An ancient armored worm may hold the key to unraveling the evolutionary history of a diverse collection of marine invertebrates.
Discovered in China, an approximately 520-million-year-old fossil of the newly identified worm, nicknamed wufengellait could be the missing link between three of the phyla that make up a cadre of sea creatures called lophophorates.
From a genetic analysis, wufengella is probably the common ancestor connecting brachiopods, bryozoans, and phoronid worms, paleontologist Jakob Vinther and colleagues report September 27 in current biology.
“We had been speculating that [the common ancestor] it could have been some wormy animal that had plates on its back,” says Vinther, of the University of Bristol in England. “But we never had the animal.”
Roughly half a billion years ago, nearly every major animal group burst onto the scene in a flurry of evolutionary diversification during what is known as the cambrian explosion (Serial number: 04/24/19). During this time, the lophophorates experienced rapid species growth, which obscured the evolutionary history of the group.
One thing that unites the different phyla in the group is their tentacle-like feeding tubes known as lophophores. But beyond that similarity, the blades are all quite different. Brachiopods are shelled animals that at first glance look like clams. Bryozoans, commonly known as moss animals, are microscopic sedentary creatures that live in coral-like colonies. And phoronids, or horseshoe worms, are soft-bodied, unsegmented creatures that live in stationary, tube-shaped structures. (More recently, some researchers have determined that hyoliths — an extinct animal known for its conical shells (Serial number: 01/11/17) — are also lophophorous due to the tentacled organ that surrounds their mouth.)
wufengella it does not belong to either of these phyla, Vinther and colleagues found. But the creature has characteristics similar to those of brachiopods, horseshoe worms, or bryozoans: a series of asymmetrical armored dorsal plates, a worm-like body, and bristles protruding from lobes that surround its body.
The fossil is a “great find,” says Gonzalo Giribet, an invertebrate zoologist at Harvard University who was not involved in the research. Still, the scientists’ analysis does not confirm that wufengella it is the long-sought missing link, he warns, but rather suggests it.
Some researchers had hypothesized that the lophophorates’ common ancestor would be a stationary creature that sat on the seafloor and fed only through tubes, similar to its modern relatives. the wufengella fossil could refute this idea; the animal’s body plan suggests instead that it was crawling, the researchers say.
a fossil like wufengella it had long been high on the list of Vinther fossils that he and his colleagues hoped to find. But “we always thought, ‘Well, we’ll probably never see that in real life,’” he says. Typically, such a creature would have spent its life in shallow water. Organisms don’t tend to do well there, they decompose faster due to exposure to a lot of oxygen. Vinther suggests that the wufengella which his team likely found washed up in deep water in a storm.
Now that researchers have found one wufengella, they hope to find more, in part to see if there are other varieties. And perhaps the team could identify even more distant ancestors further back in the tree of life that could connect lophophorates to other groups of animals like mollusks, says Vinther, further explaining how life on Earth is connected.