 Rather than being a unique outlier, the platypus is the last demonstration of what was once a common mammalian characteristic, and it can be used as a model for non-therian mammals and their venom delivery and properties.The venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands located in the upper thigh connected by a thin-walled duct to a calcaneus spur, or calcar, on each hind limb.Female platypuses, in common with echidnas, have rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands.