Enigmatic Cretaceous Bristletail Insect Fossil

Thysanura indet

Class Insecta, Subclass Apterygota, Order Thysanura

Geological Time: Lower Cretaceous, Late Aptian-Cenomanian (108-92 million years ago)

Size: 30 mm overall, body 12 mm

Fossil Site: Crato Formation, Nova Olinda Member, Ceara, Brazil

Bristletail Insect FossilDescription: The Araripe Basin of Brazil is home to a fantastic array of exquisitely-detailed Early Cretaceous fossils, some of which have been preserved in three dimensions. While the entire formation has until the last decade or so been termed the Santana Formation, David Martill has separated out the slightly older insect-bearing strata as the Nova Olinda Member of the Crato Formation. Quarrying operations for the purposes of obtaining paving stones exposes the remarkable insect fauna in much the same way that quarrying for lithographic limestone in Solnhofen has afforded a panoply of wonderfully-preserved Jurassic fossils in Germany. In addition to the many orders of insects, spiders, scorpions, decapod crustaceans, and many plants have been found. Interestingly, to date no pterosaurs or terrestrial vertebrates have been found, in stark contrast to the overlying Santana Formation deposits. This fine example shows a bristletail. The Bristletails are members of the Thysanura, a member of the Sub-Class Apterygota, or wingless insects. They are thought to be the most primitive of insects, and may never have had wings throughout their evolutionary history. Interestingly, while they are of primitive design, the fossils of the Crato Formation are the oldest known examples, rather than the Devonin, leaving a gap of nearly 280 million years in the fossil record of the order.

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