any extinct Palaeozoic colonial animal of the class Graptolithina, usually regarded as related to either the hemichordates or the coelenterates: a common fossil, used to determine the age of sedimentary rocks
Word origin
C19: from Greek graptos written, from graphein to write + -lite
Examples of 'graptolite' in a sentence
graptolite
Fossils other than graptolites are very rare.
Richard Fortey THE EARTH: An Intimate History (2004)