Biology » Vertebrates » Mammals

Summarizing Mammals


Mammals in general are vertebrates that possess hair and mammary glands. The mammalian integument includes various secretory glands, including sebaceous glands, eccrine glands, apocrine glands, and mammary glands. Mammals are synapsids, meaning that they have a single opening in the skull. A key characteristic of synapsids is endothermy rather than the ectothermy seen in other vertebrates.

Mammals probably evolved from therapsids in the late Triassic period, as the earliest known mammal fossils are from the early Jurassic period. There are three groups of mammals living today: monotremes, marsupials, and eutherians. Monotremes are unique among mammals as they lay eggs, rather than giving birth to young. Eutherian mammals are sometimes called placental mammals, because all species possess a complex placenta that connects a fetus to the mother, allowing for gas, fluid, and nutrient exchange.


apocrine gland

scent gland that secretes substances that are used for chemical communication


single bone that comprises the lower jaw of mammals


refers to the possession of two sets of teeth in a lifetime

eccrine gland

sweat gland

eutherian mammal

mammal that possesses a complex placenta, which connects a fetus to the mother; sometimes called placental mammals

heterodont tooth

different types of teeth that are modified for different purposes


one of the groups of endothermic vertebrates that possesses hair and mammary glands

mammary gland

in female mammals, a gland that produces milk for newborns


one of the groups of mammals that includes the kangaroo, koala, bandicoot, Tasmanian devil, and several other species; young develop within a pouch


egg-laying mammal


clade that includes the duck-billed platypus

sebaceous gland

in mammals, a skin gland that produce a lipid mixture called sebum


clade that includes the echidna or spiny anteater

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