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Mandibulates – the many-legged, plier-mouthed creatures that include ants, millipedes and prawns – are, far and away, the most diverse and numerous animals on the planet. Now a long-extinct example of a mandibulate, discovered more than a century ago, is finally getting a chance to help explain the group’s evolutionary success.

The Waptia fieldensis was among the first fossils unearthed by American paleontologist Charles Walcott in August of 1909.Royal Ontario Museum

Named Waptia fieldensis, after British Columbia’s Wapta Mountain, the thumb-sized animal was among the first fossils unearthed by American paleontologist Charles Walcott in August of 1909, when he explored the Burgess Shale, a 500-million-year-old rock formation in what is now Yoho National Park.

Despite its early discovery and relative abundance in the shale, the creature had not been thoroughly described until French and Canadian researchers examined more than 1,800 specimens of Waptia from collections at the Royal Ontario Museum in Toronto and the Smithsonian Institution in Washington. Their results, published Wednesday in the research journal Royal Society Open Science, amount to a definitive reconstruction of the long-vanished beast.

Waptia fossils are just a delight for the eyes and the mind and there is no getting tired of looking at them,” said Cédric Aria, a postdoctoral fellow at the Nanjing Institute of Geology and Palaeontology in China who participated in the project.

Among the new findings are a complex set of head appendages, related to feeding, which anticipate those found on insects and crustaceans. Together with other features, they suggest that Waptia branched off from a shared ancestor with those two modern groups, pushing some of their more sophisticated adaptations further back in time.

Previous work revealed that female members of the species kept their eggs hidden under their saddle-like carapaces, offering one of the earliest known examples of an animal protecting its young.

An illustration of Waptia fieldensis Illustration by Marianne Collins © Royal Ontario MuseumMarianne Collins/Royal Ontario Museum