Dinosaurs are one of the most successful groups of animals to have ever lived. From meager beginnings they would start out small, but would ultimately culminate into many diverse varieties, grow to enormous sizes, fulfill several ecological niches, and populate every continent on the planet. The first dinosaur to be scientifically described was the Megalosaurus in 1824, discovered by geologist William Buckland. In 1842, anatomist and paleontologist Sir Richard Owen would coin the term "Dinosaur" to describe these fossilized and seemingly related gigantic animals. The word "Dinosaur" means "Fearfully Great Lizard" (or "Terrible Lizard" by modern definition). Dinosaurs are broken down into two major groups: the saurischians (dinosaurs whose hips are anatomically lizard-like in appearance, including theropods and sauropods), and the ornithischians (dinosaurs whose hips are anatomically bird-like in appearance, which includes the majority of herbivorous dinosaurs). The first dinosaurs would evolve in the Late Triassic period (over 230 million years ago), and all non-avian dinosaurs would become extinct at the end of the Late Cretaceous period, 66 million years ago. Only one branch of the dinosaur family tree would survive the extinction, and are still with us today. The survivors are called the avian-dinosaurs, but they are more commonly known as birds.