graptolite

[ grap-tuh-lahyt ]

Phonetic (Standard)IPA

noun

any colonial animal of the extinct class Graptolithina, most common in the Ordovician and Silurian Periods, thought to be related to the pterobranchs.

graptolite

/ ˈɡræptəˌlaɪt /

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

graptolite

/ grăp′tə-līt′ /

Any of numerous hemichordates of the class Graptolithina. Graptolites form colonies consisting of interlocked cuplike chambers arranged in one or more branches and covered by an exoskeleton. They flourished from the late Cambrian to the early Mississippian Period, and were thought to be extinct until 1992 when scientists discovered what is believed to be a living species. Graptolites are important index fossils used to date the rocks of the Silurian and Ordovician Periods.

1830–40; < Greek graptó ( s ) painted, marked with letters (verbal adjective from gráphein to write) + -lite

C19: from Greek graptos written, from graphein to write + -lite

The strata consist of greywackes, flags and shales with seams and zones of graptolite shale which yield fossils sparingly.

A typical graptolite consists of an axis bearing a series of tooth-like projections, like a saw.

The genus Bryograptus, a many-branched graptolite, also appears to characterise this fauna.

These consist of greywackes, flags and shales with bands of dark graptolite shales, the finer sediments being often well cleaved.

April 19, 2024tortuous

[tawr-choo-uhs ]

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