Spinosaurus

Spinosaurus, genus of theropod dinosaurs belonging to the family Spinosauridae, known from incomplete North African and West African fossils that date to Cenomanian times (roughly 100 to 94 million years ago). Spinosaurus, or “spined reptile,” was named for its “sail back” feature, created by tall vertebral spines. The genus is made up of two species, S. aegypticus and S. mirabailis.

Discoveries

It was named by German paleontologist Ernst Stromer in 1915 on the basis of the discovery of a partial skeleton from Bahariya Oasis in western Egypt by his assistant Richard Markgraf. These fossils were destroyed in April 1944 when British aircraft inadvertently bombed the museum in Munich in which they were housed. For several decades Spinosaurus was known only from Stromer’s monographic descriptions; however, additional fragmentary remains were discovered during the 1990s and 2000s in Algeria, Morocco, Tunisia, and the 2020s in Niger. Related taxa in the family Spinosauridae include Baryonyx from England, Irritator from Brazil, and Suchomimus from Niger.

Natural history

Spinosaurus, which was longer and heavier than Tyrannosaurus, is likely the largest known carnivorous dinosaur. It possessed a skull 1.75 metres (roughly 6 feet) long and a body length of 14–18 metres (46–59 feet). The dinosaur’s mass remains a subject of much debate, with some early studies estimating that the largest forms could have weighed up to 20,000 kg (22 tons). Later studies, however, reported that the mass of largest members of the genus was rarely more than 7,400 kg (8.1 tons).

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Like other spinosaurids, Spinosaurus possessed a long narrow skull resembling that of a crocodile and nostrils near the eyes, instead of near the end of the snout. Its teeth were straight and conical, instead of curved and bladelike as in other theropods, and it had a broad, paddle-shaped tail All these features are adaptations for swimming and piscivory (that is, the consumption of fish).

The lifestyle of this dinosaur remains a a subject of active debate. Early studies posited that the bones of its skeleton were more compact and denser than those of similar land-dwelling theropods, which allowed it greater control over its buoyancy underwater; this characteristic led some researchers to argue that Spinosaurus was primarily an aquatic predator rather than a terrestrial one. However, subsequent modeling studies and fossil evidence suggested that although Spinosaurus could swim, it did not have dense bones, which limited its ability to swim suggesting, in turn, that it was a bipedal terrestrial predator. Additional fossil evidence uncovered in Niger in 2020 revealed the existence of a large, flattened tail that covered loosely connected bones that allowed Spinosaurus to propel itself in the water. However, modeled reconstructions of Spinosaurus with the tail suggested that it was too buoyant to dive and pursue fish underwater, leading researchers to classify Spinosaurus as a semi-aquatic, wading predator.

Other spinosaurids have been found with partially digested fish scales and the bones of other dinosaurs in their stomach regions, and spinosaurid teeth have been found embedded in pterosaur bones. The sail over the animal’s back was probably used for social displays or species recognition rather than for temperature regulation. Some authorities maintain that the sail was actually a hump used to store water and lipids.