Gourt > Science > Biology > Developmental Biology > Model Organisms > Mammalian
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 endothermic or "warm-blooded" bodies. The brain regulates endothermic and circulatory systems, including a four-chambered heart. Mammals encompass some 5,500 species (including Humans), distributed in about 1,200 genera, 152 families and up to 46 orders, though this varies with the 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).
Mammal anatomy
Skeletal system
The vast majority of mammals have seven cervical vertebrae (neck bones), including bats, giraffes, whales, and humans. The few exceptions include the manatee and the two-toed sloth, which each have only six cervical vertebrae, and the three-toed sloth with nine cervical vertebrae. More on [ Mammal ]
Comparative Placentation - Provides an examination and evaluation of placenta from many different types of mammals. Includes glossary, taxonomy and biography of author, maintained by the University of California, San Diego.
Meta Description: [ kurt benirschke, comparative placentation, placenta ]
Edinburgh Mouse Atlas Project - Computer modeling of stages of mouse embryogenesis to map the expression of different genes. 3D Embryo Anatomy Atlas and gene expression database at MRC Human Genetics Unit, Edinburgh.
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