On the decline of the Glacial period, as both hemispheres gradually recovered their former temperature, the northern temperate forms living on the lowlands under the equator, would have been driven to their former homes or have been destroyed, being replaced by the equatorial forms returning from the south.
Glaziaraldiak amore ematean, hemisferio biak poliki-poliki lehengo tenperaturara etorri zirenez gero, ekuatoreko beterrietan bizi ziren iparreko klima epeleko formak, beren sorlekura itzultzea beste erremediorik ez zuten izanen edo, bestela, hegotik hara itzuliriko formek suntsituko zituzten, haien lekua hartuz.