When the first dinosaur skeletons were hewn out of gravel quarries in England during the 1820s and ’30s, the gentlemannaturalist immediately recognized their strange combination of characteristics. (real dinosaur suit)These great fossils combined traits found in lizards, in birds, in mammals, and in crocodiles as well. Owen was especially impressed by the advanced, birdlike shape of dinosaurs’ hip bones, and he used their characteristics to set dinosaurs apart from all other animals with backbones. And so can we. A very good anatomical definition for the Dinosauria is “a vertebrate group close to crocodiles but with at least some important birdlike features in the hind leg.”
Sir Richard Owen’s astute observations are too often ignored. (realistic dinosaur suit)Twentieth-century paleontologists have fallen into the bad habit of reconstructing the dinosaurs’ life functions by using crocodiles as a living model. But the earliest researchers of the nineteenth century proved beyond a doubt that the dinosaurs’ powerful hind legs must have operated like the limbs of gigantic birds. (real dinosaur model)And further birdlike characteristics turned up in the dinosaurs’ backbone. Many species of dinosaur had hollow chambers in their vertebrae. In life, these bony caverns were filled with air sacs connecting to the lung, just as in many birds today. Later nineteenth-century discoveries made the dinosaur-bird connection very intimate. Archaeopteryx, the oldest fossil bird, was discovered in 1861 and made headlines because it looked so much like a small dinosaur with feathers. (animatronic dinosaur) The great Darwinian orator and advocate Thomas Henry Huxley pounded the pulpit of evolutionary theory by pointing to Archaeopteryx as the missing link between dinosaurs and modern birds.
It’s important to be clear about the reverse definition as well: what dinosaurs are not. Dinosaurs are not lizards, and vice versa. Lizards are scaly reptiles of an ancient bloodline. The oldest lizards antedate the earliest dinosaurs by a full thirty million years.