A new study has established the first-ever evolutionary history of all living millipedes, one of the planet’s first land animals that pioneered its terrestrial ecosystems (as the first chemical weapon manufacturers, too).

At a time when the Earth was bare, when there were no vertebrates, no trees, no leaves, no flowering plants, and no plants with seeds, millipedes were feeding on decaying mosses, decomposed slime, and primordial gunk.

Though that sounds unappetizing, someone had to complete the “dirty work” necessary to pave the way for life. Though they perform an essential function as one of the first animals on Earth, science still hadn’t fully tracked their history until now.

A new, groundbreaking study published in Current Biology addressed a 100-year-old gap in millipede science surrounding two rare groups of millipedes: Siphoniulida and Siphonocryptida.

Scientists knew that they existed, but without specimens for DNA analysis, they couldn’t confirm where they belonged in the millipede family tree.

But it was no easy feat to find them. One group spends its life underground, while the other survives in only a few known locations.

Penetrating 260 million years of history

Researchers traveled to Los Tuxtlas, Mexico, and Spain’s Canary Islands to collect Siphoniulus neotropicus and Hirudicryptus canariensis, two millipedes whose DNA had never before been included in an evolutionary analysis.

“It took 10 people over a week to find one tiny 10-millimeter adult,” said Luisa “Fernanda” Vasquez-Valverde, the paper’s first author, in a press release.

“Finding them in the field was hard because we were just seeing this little white nematode. We didn’t know for sure it was a millipede until we looked under the microscope.” 

After sequencing their DNA, comparing hundreds of genes across 82 millipede species, and combining those results with evidence from 29 fossils, researchers determined where the groups belonged in millipede history and when their lineages emerged.

“Millipedes may have originated nearly 460 million years ago — roughly 35 million years before the oldest known millipede fossils and much earlier than previously believed,” according to the press release.

Siphonocryptida turned out not to be a distinct order after all, but part of an existing lineage. Siphoniulida was finally placed among its closest relatives on the millipede evolution timeline.

All in all, the analysis of the millipede species revealed that the ancient animals originated 460 million years ago, roughly 35 million years before the oldest known millipede fossils, which was “the biggest surprise” to researchers —

“Just how ancient these lineages turned out to be.”

The completed family tree also revealed one of the millipedes’ most important adaptations: they made the first chemical weapons. And it was these defenses that helped scientists trace their origins to about 260 million years ago.

Although the new study brought new insights into one of the planet’s most significant animals, millipedes still hold secrets waiting to be discovered.

Still more to discover

Scientists have described more than 14,000 species worldwide, but experts believe that tens of thousands may still be out there undiscovered.

These “unheralded heroes of the ecosystem” may be one of nature’s most important detritivores — because they break down decaying plant material and return nutrients to ecosystems — but scientists still haven’t fully penetrated this lineage, which is more ancient than the dinosaurs and paved the way on land for vertebrates.

“It’s really kind of puzzling that they have such an important function in the ecosystem, and yet they’re so poorly known,” noted Paul Marek, the study’s lead investigator and associate professor in the College of Agriculture and Life Sciences’ Department of Entomology.

“Millipedes beat vertebrates onto land by more than 80 million years,” continued Marek. “They really set the stage for later life on land, including humans and vertebrates.”  

“There is all this potential for discovery,” a press release concluded. “It keeps me wondering what else we’re going to find.” 

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