Pleistocene The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils: "Discoaster pentaradiatus" and "Discoaster surculus". The Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has, in the past, been used to mean the last ice age. The revised definition of the Quaternary, by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene. The modern continents were essentially at their
Pleistocene rewilding Homotherium), the American lion, dire wolf, and the American cheetah. Some carnivores and omnivores survived the end of the Pleistocene era and were widespread in North America until Europeans arrived, such as grizzly bears, cougars, jaguars, grey and red wolves, bobcats, and coyotes. The cheetah could serve as a substitute for "Miracinonyx", keeping the population of pronghorns in check. Jaguars could be reintroduced back to areas of North America to control populations of prey animals. Some of the larger cats such as the African lion could act as a proxy for the Pleistocene American lion, they could be introduced to