Pterosaur fossils are very rare, due to their light bone construction. Complete skeletons can generally only be found in geological layers with exceptional preservation conditions, the so-called "Lagerstätten". The pieces from one such "Lagerstätte", the Late Jurassic Solnhofen Limestone in Bavaria, became much sought after by rich collectors. In 1784, the Italian naturalist Cosimo Alessandro Collini was the first scientist in history to describe a pterosaur fossil. At that time the concepts of evolution and extinction were only imperfectly developed. The bizarre build of the pterosaur was therefore shocking, as it could not clearly be assigned to any existing animal group. The discovery of pterosaurs would thus play an important role in the progress of modern paleontology and geology. If such creatures were still alive, only the sea was a credible habitat and Collini suggested it might be a swimming animal that used its long front limbs as paddles. A few scientists continued to support the aquatic interpretation even until 1830, when the German zoologist Johann Georg Wagler suggested that "Pterodactylus" used its wings as flippers and was affiliated with Ichthyosauria and Plesiosauria.