cenozoic miocene mammals epoch million smithsonian began
eocene mauricio uintatherium anton paleogene prehistoric mammal antón
silurian plants facts livescience bagley contributor
cenozoic era landscape facts million years animals mammals ago evolution age paleocene ice tertiary fauna paleogene prehistoric time cretaceous during
eocene fauna epoch marsh burian life cenozoic animals landscape zdenek illustration world period flora prehistoric paleogene mammals middle late 1976
cenozoic periods mammals quaternary tertiary here described dividing