Characteristics of Mammals - Definition, Types + 70 Examples

2024 Author: Carl Johnson | [email protected]. Last modified: 2023-12-16 06:19

The mammals are the most extensively studied group of animals, making them the best-known vertebrates. This is because it is the group that includes the human being, so after centuries trying to know itself, our species has investigated the rest of the mammals.

In this article on our site we will learn the definition of mammals, which is much more extensive than what we commonly know. Also, we will learn the characteristics of mammals and we will see some known examples and others not so common.

What are mammals?

Mammals are a large group of vertebrate animals with constant temperature, classified in the class Mammalia. Mammals are generally defined as those animals with hair and mammary glands that give birth to their young. However, mammals are much more complex organisms with more defining characteristics than those mentioned.

All mammals stem from a single common ancestor that appeared in the late Triassic, around 200 million years ago. Specifically, mammals descend from the primitive synapsids, amniotic tetrapods, that is, four-legged animals whose embryos develop protected by four shells. After the extinction of the dinosaurs, about 65 million years ago, from this common ancestor, mammals diversified into multiple species, adapting to all environments, terrestrial, aquatic and aerial.

Characteristics of mammals - What are mammals?

What are the characteristics of mammals?

As we said, these animals are not defined by just one or two characters, in fact, they present unique morphological characteristics, in addition to a great ethological complexity that makes each individual unique.

The characteristics of vertebrate mammals are:

Jaw formed only by the dental bone.
The articulation of the mandible with the skull is made directly between the dentary and squamosal bones.
They have three bones in the middle ear (hammer, anvil and stirrup), except for monotremes, which have a reptilian ear, simpler.
The fundamental epidermal structure is hair. All species develop hair to a greater or lesser extent. Some species, such as cetaceans, only have hair at birth, which sheds as it grows. Sometimes this hair is modified, forming, for example, the baleen of whales or the scales of pangolins.
Embedded in your skin are a multitude of sweat and sebaceous glands. Some of them transformed into scent or poisonous glands.
They have mammary glands, which derive from sebaceous glands and secrete milk, which is the necessary food for the young of mammals.
Depending on the species, they have nails, claws or hooves, all of them made of a substance called keratin.
Some mammals have horns These can be very different from each other. Sometimes they have a bony base covered by skin, others also have a chitinous protection and others do not have a bony base, instead it is formed by an accumulation of layers of skin, as is the case with rhinoceros horns.
The mammalian digestive system is highly developed and more complex than in other species. The characteristic that most differentiates them is the presence of a blind sac or appendix.
Mammals have a cerebral neocortex or, in other words, a highly developed brain, which leads them to develop a multitude of capacities complex cognitive.
All mammals breathe air, even if they are aquatic mammals. To do this, the respiratory system of mammals has two lungs which, depending on the species, may or may not be lobed. They also have a trachea, bronchi, bronchioles and alveoli, prepared for gas exchange. They also have a voice organ with vocal cords located in the larynx. This allows you to play multiple sounds.

Characteristics of mammals - What are the characteristics of mammals?

Types of mammals

The classic mammalian definition would exclude some of the earliest mammalian species to appear on the planet. The class Mammalia is divided into three orders: the monotremes, marsupials, and placentals.

Monotremes: The order of monotreme mammals consists of only five species of animals: platypuses and echidnas. These mammals are characterized by being oviparous animals, that is, they lay eggs. In addition, they retain a characteristic of their reptilian ancestors, the cloaca, where the digestive, urinary and reproductive systems converge.
Marsupials: marsupial mammals are characterized by, despite being viviparous animals, they have a very short placental development, completing it in the outside the maternal uterus but inside a bag of skin called a marsupium, inside which are the mammary glands.
Placentaries: Finally, there are the placental mammals. These animals, also viviparous, complete the fetal development inside the maternal womb, when leaving it, they totally depend on their mother, who will provide the protection and food they will need during the first months or years of life, breast milk.

List of mammalian animals

To better understand these animals, we present an extensive list of examples of mammals, although not as extensive as the more than 5,200 species of mammalsthat currently exist on planet Earth.