Many early palaeontologists saw nothing wrong with adding a missing bone or two. Both the American Museum of Natural History and the Carnegie Museum in Pittsburgh acquired fossil skeletons of Apatosaurus with skulls from different dinosaurs in the 1880s. But the prices that well-preserved Chinese bird fossils fetch have made faking extremely profitable. The problems start with the Chinese peasants who dig up most of the bird fossils. Fossils often split along the plane of the bones, giving them two sides of a single animal, known as a part and counterpart.
Some composites are even good enough to fool the professionals.
Luis Chiappe of the Natural History Museum of Los Angeles County recalls one specimen that aroused his suspicions. But careful measurement showed that one leg was longer than the other. And only when he examined it closely did he find the mortar that had glued two slabs together. These reveal joints or voids within the rock. Derstler says shrimp and fish are often painted to enhance their appearance.