Over a century ago, alien-looking fossils were unearthed in China, and their figure-eight anatomy was so strange, researchers have long puzzled over where they fit on the tree of life. Were they bivalved arthropods like trilobites or soft-bodied, water-filled sacs? Now, a team examining newly discovered, 500-million-year-old fossils belonging to this bizarre group reveal that they’re actually blind water creatures with backbone-like structures -- making them close relatives to vertebrates and our distant cousins.
Though they were first discovered in 1911, it wasn’t until 1997 when the fossils were described and given a name: vetulicolians. These hourglass-shaped marine filter-feeders were about 15 centimeters long and swam the seas during the Cambrian. They’ve since been discovered all over: Canada, Greenland, China and Australia.
Now, a team led by Diego García-Bellido from the University of Adelaide and John Paterson from the University of New England examined novel anatomical details preserved in a set of new vetulicolian fossils discovered in coastal cliffs on Kangaroo Island off the coast of South Australia. These vetulicolians have a long tail that’s supported by a stiff rod resembling a notochord -- a backbone precursor that’s unique to vertebrates.
The team believe they’re one of the first representatives of our vertebrate cousins, and they're closely allied to a group called tunicates, which include sea squirts and salps. All tunicates and humans alike belong to the same phylum, Chordata.
"They were simple yet successful creatures, large in number and in distribution across the globe,” Garcia-Bellido says in a news release. "Although not directly related to humans in the evolutionary line, we can confirm that these ancient water creatures are among our distant cousins.”
“Some of our stranger distant cousins,” Paterson adds in a university statement. These Kangaroo Island fossils warranted a new species, and the team named it Nesonektris aldridgei. “Nesonektris” is Greek for "island swimmer” and the species name honors Dick Aldridge, one of the pioneering vetulicolian researchers.
The findings were published in BMC Evolution earlier this month.
Images: University of Adelaide/South Australian Museum (middle)