The egg consists of a hard protective outer shell. There are only two mammals that are oviparous; the platypus and four species of echidnas. There are only five known monotremes mammals on the planet, with the platypus and echidna’s being the most well … Such animals are called egg-laying animals. Inside the shell in the centre is a yellow portion called the yolk. Chimpanzee _____ are mammals whose young are born at a very early stage development- they usually continue to develop in a pouch on their mother's body. False. These are the platypus and four species of echidna or spiny anteater. The class Mammalia is divided into two subclasses based on reproductive techniques: egg-laying mammals (yinotherians or monotremes - see also Australosphenida), and mammals which give live birth ().The latter subclass is divided into two infraclasses: pouched mammals (metatherians or marsupials), and placental mammals (eutherians, for which see List of placental mammals). Monotremes ( monotremata) are a unique group of mammals that lay eggs, unlike placental mammals and marsupials, who give birth to live young. There are only five surviving monotreme species and all can be found in either Australia or New Guinea. 1. 2 Rare Mammals That Lay Eggs Instead Of Giving Birth To Live Young. Yet anything is possible, and mammals that lay eggs do exist. Marsupials are mammals that lay eggs. The eggs are leathery like many reptile eggs, rather than brittle, like the eggs of chickens and other birds are. Elephant 2. Monotremes include several species of echidnas and the platypus. The only mammals that lay eggs are known as monotremes. In some ways, monotremes are very primitive for mammals because, like reptiles and birds, they lay eggs rather than having live birth. Fish, snakes, turtles, frogs, birds etc. Marsupial. The young hatch about 10 days after the eggs are laid. are egg-laying animals. Fertilization is either internal or external but the eggs hatch in an external environment and not in the mother's womb. INstead, animals like the platypus and echindnas actually lay eggs. After a certain period, their young ones come out of the eggs. Laura Klappenbach, M.S., is a science writer specializing in ecology, biology, and wildlife. They also hatch the eggs. Oviparous animals include birds, reptiles, amphibians, and fish. There are around 5000 species of mammal. According to the logic of nature, mammals are supposed to give birth to live young. The only mammals that lay eggs are known as monotremes. Monotremes reproduce in a much different way than most other mammals do. Monotremes are egg laying mammals. It is a normal thing for mammals to not lay eggs, but it is a rare and unique case when they do lay … The vast majority of mammals give birth to live young. There are four extant species of echidnas which together with the duck billed platypus are the only surviving members and are the only extant mammals that lay eggs. In addition, they lay eggs rather than bearing live young, but like all mammals, the female monotremes nurse their young with milk. A rare and unusual category of mammal birth where the animal lays eggs. An A-Z of Mammals with links to further information about them. Oviparous animals are animals that lay eggs. But here is a complete list of animals which lay eggs. The biggest difference is that they lay eggs rather than giving birth to live young. Name two placental mammals. In a number of other respects, monotremes are rather derived, having highly modified snouts or beaks, and modern adult monotremes have no teeth. The monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts compared to the more common mammalian types. The Three Different Types of Mammal Births Monotremes. The list below represents the most commonly known mammals grouped bothalphabetically and by classification group.. Click on a mammal for facts about that mammal.