The Blattaria includes the roaches, from the six-inch tropical roaches of South America to their small cousins that are probably tiptoeing through your kitchen right now. There are about 4,000 species worldwide.
Roaches arose in the Pennsylvanian period, about 280 million years ago, and have not changed much since. Compare the photograph of the living cockroach at the top of the page with this picture, depicting the 260 million-year-old, three-inch fossil roach Mylacris, and you'll see that roaches have not undergone any sweeping changes in their form in all that time, a phenomenon known to evolutionary biologists as stasis.
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