Spinosaurus is called "spiny lizard" because it had a series of large neural spines up to 6 feet (1.8 m) long coming out of its back vertebrae, probably forming a sail-like fin that may have helped in thermoregulation, mating rituals and/or intraspecies rivalry. Spinosaurus had a relatively flexible upper spine (these vertebrae had modified ball-and-socket-joints) so it could arch its back somewhat, perhaps being able to spread the sail (like opening the ribs of a fan).Spinosaurus was bipedal (it walked on two legs). It was about 40-50 feet long (12-15 m) and weighed 4 tons or more (some paleontologists estimate it weighed up to perhaps 8 tons); it is the largest known spinosaurid (a type of large, meat-eating dinosaur). It had a large head with sharp, straight, non-serrated teeth in powerful, crocodile-like jaws. Its arms were smaller than its legs but were larger than the arms of most other theropods. It may have gone on all fours at times.Spinosaurus lived during the middle Cretaceous period, about 95 million years ago in the tropics near sea level. At the same time and place, there was another sail-backed dinosaur, Ouranosaurus, a large, bipedal plant-eater.Spinosaurus' huge sail may have been used for regulating its temperature. It could collect warmth from the sun and also disperse excess body heat when in the shade. The presence of this sail as a thermo-regulatory device is evidence that Spinosaurus may have been a cold-blooded animal. The sail may also have been used for mating rituals, attracting mates. The sail may have been brightly colored, like the fins of some modern-day reptiles.
Spinosaurus was a carnivore, a meat eater with huge teeth and powerful jaws. It ate dinosaurs and large fish. The teeth were long and sharp but had little or no serrations. It was a large, fierce predator that could perhaps even kill large sauropods. Spinosaurus may also have been a scavenger.Spinosaurus was an advanced theropod, whose intelligence (as measured by its relative brain to body weight, or EQ) was high among the dinosaurs.Spinosaurus walked on two muscular legs and was a relatively fast, two-legged runner. It may have gone on all fours at times, given its relatively long arms. Dinosaur speeds are estimated using their morphology (characteristics like leg length and estimated body mass) and fossilized trackways.Spinosaurus was named in 1915 by paleontologist Ernst Stromer von Reichenbach, from an African fossil. Fossils have been found in Egypt and Morocco, in Africa.