Everyone is familiar with porcupines, beavers, rats, squirrels, and, of course, mice—common representatives of the order Rodentia or the rodents. They are defined by zoologists as having a single pair of constantly growing upper and lower jaw incisors. Over 40 percent (about 1,700) of mammal species are rodents.

by Frank Sherwin, M.A., & Brian Thomas, M.S. *

When geologists make field observations, they typically focus on the rock before them and its color, density, mineral makeup, fossil content, and other features. But they often would be well-served by looking at the strata’s context as well.