptiacus. A potential second species, S. maroccanus, was discovered in Morocco.

It was the first known dinosaur fossil from Egyptian remains discovered in 1912 and described by German paleontologist Ernst Stromer in 1915. The original remains were destroyed during World War II, but additional material has been found in recent years. Richard Markgraf is credited with the discovery of S. aegyptiacus, which consisted of a partial skeleton found in the Bahariva Formation of western Egypt.

S. maroccanus was originally described by Dale Russell in 1996 as a new species based on the length of its neck vertebrae. Some authors have debated this description, noting that the length of the vertebrae can vary from individual to individual, and since the holotype was destroyed, it remains impossible to prove distinction in both specimens.

Spinosaurus may be the largest of all known carnivorous dinosaurs, even larger than Tyrannosaurus and Giganotosaurus. Estimates published in 2005 and 2007 suggest that it was 41 to 59 feet in length and weighed up to 23 tons. The skull was long and narrow like that of a modern crocodile. The distinctive spines of Spinosaurus, which were long extensions of its vertebrae, grew to at least 5.4 feet long and were likely to have skin connecting them, forming a sail-like structure. Some authors, however, suggested the spines were covered in fat and formed a hump.

Since its discovery, Spinosaurus has been a contender for the longest and largest theropod known. However, that distinction has been a popular debate for nearly a century. It has been listed as among the most massive theropod by Friedrich von Huene in 1926 and Donald F Glut in 1982. In 1988, Gregory Paul listed it as the longest theropod, but gave it a lower mass estimate — only 4.4 tons.

Some authors have estimated Spinosaurus to be slightly smaller than popular estimates based on the size of its skull. A skull size of 4.9 to 5.7 feet would place the dinosaur at an estimated length of 41 to 47 feet, rather than the upper limit of 59 feet. The skull measurements would also give Spinosaurus an estimated weight of 13 to 23 tons. The lower estimate implies that the animal may have been shorter and lighter than its close relatives.

To be sure of the actual size of Spinosaurus, most scientists agree that more complete fossil specimens need to be discovered.

The tall neural spines growing on the animal’s back vertebrae formed the basis of what is usually called the animal’s sail. The length of the neural spines reached over ten times the diameters of the vertebral bodies from which they extended. The neural spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the pelycosaur finbacks Edaphosaurus and Dimetrodon, contrasting also with the thicker spines in the contemporary iguanodont Ouranosaurus.

The sails of Spinosaurus were unusual, although other dinosaurs that lived in the same general region a few million years earlier may have had similar spinal sails. The sail is possibly analogous to that of the Permian synapsid (mammal-like) Dimetrodon, which lived before dinosaurs even appeared.

The sail structure may have also been more hump-like than sail-like. Jack Bowman Bailey in 1997 argued that in Spinosaurus, Ouranosaurus, and other dinosaurs with long neural spines, the spines were relatively shorter and thicker than the spines of pelycosaurs; instead, the dinosaurs’ neural spines were similar to the neural spines of extinct hump-backed mammals such as Megacerops and Bison latifrons.

The skull had a narrow snout filled with straight conical teeth that lacked serrations. There were six or seven teeth on each side of the front of the jaw, and another twelve in both maxilla behind them. The second and third teeth on each side were noticeably larger than the rest of the teeth in the premaxilla (front jaw). The tip of the snout was expanded to hold the larger teeth. A small crest was present in front of the eyes.

Spinosaurus was prominently portrayed in the 2001 film Jurassic Park III. The film’s consulting paleontologist John Horner was quoted as saying: “If we base the ferocious factor on the length of the animal, there was nothing that ever lived on this planet that could match this creature [Spinosaurus]. Also my hypothesis is that T-rex was actually a scavenger rather than a killer. Spinosaurus was really the predatory animal.”

Spinosaurus was portrayed as larger and more powerful than Tyrannosaurus in the film. In one scene depicting a battle between the two dinosaurs, Spinosaurus emerges victorious by snapping the Tyrannosaurus’s neck.

In addition to the Jurassic Park III film, Spinosaurus has been depicted in video games, action figures, books, postage stamps, as well as other movies. Spinosaurus also appeared in documentaries such as Bizarre Dinosaurs, Monsters Resurrected, and Planet Dinosaur.