graptolite
/ˈɡraptəlʌɪt
/noun
A fossil marine invertebrate animal of the Palaeozoic era, forming mainly planktonic colonies and believed to be related to the pterobranchs.
- Class Graptolithina, phylum Hemichordata.
- Other marine fossils commonly found throughout the Silurian record include trilobites, graptolites, conodonts, corals, stromatoporoids, and mollusks.
- To return to our example, the usual biostratigraphic markers in Middle Paleozoic stratigraphy are graptolites, conodont ‘jaw’ parts, and thelodont scales.
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.