An international group of researchers has recently discovered the fossility of a species that has given rise to brahiodes, mshanks and tronidams; all three groups of marine beings that feed on water are attached to the seabed, but each group has highly specialized feeding structures, and they are very different.
Scientists reported in a new study that the fossil species, called Wufengella bengtoni, is a member of an older group of organisms with shells called tommotiides.
The find adds a new piece to the puzzle for scientists: how animals evolved during the Ambrian explosion, the time in the Kimbrian period, when early life on Earth quickly diversified.
The brahiopods are double-barreled creatures with shell; the mshanks have a soft body with tentacles, and the foronides are trapped in protective tubes made of chitin, a material that strengthens organic structures such as exoskelets, beaks, and shells.
Prior to W. Bengtsoni's discovery, the systemists assumed that the ancestors of all these groups of animals could be segmented worms, based on the similarities between the embryo development of groups in modern animals.
But while researchers had some idea of what this hypothetical ancestor might look like, they weren't sure they'd ever find him.
"One of the things we often mentioned when we were sitting in a pub and fantasizing about what we might hope to find once was this elusive tommotiid," co-author Jacob Winter, Associate Professor of Macroeconomic Evolution at Bristol University.
The fossil was found at the fossils of Chengjiang biota in the province of Yunnan in south-west China, a rare discovery because such animals are usually not well preserved so that paleontologists can study them in detail.
"They wandered through the reefs in the shallow tropical waters that existed then," Winter said.
In these ancient reef systems, dead animals were usually washed until their bodies fell apart, and their soft tissue was often deposited in oxygen - rich reefs before they could be sequestered.
"This particular animal, fortunately for us, was washed away in deep water, where it was buried in the ilyle, where it was preserved," Winter said.
Although researchers predicted the general appearance of W. Bengtsoni's body, some of the fossils became a big surprise, and he had the shutters on the body that could be used to suck the animal into the reef when the waves were there, suggested Winter.
This species also had long brushes on the sides that may have been used to detect mining or to protect against predators.
The authors of the study are not sure that the animal was eating, but his body was not equipped to filter water or to remain stationary, so they know that it was not a filter that was attached to the seabed as its descendants.
The researchers believe that this is an ancestor of brahiopod, mshank, and foronide because he had a common skeleton with these groups, and as life developed during the Bombing, animals filled different ecological niches and took different structures of the body.
"Sometimes the ancestors may be very different from their immediate surviving relatives," Winter said.
Martin Smith, an associate professor of paleontology at the University of Darham in England, who was not involved in the study, described the new study as an "unblemished example" of science. "This is a fantastic study," Smith said.
"We do see how these groups combine with each other and how they come from one common ancestor. This brings us up to the stage of an evolutionary tree," Smith added. "This is the next frontier, we go a little deeper than time, and we really begin to see the origin of the Ambrian explosion when all the complex plans of the body appear."