Close cousins of modern woodlice were crawling across what’s now Ireland some 360 million years ago, according to newly published fossil research.

The fossil arthropod was first recovered in 1908 from the Late Devonian floodplains of Ireland, but until now, scientists had failed to identify the species.

Using powerful imaging technology, researchers were able to render the ancient woodlice in 3D. They also performed a phylogenetic survey of related crustacean classes, including krill and decapods.

The analysis, published Wednesday in the journal Biology Letters, revealed the Oxyuropoda species to be the oldest member of the suborder Peracarida, a large group of malacostracan crustaceans consisting mostly of woodlice and side-swimmers.

“Woodlice, and their relatives form a group of crustaceans named peracarids that are as species-rich as the more famous group comprising krill, crabs and shrimps named eucarids,” lead study author Ninon Robin said in a press release.

“From their ancestral marine habitat some peracarids have, unlike eucarids, evolved fully terrestrial ground-crawling ecologies, inhabiting even commonly our gardens, for example pillbugs and sowbugs, which are very common in Ireland,” said Robin, a postdoctoral researcher at University College Cork.

Tiny crustaceans are small and delicate. As such, ancient fossil specimens are hard to come by. However, scientists had previously estimated that the cousins of woodlice likely originated a few hundred million years ago.

“From previous genomic and molecular studies, scientists had suggested that this group of crustaceans must have appeared around 450 million years ago,” Robin said.

The latest research confirms the theory that woodlice were crawling across terrestrial environs in what is now Ireland during the Carboniferous period — and perhaps earlier.

Now that scientists know what these early woodlice cousins looked like, and what kinds of environments they inhabited, they’ll have a better idea of what to look for when examining more ancient deposits.

“Our work is an advance in the field of the evolution of invertebrate animals, especially crustaceans, and in our knowledge of the timing of their colonization of land,” Robin said.,50646003.html

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