Wenlock Series lagerstätte

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The Silurian lagerstätte preserved in the limestone Wenlock Series of Herefordshire, England, offers paleontologists a rare snapshot of a moment in time, about 420 Mya. In the formation, layers of fine-grained volcanic ash punctuate a sequence of carbonate muds that were accumulating in a marine environment on the outer continental shelf. In this fine-grained matrix, soft-bodied animals and delicate, lightly-sclerotized chitinous shells are often preserved in three dimensions, as calcitic fossilizations within calcareous nodules. Calcitic fossilization is an unusual feature.

The lagerstätte, discovered and first published in 1996, provides a wider representation of organisms than a conventional fossilizations of shelly and bony elements. The Wenlock Series offers a diverse macrofauna that includes polychaete worms (Kenostrychus), sponges, graptolites, a chelicerate (Offacolus) and a vermiform mollusc (Acaenoplax). On the microscopic scale the diverse microfauna includes abundant well-preserved radiolarians.

The delicate Wenlock fossils are difficult to separate from split sections, so Mark Sutton and his team have devised a method of serially grinding sections; from digital photographs three-dimensional "digital fossils" are reconstructed from datasets.

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