Knowra Mammal Mammal A vertebrate in the class Mammalia, characterized by mammary glands that produce milk for young and, in nearly all species, hair at some stage of life.
Mammary gland : A milk-producing gland found in mammals, specialized for nourishing offspring. Milk production is the defining function behind the class name Mammalia.
Lactation : The production and secretion of milk by mammary glands to nourish offspring. It is the shared reproductive investment that defines living mammals.
Synapsid : A member of the amniote lineage that includes mammals and their extinct relatives. Mammals evolved within Synapsida, not within the reptile line that includes birds.
Platypus : An Australian egg-laying mammal with a flattened bill, webbed feet, and electroreception. It is a living monotreme that combines mammalian traits with egg-laying.
Bird : A feathered, warm-blooded vertebrate in the class Aves. Birds share endothermy with mammals but have feathers rather than mammalian hair.
Hair : A keratin-based structure that grows from the skin of mammals. Hair is a hallmark mammalian trait, even in species with sparse or modified coats.
Placenta : An organ that mediates exchange of nutrients, gases, and wastes between a developing fetus and its parent. In placental mammals, it sustains development inside the uterus.
Cynodont : A synapsid group that includes mammals and close extinct relatives with increasingly mammal-like anatomy. Cynodont fossils document the gradual assembly of mammalian features.
Echidna : A spiny egg-laying mammal native to Australia and New Guinea. Echidnas provide another living example of monotreme reproduction.
Reptile : A vertebrate in the traditional group Reptilia, including turtles, lizards, snakes, and crocodilians. Reptiles are close amniote relatives, but lack mammary glands and hair.
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