Hallucigenia
It sucked and devoured dead bodies at the bottom of the sea. New analysis is of the same fossil around 500 million years old found in 1977.
A marine fossil around 500 million years old could reveal what one of the most enigmatic animals of the Cambrian period ate.
The specimen, described in a study in bioRxiv, suggests that these small organisms, often considered among the most “strange” ever found, could feed on dead soft-bodied animals at the bottom of the ocean, in behavior similar to scavenging behavior.
Hallucigenia It measured around 5 centimeters and lived in deep waters at a crucial stage in the evolution of animals. It had an elongated body, similar to that of a worm, with several extremities and a set of long dorsal spines, the most striking feature of its anatomy.
For decades, this set of features confused researchers, recalls: the first reconstructions interpreted the spines as if they were legs. Only with subsequent advances in paleontology was the idea that it was evolutionarily related to the “velvet worms” (onychophora), tardigrades and arthropods, although their ecology and way of life remained unclear.
The new analysis focuses on a fossil from the Burgess Shale, in Canada. According to the authors, this is the same specimen used in the original description of Hallucigenia in 1977, but which has not been re-examined in detail since then.
Or paleontologist Javier Ortega-Hernándezfrom Harvard University, identified very degraded traces of a gelatinous organism measuring around 3.5 centimeters in the rock block, interpreted as a ctenophore, a soft-bodied marine animal, sometimes compared to a “comb jellyfish”. Spines attributed to Hallucigenia appear on this body, belonging to at least seven individuals.
The proposed interpretation is that of a possible feeding “scene”: the ctenophore would have died and sunk to the seabed, attracting several Hallucigenia which would have grouped together to consume the soft body, possibly using a suction. For paleontologist Allison Daley, from the University of Lausanne, the fossil represents a “captured instant” in the geological record, preserving a rare interaction.
Not everyone agrees with the reading. Jean-Bernard Caron, from the Royal Ontario Museum, warns that geological processes can sometimes bring together the remains of different organisms without there having been a direct interaction.
The first fossils of the animal were discovered more than 100 years ago, but they were always incomplete, without the creature’s head. “Your appearance is totally surreal. It’s like I came from another planet“, said Martin Smith, researcher at the University of Cambridge and co-responsible for investigating the creature in 2015.
