Aquatic worms are gross enough. But ancient aquatic worms were infinitely more terrifying. Ovatiovermis cribratus, which was recently classified as a new species, is no exception. The worm, which lived about 500 million years ago, is like something out of H.R. Giger’s sketchbook.
Thankfully, it was only about as big as a thumb. But its appearance was fearsome. It looked a cross between a shrimp, a sea pig, a centipede and whatever your worst nightmare is. It was a genetic forebear of arthropods and tardigrades, which lived in shallow seas around North America.
Two Ovatiovermis fossils are known to science. The first of them was found many years ago and the second in 2011, a lucky find made by a tourist who was investigating the Burgess Shale.
Both of the fossils were found in the Burgess Shale Formation, a UNESCO World Heritage site that’s famous for yielding a bounty of marine fossils. It used to be an ancient seafloor. Now, it’s in the Rockies, in British Columbia.
Burgess Shale fossils are remarkable not only for their number, but also for their quality. They tend to preserve a large proportion of the original organisms’ soft tissue as well as their bones and chitinous exoskeletons. The Burgess Shale is about 508 million years old, making it one of the earliest fossil beds to preserve soft-part imprints.
A paleontologist named Charles Walcott discovered the Burgess Shale in 1909. He came back the next year with family in tow to build a quarry at Fossil Ridge. He kept coming back until 1924, collecting specimens along the way. By the end of his career, he had gathered over 65,000 fossils.
The worm’s name gives a clue as to it lifestyle. “Ovatiovermis” means that it stood upright on the seafloor, extending its upper body into the current. “Cribratus” refers to the way it likely collected food, by sieving it out of passing water.
Ovatiovermis cribratus belonged to the Lobopodian group of organisms.
According to Cédric Aria, who co-authored a study published recently about the newly discovered worms, “Lobopodians have mostly been seen so far as an eclectic group. We think that suspension feeding was common among them and turned out to be important in the initial ‘burst’ of that colossal group that gave rise to water bears, velvet worms and arthropods.”
The fossils were found in a deposit at the bottom of a 160-meter-tall cliff. The area would have been deeply enough submerged to not be disturbed by surface agitation and waves, even during storms. We used to believe that the Burgess Shale was deposited in “anoxic” conditions, meaning devoid of oxygen, but research now suggests that oxygen was cycled that deep regularly.
If the worm gives you the willies, don’t worry. They’re long extinct. But there are plenty of other creepy-crawlies out there that are just as weird or weirder.