• The earliest mammals evolved from cynodonts.
  • Mammals continued to evolve.
  • Monotreme mammals probably split off from other mammals first.
  • They were followed by marsupials.
  • Placental mammals probably evolved last.
  • Early monotreme fossils have been found in Australia.
  • An example is a genus called Steropodon, shown in Figure below.
  • It may have been the ancestor of the platypus.
  • The ancestor of placental mammals may be the extinct genus Eomaia.
  • It was a tree climber and probably ate insects and worms.
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