Spinosaurus witnessing a lunar impact. Computer artwork of a Spinosaurus dinosaur standing under a flash of light in the sky caused by a massive asteroid colliding with the Moon. Spinosaurus were enormous meat-eating dinosaurs that lived during the late Cretaceous period (99 to 65 million years ago). Their typical length from tail tip to snout was 12-15 metres, and they are believed to have weighed at least 8 tonnes or more.