Placentals: what are they, characteristics, classification and examples

We begin by clarifying what placental mammals are , also simply called placental animals. Thus, placental animals constitute a taxonomic infraclass (Placentalia) within the broad class that mammals make up . The females of these species of placental animals have an internal morphological structure in their bellies, called placenta , which guarantees the protection and feeding of the embryos during their gestation period.

This amazing feature is contrary to the outer marsupium that characterizes the other subclass (Marsupials) included within the class of mammals. If you want to know them better, we encourage you to take a look at this other post on What are marsupial animals and examples .

Let’s see in the next sections more characteristics related to placental animals, as well as their classification and many examples to get to know them more closely.

Placental animals are the viviparous mammals par excellence, that is, the largest and most developed group within mammals. Among the main characteristics of placental mammals are:

• The embryo grows inside the mother’s uterus for a long period of time, with the placenta in charge of guaranteeing it food from the mother, as well as protection and the ideal environment for its correct development.
• The females of these types of animals have the heat or estrous cycle , which allows the body to be prepared for copulation, fertilization and the gestation of the offspring.
• They also have mammary glands that allow them to produce the milk that the young need to take from birth to develop and grow until they switch to their final diet.
• These animals have different types of food , there are carnivores, herbivores and omnivores .
• Throughout their life, they have two different types of teeth , the first during the childhood phase and the next in the adult phase.
• Placental animals do not have a cloaca, but rather an excretion system connected to the digestive system and isolated from the reproductive one.
• Placental animals have fur , either denser and thicker or less and thinner, and they can have it always or in some stages of their life, as well as all over the body or only in some parts.
• Likewise, they have sweat glands distributed throughout different areas of the body that allow them to sweat and thus facilitate the regulation of temperature and the elimination of toxins from the body.
• The brain of placental animals has large cerebral hemispheres , as well as a corpus callosum that connects both hemispheres, thus guaranteeing a very advanced development of cognitive functions.
• They have a synapsid skull , which means that it has a lower temporal fossa which is an opening located behind the eye sockets. This fossa in the skull allows it to be lighter and the muscles of the lower jaw to be inserted in this area, facilitating its movement to feed, make sounds, bite, etc.
• Regarding other common morphological characteristics, it is worth noting how the most primitive placentals were small, as well as having very short legs with five fingers and a tubular skull. However, at present, due to the changes that the different types of placental animals have undergone along their evolutionary lines, these common characteristics are more difficult to appreciate.

We also recommend that you learn more about these animals with this other AgroCorrn post about Viviparous Animals: what they are, characteristics and examples .

At present, the classification of placental animals follows a phylogenetic approach based on the biomolecular and genetic results of the species, which allow grouping each and every one of the placental animals that exist (or existed) on the planet following the following classification:

• Cingulados
• Pilosos
• Tubulidentados
• Macroscélidos
• Hiracoideos
• Proboscídeos
• Sirenians
• Eulipotiflanos
• Chiroptera
• Folidotes
• Carnivores
• Perisodactyls
• Cetaceans
• Artiodáctilos
• Lagomorfos
• Rodents
• Scandents
• Primates

If you want to read more articles similar to Placentals: what they are, characteristics, classification and examples , we recommend that you enter our Biology category .