Synapsids - mammals and their extinct relatives


Sarcopterygii; Tetrapoda; Amniota; Syanpsida


The primary dichotomy within the amniotes is that between the Reptilia, or Sauropsida (see amniote groups above - turtles through to birds), and the Synapsida, thought to have diverged sometime during the Carboniferous (approx. 360 - 300 million years ago). Thus, the Synapsida is one of the two major lineages of amniotes, containing the mammals plus all extinct amniotes more closely related to mammals than to reptiles.

The following webpages outline the diversity of the living representatives of the
synapsids - the class Mammalia. The extant mammals are divided into three major lineages:

  • Monotremata - monotremes
  • Marsupialia - marsupials
  • Eutheria - placental mammals


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