A verdict on which group of vertebrates it should be placed into, including positive and negative reasons.
Though the platypus’s bizarre construction can often lead to questions as to its classification, it is officially regarded as a mammal.
The platypus has many properties associated with mammals: They have fur covering their bodies; they feed their young through the mammary glands, and are warm blooded. Some features of the platypus, however, suggest a rather different origin.
The most controversial aspect of the platypus is the fact that it lays eggs. Though every other class of vertebrate lays eggs, mammals are normally born live. Other attributes, such as the duck-like snout, the webbed feet and claws initially led scientists to believe that the animal had been faked!
It could be argued that the platypus is an amphibian. They normally live both in and out of water, and must submerge to lay their eggs, much like amphibians. However, amphibians cannot have fur, are cold-blooded, and begin life as tadpoles or larva before developing into their adult form. None of these features applies to a platypus.
Overall, the majority of a platypus’s characteristics point to it being a mammal, with its egg-born status being something of an anomaly. The platypus therefore has a unique classification: A monotreme. The only other animal with this identity is the echidna.