A new Spinosaurus fossil has revealed that this gigantic predatory dinosaur was a proficient swimmer. The first fossil of the creature’s tail has been discovered, revealing large spines that indicate a paddle shape like a crocodile’s tail – the first dinosaur to show any kind of aquatic adaptation.
But the creature has only been known from scattered bones, after the most complete fossil was destroyed in World War II. And even then, very little had been known about the tail. Most reconstructions showed the Spinosaurus with a long, tapered tail – the same kind you’d see on a T-rex or any other therapod.
But excavations in the Moroccan Sahara Desert between 2015 and 2019 uncovered new Spinosaurus bones, including the long-sought tail. It turns out that this tail was made up of tall spines, some as long as 1 m (3.3 ft), as well as elongated chevrons – the bones that protrude out from under the vertebrae.
Much like the sail on the dinosaur’s back, this bone structure would have supported a tall, flat tail. That shape would have made the perfect paddle, propelling the huge creature through water in pursuit of prey. It also had denser vertebrae, which appear to help with ballast.