Last Updated on May 7, 2026 by Staff
Scientists found a fossil in Wisconsin that changes what researchers know about the evolution of centipedes and millipedes. The identified species, named Waukartus muscularis lived around 437 million years ago. It may be one of the known relatives of modern myriapods before they fully adapted to life on land.
The study, published in Proceedings of the Royal Society B: Biological Sciences challenges a standing theory about how many-legged arthropods evolved. Researchers found that this ancient marine creature already had the type of unbranched legs seen in modern land-dwelling myriapods.
The discovery suggests that these specialized limbs evolved before arthropods moved onto land. It did not evolve as an adaptation to terrestrial life as scientists previously believed.
Ancient Fossils Found in Wisconsin
The fossils were discovered in the Silurian Brandon Bridge Formation in Waukesha, Wisconsin. This fossil-rich site, known as the Waukesha Lagerstätte is famous for preserving bodied marine organisms from the ancient Silurian period.
Researchers uncovered 35 fossil specimens of Waukartus muscularis. Many of them were exceptionally preserved. Some fossils retained evidence of muscle tissue, internal skeletal structures and delicate body parts.
The creature had a segmented body with numerous pairs of legs. It resembled centipedes and millipedes. Scientists noted that no fossil specimen showed more than 11 body segments.
This suggests the animal had an elongated body structure similar to its modern relatives. The fossils also revealed appendages near the head region. Researchers believe these may have been used for sensing the environment or feeding.
A Missing Evolutionary Link
For decades scientists have struggled to understand how Myriapods evolved. They also wanted to know when their distinctive body plan first appeared.
By analyzing the anatomy of Waukartus muscularis researchers determined that the species belongs outside the crown group of modern Myriapods. It is in the family tree. This places it very close to the branch that eventually gave rise to centipedes and millipedes.
The team also compared Waukartus with another arthropod group called euthycarcinoids. Earlier studies identified them as relatives of Myriapods.
Together these findings suggest that several important features associated with land life may have evolved while these creatures were still living in environments.
Legs Built Before Land
One of the surprising discoveries involved the structure of the animal’s limbs. Most aquatic arthropods possess appendages with an extra outer limb segment.
However Waukartus lacked these limbs. Instead it possessed appendages. Each leg consisted of a branch only.
Today modern Myriapods, insects and arachnids also possess limbs. Scientists had long assumed that losing the branch was an adaptation that helped arthropods walk efficiently on land.
A Window Into Early Evolution
The discovery of Waukartus muscularis fills a gap in the evolutionary history of arthropods. It provides insight into how early body structures developed before the rise of fully terrestrial ecosystems.
Researchers say the fossil also highlights the importance of fossil sites like the Waukesha Lagerstätte. Delicate ancient organisms can survive for hundreds of millions of years.
Beyond helping scientists understand centipedes and millipedes the discovery may also improve knowledge of how major evolutionary transitions occur. The movement from sea to land was one of the most important events in Earth’s history. The study demonstrates that some biological innovations may appear long before they become truly useful. In the case of Waukartus, the legs that would later help its descendants thrive on land may have first evolved while walking across the sea floor.