This shelled worm is a tomot crustacean called Wufengella bengtsoni.
A new study found that 518 million years ago, a bristle-worn "worm" crossed the ocean reefs and was the ancestor of three aquatic animals. Today, the three animals have very different lifestyles, which provide new clues for the outbreak of diverse species at that time.
An international research team recently discovered fossils of a species that originated from brachiopods, bryozoans and dragonflies; these three groups of filter feeding marine organisms all fix themselves on the seabed, but each group has a highly specialized predation structure, which looks very different. The fossil species, called Wufengella bengtsoni, is a member of the older shelled biota Tomot crustacean, scientists report in a new study.
This discovery adds new clues to the puzzle of how animals evolved during the "Cambrian explosion". Cambrian period (541 million to 485.4 million years ago), early life on Earth rapidly diversified, introducing and establishing various body structures that we can still see in living animals today.
Brachiopod is a shelled bivalve; bryozoan is a mollusk with a tentacle crown, and the wingworm is wrapped in a protective tube made of chitin , a material that enhances organic structures such as exoskeleton, beak and shell. Prior to the discovery of W. bengtoni, taxonomists speculated that the ancestors of all these animal groups might be a subdivided worm-like tomotel shellacea based on similarities in the development of existing animals. But while researchers have some understanding of what the hypothetical ancestor might look like, they are not sure if they can find it.
This fossil was discovered at the Chengjiang Biota fossil site in Yunnan Province in southwestern China. This is a rare discovery because animals like this are usually not well preserved enough that paleontologists cannot study them in detail.
They shuttled through the coral reefs in the shallow tropical waters that existed at the time. In these ancient reef systems, dead animals are usually washed away until their bodies break down, and their soft tissues usually rot in the oxygen-rich water of the reef before petrification occurs. Fortunately, this special animal was washed into deep water, buried in the mud, and preserved.
Although researchers predicted the overall body structure of W. bengtoni, some of the characteristics on the fossils were still surprising. It has flaps on its body that can be used to suction, fixing the animal to the reef when there are waves. The species also has long bristles on both sides of the body, which may be used to sense prey or to protect itself from predators. The authors of the study weren't sure what the animal had, but its body wasn't used to filter water or stay still, so they knew it wasn't a filter feeder attached to the seabed like its offspring.
Researchers are convinced that it is the ancestor of brachiopods , bryozoos and terror because it has a similar skeleton to these groups. As life evolved during the Cambrian explosion, animals occupied different ecological niches and adopted different body structures. Sometimes, ancestors may look completely different from their closest relatives.
"We are looking at how these groups come together and how they evolved from a common ancestor. This puts us on another step in the evolutionary tree," the researchers said. "This is the next frontier, we'll go deeper into the deeper time, and when all the complex body planes appear, we really start to see the origins of the Cambrian explosion."
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