What's
the first thing you think of when you hear the word fossil? Dinosaur,
right? A fossil is the remains, trace, or imprint of a plant or animal
that has been preserved in the earth's crust since some past geologic
time. Well, there is fossil evidence for members of my family that belong
to the phylum annelid that you will learn about in my family tree. There
are the thousands of worm-like animals that have segments.
The
problem with our fossils is that we are all soft-bodied and have no
bones. Our fossils are not easy to find and recognize as are the fossil
bones of dinosaurs. Existing fossil annelids date back 500 million years
ago. Some scientists now say that they may have found that some of my
relatives might have lived on earth more than a billion years ago.
The
problem is that scientists haven't found fossils of the worms themselves
but "trace fossils." These are tunnels in rocks that may be
burrows that were formed when the worms wriggled through the sand. Scientists
have found these in India. Not everybody agrees because some think these
"tunnels" were made in other ways.
Most
scientists would agree that annelids, soft-bodied worm-like animals,
appeared during the Cambrian period. Body fossils of soft-bodied worms
are rare, but some places have very good preserved fossils. One of the
better places to find these fossils is Mazon Creek, near downtown Chicago.
Fossils Oligochaeta, which are closer to earthworms, are rare and harder
to find.
