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 Hemiauchenia, and possibly the Vicuña as a proxy for Palaeolama. These species would live in the arid regions and grasslands of North America. Free-ranging camels face predators typical of their regional distribution, which include wolves and lions. The main predator of guanacos and vicuñas is the cougar. During the Pleistocene, a species of tapir existed in North America with many regional variants. They became extinct at the end of the Pleistocene era, but their relatives survive in Asia and South America. The mountain tapir would be an excellent choice for rewilding humid areas, such as those near lakes and rivers.