The characteristics that make a mammal a mammal include pres-ence of hair or fur, warm-blooded, young born alive, mammary glands and complex brain. 2. The oldest infraclass of therian mammals is the Metatheria, or the marsupials. Despite sharing some reptilian features, monotremes possess all the major mammalian characteristics, like air breathing, endothermy (i.e., they are warm-blooded), mammary glands, a furred body, a single bone in the lower jaw and three bones in the middle ear. The subclass Prototheria contains the egg-laying mammals, which are the most ancestral forms in the class Mammalia. This subclass includes only one order that is Monotremata. Pinna: Present and is formed by the nasal and … There are about 5,000 species of mammals. 3. Hence, option A is correct. There are three subclasses of mammals: Prototheria, Metatheria and Eutheria. Eutheria. Prototheria comprises of 6 species all in a single order. Mammary: Mammary glands are without nip­ples or teats. There are only five extant species grouped into two families and a single order, the Monotremata. The mammals can lay eggs also. The relatively primitive prototherian reproductive system evidently evolved after their evolutionary line separated from the other early mammals. Order Monotremata : Thesemammals show prototherian char­acters. 1) Prototheria 2) Theria. Monotremata is the only order in the prototheria subclass. Prototheria. Evolution of Mammals and Mammalian Characteristics study guide by Raeleigh_Agan includes 83 questions covering vocabulary, terms and more. Quizlet flashcards, activities and games help you improve your grades. Difference # Prototheria: 1. Monotremes have a reptilian-like shoulder girdle and egg. Is the eutherian mode of reproduction “better” than the metatherian mode? Example: Duckbilled platypus, Echidna. 3. 2) They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. ADVERTISEMENTS: The upcoming discussion will update you about the difference between prototheria and theria. How do marsupials and placental mammals differ in maternal investment via gestation versus lactation? The characteristics of Prototheria are given below: 1) External ear is absent. We determined the exon–intron organization of the cattle DMP1 gene and used this information to amplify by the polymerase … They are known as viviparous. General Classification of Mammals [Image will be Uploaded Soon] Even of the mammals are already classified into class or sub-class. Mammalia has the largest class in the animal kingdom. Ex: 1) Echidna (Spiny ant eater) 2) Ornithorhyncus (Duck billed platypus) 11) Females are egg laying. They can found in Australia, Tasmania and New-guinea. Based on their reproduction, they are classified into three subclasses: Eutheria. Eggs or Young ones : Oviparous ADVERTISEMENTS: 2. In the young stage teeth are present and in the adults horny plates are formed. VOCABULARY gestation period—the length of time a mammal develops inside the mother’s body prior to birth mammals—animals having these External pinnae are absent. Scientists have organized mammals into about 26 orders based on characteristics and structure. Mammals under this subclass give birth to young ones. Classification Of Mammals. This sub-class includes egg-laying mammals. Mineralization of tooth dentin (the deposition of hydroxyapatite crystals in and around collagen type I fibers of the extracellular matrix) requires the involvement of several genes, among them the gene coding for the dentin matrix protein 1, DMP1. Order: Monotremata. ADVERTISEMENTS: 4. Mammalia is divided into two subclasses. Glands: Indistinct or absent. 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