Modern annelids, such as earthworms and leeches, actually originated from a 2-centimeter worm with hundreds of hairlike bristles. They lived underwater more than 500 million years ago.
This groundbreaking discovery was made after a research team with the Royal Ontario Museum examined a perfectly preserved fossil of a 2-centimeter worm with hundreds of hairlike bristles.
The rare fossil is among the 20,000 animal remains that were recovered from the Burgess Shale at Kootenay National Park, British Columbia, in 2012, 2014, and 2016.
Such massive amount of evidence documents an underwater landslide that buried and killed prehistoric creatures, explains University of Toronto and ROM researcher Karma Nanglu.
Among those animals that were trapped on the seafloor, over 500 have been described as new species, including the small worm named Kootenayscolex barbarensis.
Prehistoric Worm: Kootenayscolex Barbarensis
Because of such rarity, the evolutionary history of many annelids is not well-documented due to the lack of evidence regarding their original appearance and how it changed over time.
"You need to look to truly exceptional fossil deposits like those found in the Burgess Shale to find well-preserved body fossils. Even then, they're quite uncommon and many of the currently described species there are still poorly understood," says Jean-Bernard Caron, senior curator of invertebrate paleontology at the ROM.
Upon examination, the recently discovered fossil was found to contain the soft tissue that makes up its body. This evidence gives scientists an understanding on how heads of segmented worms have evolved.
Shocking Discovery: Worm Fossil Shows Unique Features
Although similar fossils were found in Greenland, Nanglu claims that they are not as well-preserved as the one uncovered in Canada, where the animal's body is seen more clearly with a distinct head structure.
Additionally, attached to its head are two tubelike features called palps, which the species used to feel the ground they are moving on.
Scientists believe that when it was still alive during the Precambrian Era, it crawled on the ocean floor to feed on organic material. A report states that this function strongly ties it to today's earthworms and leeches with the same physical feature.
Furthermore, the worm's remains showed its bristles did not only cover its body. They extended to a part of its head, particularly on the area surrounding its mouth.
This paleontological discovery serves as a "powerful tool" in the investigation of modern animal diversity and unique morphologies.