Nesbitt Memorial Library Journal, Volume 10, Number 2, July, 2000 Page: 77
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The Ice Age Megafauna of Colorado County, Texas
by Rollin H. Baker
The history of life on earth is divided into three eras: the Paleozoic, Mesozoic,
and Cenozoic. The Paleozoic, which is the earliest of the three, and the Mesozoic, during
which dinosaurs roamed the earth, each ended with mass extinctions of most of the earth's
living creatures. Because the ocean did not recede from Colorado County until the Cenozoic
era, no fossils from land-roving creatures from earlier eras can be found in the county. The
three great eras of life on earth are subdivided into periods and epochs. The two most recent
epochs, both obviously in the Cenozoic era, are the Pleistocene and the Holocene. The
Pleistocene lasted for hundreds of thousands of years and featured a series of ages-long
moderate climates alternating with extensive colder climates. When the latter conditions
prevailed, massive continental glaciers covered vast parts of North America and Eurasia.
The last of these glacial events, named the Wisconsin, began to melt away about 15,000
years ago. At about that time, ancient groups of terrestrial mammals, many of them large in
stature, plus other forms of life, suddenly disappeared from the fossil record. This dramatic
extinction is one of the events which marks the end of the Pleistocene and the beginning of
the Holocene, the epoch in which we now live.'
Colorado County's Environment in Ancient Times
During the thousands of years marking the end of the Pleistocene Ice Age and
present Holocene times, the physical properties (physiography) of the Gulf Coastal Plain of
which Colorado County is a part, remained much the same as it is today. This region was
well to the south of the southernmost glacial intrusion into what is now our north-central
states. Still, the massive ice mass, measuring in some places more than a mile thick, must
have provided Colorado County and its flora and fauna with a pronounced chilling effect.
This colder and probably moister environment certainly encouraged some forms of life and
discouraged others. One would suspect that frigid conditions prevailed when glacier-cooled
winds swept directly from the northern ice fields across the Texas Gulf Coastal Plain. Prob-
ably, our present-day northers (nortes) are rather mild when compared with prehistoric
1 R. S. Toomey IW, M. D. Blum, S. Valastro, Jr., "Late Quaternary Climates and Environments of the
Edwards Plateau, Texas," Global and Planetary Change, vol. 7, 1993, pp. 299-320.
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Nesbitt Memorial Library. Nesbitt Memorial Library Journal, Volume 10, Number 2, July, 2000, periodical, July 2000; Columbus, Texas. (texashistory.unt.edu/ark:/67531/metapth151409/m1/13/?q=nesbitt%20memorial%20library%20journal: accessed October 22, 2017), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; crediting Nesbitt Memorial Library.