Class Mammalia

∞ generated and posted on 2016.11.08 ∞

Formal name for the taxon consisting of hairy animals that produce and feed their young milk.

Extant mammals consist of monotremes, marsupials, and eutherians (the latter the placental mammals).

Class Mammalia

Figure legend: Mammals have hair/fur, mammary glands, well-differentiated teeth, distinctive skull morphology (synapsids). Most though not quite all mammals also bear their live young. The pictured mammal possesses all of these attributes. Photo taken in 2008 in Georgia (i.e., the country of) near or on the base of Mount Kazbek, which is just over 5,000 meters tall.

The mammals are descendants of mammal-like reptiles, amniotes which roamed the Earth since before the dinosaurs. Mammals became the dominant land vertebrates – and indeed the largest of extant land animals – when the dinosaurs experienced a mass extinction approximately 65-million years ago (the Cretaceous mass extinction), thus opening up an adaptive zone for mammals.