There is no other creature quite like the platypus (Ornithorhynchus anatinus). Its bizarre appearance once led people seeing it for the first time to believe a duck's bill had been sewn on to a mammal's body. With its streamlined body, flat, beaver-like tail and short legs it is hardly surprising it was thought to be a practical joke. The peculiarity does not end with its looks: the flexible bill is covered in sensory receptors and the platypus is one of only five mammal species to lay eggs. The female has no nipples to suckle the young so secretes milk for them to lap up.
The male also has his claim to fame: he is the only mammal to have poisonous spurs. A sharp, hollow spur 15mm long on the inside of each hind leg can deliver enough toxin to kill a dog and inflict considerable pain on a human.