Mammal

The mammals are the class of vertebrate animals characterized by the presence of mammary glands, which in females produce milk for the nourishment of young; the presence of hair or fur; and which have endothermic or "warm-blooded" bodies. The brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals encompass some 5500 species, distributed in about 1200 genera, 152 families and up to 46 orders, though this varies depending on the classification scheme adopted.

External link

• North American Fossil Mammal Systematics Database.
• Paleocene Mammals, a site covering the rise of the mammals
• Evolution of Mammals, a brief introduction to early mammals
• The Evolution of Mesozoic Mammals, a Rough Sketch, an informal introduction
• Carnegie Museum of Natural History, some discoveries of early mammal fossils
• Mammal Taxonomy, database of mammals of the world, updated each month
• Mammal Species of the World, searchable online version of 2nd edition (1993) of Mammal Species of the World