Spinosaurus aegyptacus, as its name implies, was first discovered in Egypt and lived in North Africa during the mid-Cretaceous. This sail-backed predator is the largest-known theropod, at 40-60 feet in length, though estimates of its weight vary wildly from 7-23 tons. To give a better idea of scale, the sail on its back is roughly 5 and a half feet tall.
A member of the Megalosauria, Spinosaurus had a highly-modified skull convergent with modern crocodylians, suggesting it may primarily have eaten fish, although with its large size and strong jaws it may certainly have been more opportunistic than that and probably could have eaten anything it could catch. The sail on its back, meanwhile, may have been similar in purpose to the plates on the back of the Stegosaurus from the other day - it may have been used in thermoregulation, or in sexual display - or, as some have suggested, the spines may not have supported a sail but instead a camel-like hump, where fat was stored. We do know for certain that Spinosaurus was at least semiaquatic, though, based on isotope analyses of fossilized teeth, and a hump may have impeded swimming while a sail likely would not have.