by An armored “worm” that crossed ocean reefs 518 million years ago is the ancestor of three groups of aquatic animals that today live very different lifestyles and offers new clues about the explosion of different species at that time, according to a new study.
An international team of researchers recently discovered the fossil of a species that gave rise to brachiopods, bryozoans and phoronids. These three groups of filter-feeding sea creatures all cling to the sea floor, but each group has highly specialized feeding structures and looks very different from one another.
The fossil species, was named Wufengella bengtsoniis a member of an older, shelled group of organisms called tommotiids, scientists reported in a new study.
The finding adds a new piece to the puzzle of how animals evolved during the Cambrian explosion, a time during the Cambrian period (541 million to 485.4 million years ago) when early life diversified rapidly on Earth, introducing and establishing a variety of different body designs that we still see today in living animals.
Brachiopods are shelled, bivalve creatures. Bryozoans have soft bodies with crowns of tentacles, and phoronids are encased in protective tubes made of chitin, a material that strengthens organic structures such as exoskeletons, beaks, and shells.
Before its discovery W. bengtsonitaxonomists had hypothesized that the ancestor of all these animal groups might have been a segmented tommotiid worm, based on similarities in the embryonic development of the groups in living animals.
But while the researchers had some idea of what this hypothetical ancestor might look like, they weren’t sure if they would ever find it.
“One of the things we often mentioned when we were sitting in the pub imagining what we might hope to find one day was this elusive tommotiid,” co-author Jakob Vinther, associate professor of macroevolution at the University of Bristol. in England, he told Live Science.
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The fossil was found at the Chengjiang Biota fossil site in Yunnan, a province in southwest China. It’s a rare find because animals like this aren’t usually preserved well enough for paleontologists to study in detail.
“They were perching on reefs in the shallow tropical waters that existed then,” Winter said.
In these ancient reef systems, dead animals usually washed up until their bodies decomposed, and their soft tissues often decomposed in the oxygen-rich reef waters before fossilization took place.
“This particular animal, fortunately for us, washed up in deep water where it was buried in the mud where it was preserved,” Winter said.
While the researchers predicted W. bengtsoniIts general body design, some features in the fossil were a big surprise. It had fins on its body that could have been used for suction purposes, to anchor the animal to the reef when there were waves, Vinther speculated.
The species also had long hairs on its flanks that may have been used to detect prey or as protection from predators.
The study authors aren’t sure what the animal was eating, but its body wasn’t adapted to filter water or stand still, so they know it wasn’t a filter feeder that attached itself to the sea floor like its descendants.
Researchers are confident that it is the ancestor of brachiopods, bryozoans and phoronids because it shares a similar skeleton with those groups. As life evolved in the Cambrian explosion, animals filled different ecological niches and adopted different body designs.
“Sometimes ancestors can look very, very different from their closest living relatives,” Winter said.
Martin Smith, associate professor of palaeontology at Durham University in England, who was not involved in the study, described the new research as a “perfectly executed” example of science. “It’s a fantastic study,” Smith said.
“We’re really seeing how these groups fit together and how they evolved from a single common ancestor. It gives us a rung up the evolutionary tree,” Smith added.
“It’s the next frontier, we go a little deeper in time and really start to see the origins of the Cambrian explosion when all the complex body patterns appear.”
The study was published online Sept. 27 in the journal Current Biology.
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This article was originally published by Live Science. Read the original article here.
