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Meaning of graptolite

grap•to•lite

Pronunciation: (grap'tu-līt"), [key]
— n.
  1. any colonial animal of the extinct class Graptolithina, most common in the Ordovician and Silurian Periods, thought to be related to the pterobranchs.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.