Graptolite

Part of speech: noun

Definitions

1. A fossil of an extinct colonial marine animal found in Paleozoic rocks, often appearing as thin serrated lines on shale
2. An extinct sea-dwelling colonial organism whose preserved remains look like small toothed markings pressed into ancient stone
3. The fossilized remnant of a primitive colonial marine creature that lived during the Paleozoic era and is used to date rock layers

Etymology: Graptolites are fossil marine colonial animals, and their name describes what they look like: the fossils resemble faint pencil marks or writing on rock. The name combines the Ancient Greek "graptós," meaning "painted" or "marked with letters," with the English suffix "-lite," from Greek "lithos," meaning "stone." Together they produce a term for "writing-stone" or "marked stone." The Greek adjective "graptós" comes from "gráphō," "to write, scratch, or paint," which is also the source of familiar English words such as "graph" and "-graphy." The same root gives "graphite," the soft form of carbon whose name refers to its use in marking, a pairing that makes graptolites a close cousin of pencil lead in both name and appearance.