Mammals can be found in various shapes and sizes. Although it is hard to
believe, monkeys and whales are relatives as mammals that have the main
characteristics that distinguish them from other animal groups.
Not only whales, there are several other mammals that also live in the sea.
Some of them may still be considered fish, not a group of mammals.
What is a mammal?
Reporting from AZ Animals, in the subphylum vertebrates (backbones), there
is a class of mammals. Mammals are divided into three groups, namely
monotremes, marsupials, and eutherians or placental mammals.
This grouping is based on several characteristics, especially the
reproductive system of animals. Monotremes are egg-laying mammals. Examples
are the platypus, echidnas, and their ancestors.
Marsupials or marsupials are mammals that give birth to young living in
pouches. Examples of common marsupials are kangaroos, opossums and Tasmanian
devils.
While eutherians are mammals that give birth to a relatively late stage of
development and feed their young during pregnancy with the placenta.
Marine mammals As the name implies, marine mammals are mammals that spend
most of their time in the sea.
Marine mammals have unique adaptability to cope with cold temperatures, high
pressure depths, and so on. Some examples of marine mammals are dolphins,
seals, and walruses.
Many marine mammals have fins, instead of arms and legs like other mammals.
Interestingly, the fin anatomy of marine mammals is very similar to the arms
or legs of land mammals. For example, dolphin pectoral fins have a humerus,
radius, and ulna like the arms of land mammals.
Marine mammals also have three main characteristics in common, namely hair
or feathers, middle ear bones, and mammary glands. Are whales a mammal? Yes,
whales are marine mammals, so the blue whale is the largest mammal that has
ever lived on Earth.
There are many species of whales and all of them have the characteristics of
a mammal. Whales are eutherian or placental mammals that give birth to live
offspring. Whales have mammary glands, lactate, and suckle their young.
All whale species also have hair follicles, although most do not grow as in
other mammals.
Whales have three middle ear bones typical of mammals. In addition, whales
can breathe air, however, they can stay underwater for a long time before
re-emerging to the surface.
