The world鈥檚 oldest known insect has been found lurking in a fossil-filled vault under a museum. The finding pushes back the origins of winged insects by 80 million years, and could shed light on the mystery of why the ability to fly first evolved.
The fossilised creature, Rhyniognatha hirsti, is 400 million years old and comes from near Aberdeen, Scotland. The Australian entomologist Robin John Tillyard studied it in the 1920s and reported that it might be related to insects, but he could not be sure.
Since then, experts largely accepted Tillyard鈥檚 suggestion that the fossil is unremarkable, and it was left undisturbed in the vaults of London鈥檚 Natural History Museum.
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But while at the museum gathering photos for a book on insect evolution, two US entomologists stumbled on the Rhyniognatha fossil and looked at it under a microscope. 鈥淭oday, our microscopes are vastly better than what Tillyard was using,鈥� says Michael Engel, of the University of Kansas in Lawrence. 鈥淎nd when we looked through the scope, we were stunned.鈥�
Engel, with David Grimaldi of New York鈥檚 American Museum of Natural History, saw that Rhyniognatha has all the hallmarks of a true insect. Far from being a primitive type, it chewed food with efficient scissor-like jaw mouthparts, or mandibles, with two joints.
Boiling water
Its mandible structure is only ever found in winged insects, which is compelling evidence that Rhyniognatha could fly, even though wings do not appear on the fossil. 鈥淭he fossil came from hot springs, and unfortunately, boiling water is not a good place for a wing to be preserved,鈥� Engel notes.
Until now, the oldest insect fossils on record were a primitive pair of wingless insects 379 million years old, found in New York State and Canada. Winged insects were thought to have evolved later, some 320 million years ago. But Rhyniognatha suggests insects were flying at least 400 million years ago.
Pushing back the evolutionary origins of insects could help explain why they have become so dazzlingly diverse. 鈥淓ven just the known insect species outnumber all other living things combined,鈥� says Engel.
It could also hint at why insects started to fly. Shortly before Rhyniognatha lived, the world鈥檚 plants had sprouted from dwarfs no more than a metre high into giants more than 30 metres tall. It is possible that insects coped with the new environment by learning to glide from treetops to the ground.
Engel now hopes to trawl the world鈥檚 famous fossil sites to find more insects as old as Rhyniognatha. 鈥淲e would absolutely die to have an entire bug with wings from that period, we could learn so much from their structure.鈥� Journal reference: Nature (vol 427, p 627)