Mammalian

Mammalian is an adjective referring to mammals, the vertebrate animals of the class Mammalia. Members of this group share certain derived traits that distinguish them from other amniotes. Most are endothermic, have hair or fur, and females possess mammary glands that produce milk for their offspring. A key auditory adaptation is the presence of three middle ear bones (the malleus, incus, and stapes). The skulls of mammals generally show a secondary palate and differentiated teeth, though tooth patterns vary widely across species.

Mammals are divided into three major lineages: monotremes, marsupials, and placental mammals (eutherians). Monotremes, represented today by the platypus and echidnas, lay eggs. Marsupials give birth to relatively undeveloped young that typically continue development in a pouch. Placentals constitute the largest group and transport nutrients to a developing embryo via the placenta.

The evolutionary origin of mammals traces back to synapsid ancestors in the late Paleozoic, with the mammalian body plan becoming prominent in the Mesozoic era. Modern mammals inhabit nearly every habitat, from oceans to deserts to forests, and include a wide range of sizes and lifestyles, such as bats, whales, primates, and rodents. The term mammalian is widely used in comparative anatomy, physiology, paleontology, and ecology to describe traits shared by mammals or specific taxa within the class.