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FIGURE 6.—Distribution of late Blancan to early Irvingtonian (ca. 2.5-1.0 Ma) local faunas in North America.
Size of dot or circle indicates number of species of mammals of South American origin (Xenarthra, Caviomorpha)
in the fauna. Local faunas include those listed in Table 3 plus Wellsch Valley, Saskatchewan; Delmont, South
Dakota; Big Springs, Nebraska; Kentuck, Kansas; and Anita, Arizona. Arrows signify likely corridors of dispersal;
the Gulf of Mexico terrestrial corridor would have been widened onto the continental shelf during glacial
periods.
these taxa suggests that the Gulf Coast corridor was composed
of a mosaic of communities, including dry thorn-scrub, hammocks,
and aquatic zones (lakes and wetlands). Such a broad
zone having patches of dry to moist habitats is unlike any such
region today and probably developed in response to unusual climatic
conditions during glacial intervals in the Plio-Pleistocene.
Conclusion
The record of birds in North America during the Great
American Biotic Interchange indicates patterns for timing and
dispersals that are similar to those known for other vertebrates
and for plants. As with the mammals, the birds are largely
presumed to represent a xeric, thorn-scrub and savannah envi-