Sammalia

Sammalia is a common misspelling of the scientifically correct term Mammalia, the class of vertebrate animals that includes all mammals. Members are characterized by hair or fur, mammary glands in females that produce milk for nourishing young, and three middle ear bones. Most mammals are warm-blooded (endothermic) and possess a relatively high metabolic rate.

The class Mammalia is traditionally divided into three major lineages: monotremes, marsupials, and placental mammals. Monotremes, such as the platypus and echidnas, lay eggs and lack nipples; milk is secreted onto the skin or fur. Marsupials, such as kangaroos and opossums, give birth to underdeveloped young that typically complete development in a pouch. Placental mammals (eutherians) have a complex placenta that nourishes the developing fetus inside the uterus, allowing longer gestation and more fully developed young at birth.

Anatomically, mammals share features such as a single-bossed jawbone (dentary) and three auditory ossicles (malleus, incus, stapes). Hair and insulating underfur help regulate body temperature, and many species possess sophisticated nervous systems and sensory capabilities, including advanced olfaction and, in some groups, highly developed vision and hearing.

Mammals inhabit nearly all ecosystems, from oceans to deserts and high mountains. They range in size from tiny bumblebee bats to the blue whale, the largest animal ever known. Modern mammals play diverse ecological roles as herbivores, carnivores, omnivores, and omnipresent contributors to pollination, seed dispersal, and soil dynamics.

The fossil record shows mammalian origins in the late Triassic, with major diversification after the extinction event at the end of the Cretaceous. Today, roughly 6,000 species are described.