Why was the platypus hard to classify?

Answer 1

The platypus is not difficult to classify: it possesses the defining characteristic of mammals, which is nurturing the young with mothers' milk. It has all other characteristics of mammals, such as breathing through lungs, having fur on its body, and having a four-chambered heart.

The only way it differs from mammals is that it happens to lay eggs. This is not so unusual, given that no other vertebrate group (except for birds) has only one method of reproduction.

Answer 2

Because classifications represent arbitrary divisions that may or may not correspond to reality. In the case of the platypus, the specific difficulty is that while it appears in most respects to fit the classification "mammal" ... it's warm blooded, has hair, and secretes milk... it also lays eggs, which is not a characteristic we normally associate with mammals.

Answer 3

It is not that the platypus does not fit "nicely" into the vertebrate group: the problem is that man's classifications are too limited. The platypus is a mammal and a vertebrate in every sense of the word, but it lays eggs. Together with echidnas, platypuses form the small group of mammals known as monotremes which are distinguished by the fact that they are the only mammals which do not give live birth.

Answer 4

It is not difficult to classify a platypus as a mammal because it has more mammalian characteristics than other characteristics. The essential difference is that the platypus lays soft-shelled, leathery eggs, instead of giving birth to live young.

Platypuses are mammals because, like all mammals, they feed their young on mothers' milk. This is despite their being egg-laying mammals. The defining trait of a mammal is to have mammary glands, to produce milk for its young. The platypus produces its milk from numerous glands over its underside, and the milk runs into grooves from which the young drink. This is unlike other mammals which have teats.

There are other reasons why platypuses are classified as mammals, such as having skin, hair or fur, being warm blooded and breathing via lungs (not gills).

Most mammals are also characterised by the following anatomical features, which the platypus shares:

- A flexible neck with seven cervical vertebrae

- Mammals also show enhanced neocortex development

- Sound is produced by the larynx (a modified region of the trachea)

- limbs are oriented vertically

- The mammalian heart has 4 chambers

- Internal temperature is generally high

- Egg development occurs in the uterus (excluding monotremata)

- They have sweat glands

- A single jaw bone

- Diaphragm

- Three bones for a middle ear

- Give birth to young alive

- Feeds milk to its young

- Has hair on its body

Answer 5

The platypus is a mammal (like humans) but they reproducing by laying eggs. They are one of only two mammals that do this--thus they are hard to categorize.

Answer 6

Because it was one of two mammals that lays eggs, and feeds its young milk.