Mammals

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types of mammals

Types of Mammals: According to biological studies, mammals started to appear during the dinosaur era (200+ million years ago). Initially, mammals were small in size, and after the extinction of dinosaurs (end of the Mesozoic era – 66 million years ago), their sizes had started to evolve into more prominent forms.

By nature, mammals are warm-blooded animals covered with furry hairs which make them live anywhere in the world from icy polar regions to tropical forests.

There are many biological classifications and various debates on types of mammals amongst the biologists themselves. The mammals are classified under kingdom – Animalia, phylum – Chordata, and class – Mammalia.

However, the commonly accepted types of mammals are grouped into three major categories based on how mammals reproduce their babies:

Types of Mammals

1. Monotremes Mammals

Monotremes Mammal (Platypus)

This type of mammals lay eggs, and the offsprings come out from the hatched eggs. These are the ancient form of mammals, and even today, these mammals do exist. The babies feed on mother’s milk similar to any other mammals. Monotremes mammals belong to the Sub-class Prototheria.

(Example: Platypus from Australia). Check out a post on Platypus featuring on animals with best sensors.

2. Marsupial Mammals

Marsupials Mammal (Kangaroo)

This type of mammal gives birth to the barely formed offspring, and the baby grows on a pouch on the mother’s belly. From there, babies drink mother’s milk to get all nutrients and become a fully evolved baby. Marsupial mammals belong to the Sub-class Metatheria.

(Example: Kangaroo from Australia).

3. Placental Mammals

Placental Mammal (Giraffe)

This type of mammal constitutes a more significant chunk of mammals in the animal kingdom. The offsprings grow into a well-formed structure inside the mother’s belly for a long time (time differs between size and shape of mammals) before the mother gives birth to them when ready. The baby in the womb gets the nourishment from the mother’s diet via the umbilical cord (attached to the mother) inside the placenta (an organ where the baby grows). The placental mammals belong to the sub-class Eutheria.

(Examples: Humans, Giraffes, monkeys & more).

Characteristics of Mammals

Although the mammals can be monotremes, marsupials or placentals, they all share a list of key features:

  • warm-blooded

    1. Warm-blooded

    Mammals maintain a constant body temperature (via homeostasis) which are slightly higher than the environment temperature where they live in. They are usually known as homeothermic species (note: birds are also homeothermic).

  • Vertebrates

    2. Vertebrates

    All mammals have a spinal cord (hollow tube) which is connected via vertebrae. All mammals are built along the same chordate body plan. However, it extends to the length of the animal as designed. All mammals have three middle ear bones which are a unique feature.

  • Nourish on Milk

    3. Nourish Young on Milk

    The mother in mammals produce milk via mammary glands (i.e., exocrine glands) to nourish the offsprings with nutrients until their digestive system improves to take solid food (plant material in case of herbivores or meat in case of carnivores).

  • Body Fur

    4. Body covered with hair

    Most mammals get their body heat from the food they eat. The body heat allows mammals to live in any climatic conditions. The hair/fur (composed of Keratin) on mammals provide excellent insulation to keep heat inside the body and saves energy for them. They are various kinds of animal coats namely:

    • Blubber: A think layer which insulates the fat. This type of skin is shared among the marine mammals. (Example: Dolphins)
    • Fur: Certain animals have two layers of fur namely outer guard hair (coat/fur) and the inner woolly underfur. The outer fur sheds the water and keeps the underfur dry. (Example: Tiger)
    • Spines: The outer hair for some animals are made into stiffer, sharper and thicker spines which protect from the predators. (Example: Porcupine)
    • Scales: The skin for certain mammals are formed by fusing overlapping scales of modified hairs. Thus, the skin resembles a thick outer shell which provides excellent protection from predators. (Example: Pangolin)
  • Give Birth

    5. Give Birth From Womb

    Except for monotremes, all mammals give birth to offspring. The young ones grow in the female’s womb until it is fully developed and delivered out.

Within the Mammalia class, there are about 5500+ known species of mammals identified and classified under 30 different biological orders. Still, a new set of mammal species are being discovered every year and added to this list.

Monotremes Mammal Orders

  • Order Monotremata (Monotremes)

Marsupial Mammal Orders

  • Order Dasyuromorphia (Marsupials)
  • Order Didelphimorphia (Marsupials)
  • Order Diprotodontia (Marsupials)
  • Order Microbiotheria (Marsupials)
  • Order Notoryctemorphia (Marsupials)
  • Order Paucituberculata (Marsupials)
  • Order Peramelemorphia (Marsupials)

Placental Mammal Orders

  • Order Afrosoricida (Placental)
  • Order Artiodactyla (Placental)
  • Order Carnivora (Placental)
  • Order Cetacea (Placental)
  • Order Chiroptera (Placental)
  • Order Cingulata (Placental)
  • Order Dermoptera (Placental)
  • Order Erinaceomorpha (Placental)
  • Order Hyracoidea (Placental)
  • Order Lagomorpha (Placental)
  • Order Macroscelidea (Placental)
  • Order Perissodactyla (Placental)
  • Order Pholidota (Placental)
  • Order Pilosa (Placental)
  • Order Primates (Placental)
  • Order Proboscidea (Placental)
  • Order Rodentia (Placental)
  • Order Scandentia (Placental)
  • Order Sirenia (Placental)
  • Order Soricomorpha (Placental)
  • Order Tubulidentata (Placental)
  • Order Condylarthra – extinct (Placental)
  • Order Creodonta – extinct (Placental)
  • Order Desmostylia – extinct (Placental)
  • Order Embrithopoda – extinct (Placental)

Cite this article as: "Mammals," in Bio Explorer by Jack Kirsten, January 7, 2018, https://www.bioexplorer.net/animals/mammals/.

References

  • [1] – “Tree of Life Web Project”. Accessed August 26, 2018. Link.
  • [2] – “Mammal Species of the World – Browse”. Accessed August 26, 2018. Link.
Mammals
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