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Fossils: Evidence of Change

Ammonite uncovered near Fort Stockton, Texas

 

About 500 million years ago, during much of the Paleozoic Era, great oceans covered the world. Over time, sponges, algae and other lime-secreting marine organisms slowly built the limestone reefs now characterized as mountain-like mesas and plateaus. Scientists believe that this area of the United States was still a thriving marine ecosystem about 245 million years ago during the Permian Period, however, waters receded and the ecosystem changed. Shells and other remnants of ancient creatures that once lived in the ocean can be found imbedded within the fossil rich landscape that creates the Trans-Pecos region of West Texas.

Dinosaurs didn't yet exist in the Permian, however, herbivorous and carnivorous animals that eventually evolved into mammals did roam this area. Famous Permian fossil-bearing sites include Texas' Glass Mountains, Texas' and New Mexico's Guadalupe Mountains, and even in some parts of Germany.

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Great reefs flourished in Permian seas. Among the most famous are the reefs that today make up much of Texas' Guadalupe Mountains National Park and neighboring Carlsbad Caverns in New Mexico. In fact, much of the world's petroleum reserves were formed during the Permian Period.

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