Millions of years before dinosaurs appeared and long before vertebrates walked the land, millipedes were already thriving on the Earth’s surface.
These humble decomposers played important roles in some of the planet’s earliest terrestrial ecosystems. Yet despite their remarkable history, key questions about their evolution remain unanswered.
Now, an international team led by Virginia Tech researchers has filled in one of the last gaps in the millipede family tree, shedding new light on the ancient creatures that helped prepare Earth for life on land.
The study, published in current biologyPresents the first complete evolutionary history of all living millipede orders. By combining DNA data from modern species with physical evidence preserved in fossils, researchers traced the origin of millipedes to about 460 million years ago, suggesting they existed long before the oldest millipede fossils ever discovered.
“Millipedes have dominated vertebrates on land for more than 80 million years,” said Paul Marek, the study’s principal investigator and associate professor in the Department of Entomology in the College of Agriculture and Life Sciences. “They really set the stage for later life on land, including humans and vertebrates.”
Solving a long-standing centipede mystery
For more than 100 years, scientists have recognized the existence of two rare millipede groups, Siphonulida and Siphonocryptida. However, because fresh samples were not available for DNA analysis, researchers could not determine where these groups belonged on the millipede family tree.
One group consists of centipedes less than a centimeter long that spend their lives underground. The latter survives only in a few known locations.
“These last two were like our white whales,” Marek said.
To find them, researchers traveled to Los Tuxtlas, Mexico, and the Canary Islands, Spain. there he collected Siphoniulus neotropicus And Hirudicryptus canariensisTwo species whose DNA had never before been included in any evolutionary study.
Luisa “Fernanda” Vasquez-Valverde MS ’21, Ph.D. Said, “It took 10 people more than a week to find this one tiny 10-millimeter adult.” ’24, first author of the paper and an assistant in Marek’s laboratory. “They were hard to find in the field 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.”
The team sequenced the DNA of both groups and compared hundreds of genes across 82 millipede species. They also included evidence of 29 fossils. Together, these data allowed researchers to determine where the mysterious groups fit within millipede evolution and when their lineages first emerged.
The project produced terabytes of genetic data and relied on Virginia Tech’s advanced research computing resources to reconstruct evolutionary relationships spanning hundreds of millions of years.
The results revealed that Siphonocryptida is not a separate millipede order as previously thought, but rather belongs to an existing lineage. Meanwhile, Siphonulida was eventually placed alongside its closest evolutionary relatives.
centipede on ancient earth
The analysis indicates that millipedes may have originated about 460 million years ago, about 35 million years earlier than the oldest known millipede fossils and much earlier than previous estimates suggested.
“The biggest surprise was how ancient some of these lineages were,” Marek said.
At that time the Earth looked very different from today. According to Marek, millipedes were among the earliest pioneers of life on land, helping to recycle nutrients by eating decaying organic matter in some of the first terrestrial ecosystems.
“There were no vertebrates, no trees, no leaves, no flowering plants, no seed plants,” Marek said. “Millipedes were feeding on decaying moss, decomposed mud and primordial dirt on the Earth’s surface.”
Origin of millipede chemical defenses
The newly completed evolutionary tree also helped researchers figure out when one of the group’s most remarkable adaptations appeared.
“They created the first chemical weapon,” Marek said. “They’re little chemical factories.”
The study shows that these chemical defenses originated about 260 million years ago, providing the clearest evidence yet of when millipedes first evolved this ability.
Unsung Ecosystem Engineers
Today, centipedes remain one of the world’s most important pests. By breaking down dead plant material, they help recycle nutrients and support healthy ecosystems.
“It’s really surprising that they have such an important function in the ecosystem, and yet they are so little known,” Marek said.
Even with more than 14,000 described species worldwide, researchers believe there may still be thousands of millipede species undiscovered. Marek and his students have found new species in locations ranging from Virginia Tech’s Blacksburg campus to Los Angeles.
For scientists like Vasquez-Valverde, the spirit of exploration is part of the appeal.
“There’s a lot of potential for discovery there,” he said. “It makes me wonder what else we’re going to discover.”
The research was funded by the National Science Foundation and included scientists from the Field Museum of Natural History, Hampden-Sydney College, Universidad de La Laguna, Virginia Tech School of Plant and Environmental Sciences, Australian National Insect Collection, West Virginia University and Universidad Autónoma del Estado de Hidalgo.