Information about Mammals

Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including those that produce milk, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in the brain.

 Most mammals also possess specialized teeth and utilize a placenta in the ontogeny. The mammalian brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals encompass approximately 5,400 species (including humans), distributed in about 1,200 genera, 153 families, and 29 orders,[1] though this varies by classification scheme. Phylogenetically, Mammalia is defined as all descendants of the most recent common ancestor of monotremes (e.g., echidnas and platypuses) and therian mammals (marsupials and placentals).  Souce Wikipedia