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.