Marine Worm Jaws Marine worm jaws are easily preserved and are
known in nearly every system. Most are composed of chitin
(fingernail material). They are black and shiny, and have many
teeth. Sea worms live today, and the fossil record of worm
trails goes back to Precambrian time. The oldest worm jaws are
found in Ordovician rocks, but they are most common in the
Silurian rocks of northeastern Illinois. Most are so small that
they can only be identified with a magnifying glass. The numbers
in the image below, 8x, 10x, etc., indicate the magnification
needed to see the jaws at the size shown. The printed version of
Guide for Beginning Fossil Hunters can be purchased from the
Shop ISGS Web site. Updated 09/26/2011 SLD