Definition of graptolite in English:

graptolite

noun

  • An extinct marine invertebrate animal of the Paleozoic era, forming mainly planktonic colonies and believed to be related to the pterobranchs.

    • ‘In addition, the first planktonic graptolites evolved, though some species of graptolites became extinct.’
    • ‘The Ordovician is best known for the presence of its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates).’
    • ‘To return to our example, the usual biostratigraphic markers in Middle Paleozoic stratigraphy are graptolites, conodont ‘jaw’ parts, and thelodont scales.’
    • ‘The boundary between the Cambrian and the Ordovician is marked by the appearance of planktic dictyonemid graptolites.’
    • ‘Other marine fossils commonly found throughout the Silurian record include trilobites, graptolites, conodonts, corals, stromatoporoids, and mollusks.’

Origin

Mid 19th century: from Greek graptos marked with letters + -lite: so named because of the impressions left on hard shales, resembling markings with a slate pencil.

Pronunciation:

graptolite

/ˈɡraptəˌlīt/