These are fossils, but not the actual remains of organisms. They are the
"trace fossils" (also called "ichnofossils") of animals feeding as they
moved on or through sediment on the ocean bottom. This one is probably a
"helminthoida," which is a trace fossil produced by an organism when it
grazes. Helminthoida fossils are not uncommon in sedimentary rocks
deposited in deep sea water where sediment-bearing currents flow.
This was probably created by a worm-like animal. But there are many
of kinds of such animals that all could have produced the same pattern,
so it is hard to know exactly what worm was crawling here millions
of years ago when this fossil was created.
