The first recognized bones of dinosaurs were so large that naturalists named these animals “terrible lizards”. As they tried to reconstruct these fossils, the naturalists had referred to animals that they already knew about. Hence the result of their efforts was the idea that dinosaurs were large cumbersome beasts, which resembled lizards.
Other early ideas that naturalists had about dinosaurs were that they lolled about, and conducted belching contests. And if dinosaurs had to stand up, they leaned on nearby trees. Although there were no tailprints found with footprints in the fossil record, dinosaurs were depicted with their tails dragging on the ground. This particular concept continued well into the 20th Century.
Various early ideas of how dinosaurs looked are on display at the Dinosaur Court of the Crystal Palace in London. Opened in 1854, the Court featured dinosaurs that looked like lizards or stood like mammals. However by 1900, these depictions of dinosaurs were considered to be out of date.
The first dinosaur ever named, Megalosaurus was actually a theropod. However, this animal was depicted in the Dinosaur Court as a gigantic four-footed monitor lizard. Meanwhile, other early depictions gave these theropods elephant-like qualities as well as lizard ones.
Theropods, in general, were thought of as large mammals standing on sturdy legs, dragging their tails. After two discoveries in 1858 and 1859, the view of theropods changed. First the Hadrosaurus (an ornithopod dinosaur) was discovered in New Jersey. This dinosaur walked upright. Meanwhile one of the tiniest dinosaurs, the Compsognathus, was found in Germany. Now evidence pointed to the fact that theropods could be any size and also walk upright. However the notions that they were quick predators remained years off.
Meanwhile because of their large size, sauropods were believed to live in water or at the very least in swamps and marshes. This idea came from the large whales of the oceans. For example, Brachiosaurus was thought to stick its head out of water, while remaining submerged. However, this massive dinosaur would have suffocated from the water pressure. In addition, when the sauropods did walk on land, they were depicted as alligators with drooping stomachs and dragging tails. The idea that these massive animals could use their tails as weapons had not occurred to naturalists at that time.