Birds are also warm-blooded but lay eggs, and reptiles are cold-blooded egg-layers that rely on the Sun or another heat source to warm them up. To simply separate the orders, mammals are warm-blooded, give birth to live young and feed them milk. When it was discovered, the platypus was difficult to classify, bearing characteristics of mammals, reptiles and birds. This hybrid name was accepted in accordance with the rules of priority when classifying animals with scientific names.
The animal later became recognised as Ornithorhynchus anatinus, meaning bird-snouted flat-foot. So in 1803 Johann Friedrich Blumenbach published another description of the animal under the name Ornithorhynchus paradoxus - 'paradoxical bird-snout'. However, Platypus was already in use as the name of a genus of wood-boring ambrosia beetles. In 1799 he was the first to scientifically describe it, assigning it the species name Platypus anatinus, meaning flat-footed duck. George Shaw, keeper of the natural history collections at the British Museum (which were to later become the Natural History Museum), accepted the platypus as a real animal. But the platypus, as it was soon realised, was not among these. The nineteenth century saw a number of hoax animals on display, such as P T Barnum's Fiji (Feejee) Mermaid and Albert Koch's Missouri Leviathan.