Fossil may solve mystery of what one of the weirdest ever animals ate

Perhaps one of the strangest animals that ever lived was a scavenger. A re-examination of fossils first described in the 1970s appears to show a swarm of Hallucigenia feeding on the corpse of a comb jelly.

Hallucigenia was a small animal measuring up to 5 centimeters long. It had a worm-like body with several legs, as well as long, sharp spines on its back. Because of its peculiar appearance, paleontologists first reconstructed the animal upside down, assuming that the spines were legs.

It lived in deep waters during the Cambrian period (about 539 million to 487 million years ago), when many major animal groups emerged. Hallucigenia was first identified in rocks from the Burgess Shale deposits in British Columbia, Canada. It is related to velvet worms, tardigrades and arthropods (the group that includes insects and spiders).

Little is known about the lifestyle of this ancient animal. For example, none of the Hallucigenia The fossils found so far have preserved their gut contents, so we don’t know what they ate.

Javier Ortega-Hernández of Harvard University re-examined a fossil from the Burgess Shale that was used in the original description of Hallucigenia in 1977, but which has not been examined since.

It is the remains of a soft-bodied gelatinous organism, measuring 3.5 cm by 1.9 cm, which was severely damaged. Ortega-Hernández identified it as a comb jelly, or ctenophore.

Scattered on the comb jelly, Ortega-Hernández identified Hallucigenia thorns, representing seven individuals. It suggests that the comb jelly died and sank to the bottom of the sea, where the Hallucigenia swarmed on it and fed, probably by suction. While they were doing this, they were all buried in mud and eventually fossilized.

Ortega-Hernández declined to be interviewed by New scientist because the paper has not yet been peer-reviewed.

“I think this is a compelling ecological interaction,” says paleontologist Allison Daley of the University of Lausanne in Switzerland. She calls it a “snapshot,” representing “a moment in time that may have lasted only a few minutes or hours and happened to be captured in the fossil record.”

Hallucigenia It is known to have lived in deep water, Daley said, and nutrients are scarce in the deep. It makes sense that the species survived by quickly finding and eating rich food sources, like dead comb jelly. “Suction feeding would be very effective on such a soft animal,” she says.

Jean-Bernard Caron of the Royal Ontario Museum in Toronto is less convinced. Just because the Hallucigenia and ctenophore fossils are found together, he says, that doesn’t necessarily mean they interacted in real life. It could be that underwater mudslides transported them to the same resting place.

Because most of the known Hallucigenia the fossils are just thorns, Caron suggests an alternative interpretation: the animals could have molted, shedding their skin to grow.

Dinosaur hunting in the Gobi Desert, Mongolia

Embark on an exhilarating, one-of-a-kind expedition to discover dinosaur remains in the vast wilderness of the Gobi Desert, one of the most famous paleontological hotspots in the world.