Palaeontology: Spinosaurs did swimmingly well

A group of dinosaurs called spinosaurs were well-suited to life in the water, unlike other non-avian dinosaurs. This suggestion is based on the analysis of a well-preserved fossil tail of Spinosaurus aegyptiacus, published in Nature this week.

Spinosaurs were a successful group of large predatory dinosaurs, with a fossil record that spans over 50 million years. Nizar Ibrahim and colleagues describe an almost complete tail from a subadult Spinosaurus found in the 95-million-year-old Kem Kem beds in south-eastern Morocco. Previously, Spinosaurus was known only from incomplete fossils; the only other associated specimen to be discovered was destroyed during World War II. By contrast, the fossil analysed by Ibrahim and colleagues is the most complete skeleton of a Cretaceous theropod yet found in mainland Africa.

The fossil reveals that Spinosaurus had a flexible tail with a unique shape formed by a series of extremely tall neural spines. Modelling studies suggest that the paddle-like tail would have been flexible and able to move laterally to create thrust, propelling the dinosaur through the water in a manner similar to that of modern crocodiles. The idea that spinosaurs took to the water is not new. Previous studies had suggested that they may have been waders that fished from close to shore. However, this new evidence of specialised tail-propelled locomotion implies the spinosaurs were aquatic animals that may have hunted for prey in the water.