Dinosaurs are a type of reptile, and they evolved from another group of reptiles called ‘dinosauromorphs’ around 250 million years ago. The dinosauromorphs were small and humble animals, and they didn’t look anything like T. rex or Brontosaurus.
Instead, they were the size of house cats, walked on all fours, and had long, skinny limbs like a greyhound. The dinosauromorphs weren’t at the top of the food chain, but their speed and agility ensured their success.
Steve is a professor and palaeontologist at the University of Edinburgh and the author of the book The Rise And Reign Of The Mammals (£20, Picador), a 325-million-year odyssey of mammalian evolution and the people who study mammal fossils.