Researchers from Virginia Tech were able to unearth fossils of ancient microscopic worms believed to have existed some 530 million years ago. The discovery, which was made in South China, is said to fill in the gaps between what remains unknown of kinorhyncha (kino) worms or mud dragons.
Scientifically known as Eokinorhynchus rarus (E. rarus), the species are invertebrate animals that date back from the Cambrian period. The species are related to arthropods such as shrimps and insects because both share the same exoskeleton and segmented bodies, but not jointed legs.
Although the worm fossils date back to millions of years ago, kinorhyncha specimens have never been reported in the past. With this, the researchers said their discovery can help reveal undocumented evolutionary history.
"Our discovery is the first report of kino fossils," said study lead author Shuhai Xiao.
In 2013, the first fossil was discovered in Nanjing, China by Huaqiao Zhang. More specimens were unearthed during the latter part of that year and in 2014. The first fossil measured 0.078 inches long and 10.02 inches wide.
When Xiao received an image of the specimen, he knew right then what it was.
"I immediately recognized it as something very similar to modern kinos," he said.
The team used electron microscopy to comprehensively form images of the fossils' surface. For the internal parts and midguts, the team used microCT. The data the team was able to produce was so extensive that it most likely entailed everything there is to know about the morphology of the fossils.
The mystery behind how and why body segmentation in different animal species changed through time may also be explained by the fossils.
As the investigations continued, the scientists found more and more similarities between E. rarus and living kinorhynchas, strongly backing up a possible evolutionary relationship.
Among the likeness discovered between the ancient and modern species include having five hollow spines arranged bilaterally and exuding body segments with articulated plates. The number of segments, however, is higher in the ancient species, suggesting ancestorship.
The full study was published in the Nature's Scientific Reports.