Index fossils are remnants of life which existed during limited periods of geologic time, and are useful as guides to dating rocks that they’re found in. #FossilFriday pic.twitter.com/5OJoURy5Eh— USGS (@USGS) 5 Juli 2019
Index fossils are remnants of life which existed during limited periods of geologic time, and are useful as guides to dating rocks that they’re found in. #FossilFriday pic.twitter.com/5OJoURy5Eh