Also known as the duck-billed platypus, the platypus is one of the most specialized and unique mammal species on planet Earth. Not only is it one of only five species of mammals that lays eggs, but the males are also venomous, which is also an incredibly rare trait in mammals! History: Although there is some disagreement over the worldwide population of platypuses, the general consensus is that while they are not in any immediate danger of becoming endangered or going extinct, they are considered near threatened on the IUCN red list. There are many potential hazards for platypus numbers, including habitat disruption from dams, irrigation systems, and pollution. Scientific Name: Ornithorhynchus anatinus Characteristics: Because of its unique characteristic, including its duck bill, beaver-like tail, and otter-like feet, the platypus is often the focus of study for individuals interested in evolutionary biology. Size: 4.75 inches long and 1.5 inches tall.