Mammals that lay eggs

Mammals are a class of animals characterized by being vertebrates, being covered with hair, being of warm blood, possess milk-producing mammary glands that allow feeding their young, and be viviparous. These are the common characteristics of mammals, but in some cases the latter is not fulfilled, in those cases the animals are oviparous, that is, their reproduction is based on eggs. These oviparous mammals they make up a unique class of animals, being the most curious mammals. To understand these special species, today in this lesson from a TEACHER we are going to talk about the egg-laying mammals.

The name given to egg-laying mammals is monotremes. The monotremes or monotremes are an order of current mammals that maintain some primitive characteristics, retaining some reptilian characteristics such as its oviparous reproduction or the cloaca, a hole that only monotremes and marsupials have in mammals.

The monotremes are made up of 5 species currently they are the following:

• Platypus: It is a mammal
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  semi-aquatic that lives in Australia and on the island of Tasmania. It has a very strange appearance, with a duck-shaped snout, beaver's tail and otter feet, which led European naturalists to think that it was some kind of forgery. It is also one of the few poisonous animals in the world.
• Short-nosed echidna: It is a species that inhabits Australia, and is characterized by having a body wrapped in spikes, a short snout, and a tongue to be able to hunt at high speed. It is the most widespread native animal throughout the country.
• Attenborough's long-nosed echidna: It is one of the three species of long-snouted echidna that we can find in the world. Lives in Papua New Guinea, and is in a critical state of conservation.
• Eastern long-nosed echidna: Another species of long-nosed echidna. It also lives in Papua New Guinea, but in the easternmost part of the island.
• Western long-nosed echidna: It lives in the western part of Papua New Guinea, and like the other two species mentioned is in a critical conservation situation.

Being an order with such curious and strange characteristics, does not make it up to many kinds of animals. Being the animals that are part of the order, all from a very close area, and most closely resembling each other, the platypus being the most different.

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To continue with this lesson on which mammals lay eggs, we must talk about the characteristics that monotremes possess. Due to their reptilian characteristics, monotremes share characteristics with both mammals and other species of animals, such as reptiles. Some of the characteristics that monotremes share with the rest of mammals are the following:

• Your skin is covered with hair.
• Have diaphragm, a tissue responsible for the respiration of the animal.
• The heart is divided into four chambers.
• They have three bones in the middle ear.
• Even being oviparous, they produce milk to feed their newborn young.
• They are homeotherms, that is, they are able to maintain their body temperature within limits.

On the other hand, monotremes have certain characteristics that distinguish from other classes of mammals, among which we can include:

• They are oviparous, that is to say, its reproduction is based on the eggs.
• They have a complex pectoral girdle, and a skull with characteristics of extinct mammals.
• They have a hole called sewer, in which the urinary, digestive and reproductive tracts converge.

Monotremes are one of the orders that arouse the most curiosity, because they are animals with very special characteristics. To satisfy your interest, we are going to tell you some curiosities about these very special animals.

• Monotremes produce milk, but have neither breasts nor nipples, because of this expel the substance through the skin.
• It's almost blind and deaf, having a very peculiar way of hunting due to this.
• They live only in Papua New Guinea, Australia and on the Island of Tasmania, being a species much visited by tourists.
• The platypus is one of the few poisonous mammals that exist, but this characteristic is only found in males.
• Monotremes can live up to 50 years.

Image: Slideplayer