Resize Text: Today, Arizona is known for its desert climate, with hot summers and mild winters. It is hard to imagine that millions of years ago the majority of this state was covered by shallow seas. At that time, these seas teemed with life, including abundant fish and large, extensive coral reefs. Now, fossilized remains of this fauna are all that exist, but they tell a unique story of the life, climate, appearance, and history of Arizona millions of years ago.
Geologic History
The Devonian Period of the Paleozoic Era lasted more than 60 million years, from 417 million years ago (Ma) to 354 Ma. Around this period, important and dramatic changes were occurring in the global land masses. In the late Silurian and lower Devonian, the combined land masses of Baltica and Avalonia collided progressively with Laurentia (modern-day North America and Europe), forming the large continent of Euramerica. This resulted in the formation of the Acadian Mountains, predecessors of the Appalachian Mountain Range (fig. 1A) (Blakey 2010). A second major land mass, Gondwana, was made up of what is currently South America, Africa, Antarctica, India, and Australia (fig. 1A). These two large land masses existed close to one another with a major portion of the land mass near the equator. This region near the equator provided an area during the Devonian that maintained a relatively warm climate, and these warmer temperatures were particularly beneficial for plant life.
Jeffrey Langland has a doctorate degree in microbiology and is employed as a faculty member at Arizona State University and the Southwest College of Naturopathic Medicine. He has been an avid fossil and mineral collector in Arizona for more than thirty-five years.
Edith Langland has a master's degree in molecular biology and a master's degree in education and is employed as a science teacher in the Scottsdale school district in Arizona. With her husband, she has been collecting Arizona fossils for over ten years.
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