Unusual Spirograptus Silurian Graptolite Fossil

Spirograptus turriculatus

Phylum Hemichordata, Graptolithina

Geological Time: Early Silurian, Late Llandovery Stage (435-434 million years ago)

Size: 10 mm

Fossil Site: Cotton Formation, Cottons Hill Quarry, New South Wales, Australia

Spirograptus Silurian GraptoliteThis is a specimen of a graptolite whose genus name derives from its spiral shape. Graptolites are colonial animals belonging to the hemichordates. The term originates from the patronymic genus Graptolithus. The Graptoloidea were pelagic, drifting with the currents, and were the most important members of the plankton before dying out in the early Devonian. Many were quite cosmopolitan in distribution, and the limited temporal duration of individual species make them excellent index fossils for correlation of strata and biota from widespread locations.

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