Abundant paleontologic evidence proves that Tertiary terrestrial vertebrates, particularly mammals, moved between the Old and New words across a land dispersal route located somewhere in the Northern Hemisphere, probably in the vicinity of the present Bering Strait (Hopkins, 1959; Matthew, 1939; Savage, 1958; and Simpson, 1947). Matthew (1939) proposed that Tertiary mammals evolved most actively in the northern Holarctic region, sending waves of successively more progressive mammals southward into the continental “prongs.” Thus the most progressive Tertiary mammals at any given time generally would have occurred in the climatically more rigorous northern part of the...
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