The word dinosaur was coined by Richard Owen in 1841, deinos (terrible) + sauros (lizard) which describe various extinct reptiles of the orders Saurischia and Ornithischia that flourished during the Mesozoic Era. Dinosaurs were carnivorous or herbivorous, dwelled mostly on land, and varied from the size of a small dog to the largest land animals that ever lived. Archaeopteryx ("original bird" or "first bird"), is a genus of theropod dinosaur that is closely related to birds. Archaeopteryx was roughly the size of a raven with broad wings that were rounded at the ends and a long tail compared to its body length. Since the late 19th century, it has been generally accepted by paleontologists, and celebrated in lay reference works, as being the oldest known bird, though some more recent studies have cast doubt on this assessment, finding that it is instead a non-avialan dinosaur closely related to the origin of birds.