By: Michael Peterson
California was once home to the American Lion, short-faced bear, and dire wolf. Yet these large, exciting predators are now extinct. So, how do we know they ever existed? The hard structure of their bones and the right conditions produced petrified impressions of past animals known as fossils, which are found in the rock where they were preserved. Even more valuable are natural asphalt seeps, such as the La Brea Tar Pits in Los Angeles, which served as a bizarre trap for large animals and an ideal preservation environment. The abundance of fossils in this one spot, including over four hundred dire wolf skulls, has provided researchers with a treasure chest of evidence to reconstruct a past era of animal diversity.
Vertebrates, including birds and mammals, have large bones that increase the chances that they may be preserved, making it possible for us to find and describe the history of these creatures. But how do we know about the rest of the earth’s species? The little ones, the squishy ones, the ones that live in water and get washed away? How do we know what invertebrates, the spineless ones, once existed?
Many times, our best clues of extinct invertebrate biodiversity are provided by the investigations and notes left behind by earlier scientists. A variety of century-old biological surveys exist, as do species descriptions and fishing records. For more recent time periods, photos of wildlife or landscapes may exist. These records provide clues that enable a historical approach to ecology and how the richness of species may be changing over time.
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