graptolite

graptolite (n.)fossilized colonial animal from the Cambrian and later, 1838, from Modern Latin graptolithus, literally "written-stone," from Greek graptos "engraved, written, painted" (verbal adjective of graphein; see -graphy) + lithos "stone" (see litho-). So called because the fossils resemble pens. Related: Graptolitic.