Dating services in costa mesa
85, 1945) provides systematics of mammal origins and relationships that were universally taught until the end of the 20th century.
Since Simpson's classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics.
The line following the stem group Sphenacodontia split-off several diverse groups of non-mammalian synapsids—sometimes referred to as mammal-like reptiles—before giving rise to the proto-mammals (Therapsida) in the early Mesozoic era.
The modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, and have been among the dominant terrestrial animal groups from 66 million years ago to the present.
Mammals can organize themselves into fission-fusion societies, harems, and hierarchies, but can also be solitary and territorial.
Most mammals are polygynous, but some can be monogamous or polyandrous.
Much of the changes reflect the advances of cladistic analysis and molecular genetics.Mammals include the largest animal on the planet, the blue whale.