Spinosaurus: the sail-backed, semi-aquatic theropod of North Africa

When and where

Spinosaurus lived during the Cenomanian stage of the Late Cretaceous, between 99 and 93 million years ago, across what is now North Africa. Fossils have come from Egypt, Morocco, Algeria, Tunisia, and Niger. The animal lived in a vast river-and-mangrove system that ran across what is now the Sahara, where lungfish, sawfish, and crocodylomorphs were the most common neighbours, not other large theropods. That ecology matters: it set up the question of what role Spinosaurus played, and recent finds answer that question with "fisher" rather than "land predator."

How we know

German paleontologist Ernst Stromer described Spinosaurus aegyptiacus in 1915 from material recovered in the Bahariya Formation of Egypt. The original Munich specimens were destroyed during an Allied bombing raid on the night of 24-25 April 1944, leaving only Stromer's notes and photographs for decades. New material began appearing in Morocco in the 1990s, and in 2014 a partial skeleton excavated near Erfoud, Morocco was published, providing the first solid evidence of the animal's body proportions in a century. A 2020 paper described an articulated tail with elongated neural spines that flatten into a paddle-like fin, supporting the semi-aquatic interpretation. Source: Wikipedia entry on Spinosaurus.

What set it apart

Three features make Spinosaurus a genuine outlier among theropods. First, the sail. Neural spines on the back vertebrae extended up to 1.65 metres above the body, supporting a sail of skin and connective tissue most likely used for display, although thermal regulation has not been ruled out. Second, the skull. Long and narrow, with conical teeth and pressure-receptor pits in the snout, it matches the skull design of fish-eating crocodylians far more closely than any other theropod skull. Third, the tail and limbs. The dorsoventrally tall paddle tail, short hindlimbs, and dense bone walls all point to a body adapted for propulsion through water rather than running on land. Length came in around 15 metres, weight at 7 to 9 tonnes, making Spinosaurus the longest carnivorous dinosaur ever found.

For collectors and classrooms

A scaled Spinosaurus figurine teaches the post-2014 anatomy: shorter hind legs than older models showed, paddle tail, narrow skull. Browse a hand-painted figurine.