Hallucigenia's a Worm, Not a Drug – And No Longer Faceless

Hallucigenia isn't a drug like LSD. It's a worm which scientists believe is a common ancestor of all arthropods from shrimps to spiders, and it's becoming less of a mystery now that scientists got their first look at its face.

Scientists believe that the Hallucigenia emerged from the Cambrian Explosion some 500 million years ago with features similar to those of the modern velvet worm, according to the Washington Post.



British paleontologist Simon Conway-Morris first discovered the Hallucigenia fossil in 1977 in Canada's well-known Burgess Shale fossil field, according to National Geographic. The fossil had long tubular body, from one to five centimeters long with seven pairs of long spines stuck out in one direction and seven pairs of tentacles stuck out in the other.

No one knew what the head of the Hallucigenia looked like until researchers Martin Smith and Jean-Bernard Caron examined new well-preserved specimens and then re-analyzed the existing ones with the latest microscopes. Their study was published on Wednesday in the scientific journal Nature.

"It was about time we took some modern techniques to see what secrets it had," Smith told National Geographic, adding its features "really pop out under an electron microscope."

The researchers discovered the Hallucigenia had two simple eyes as compared to compound eyes of insects and had a mouth with needle-like teeth.

"When it was formally described originally, it was actually upside down, with the spikes being mistaken for legs and the legs being mistaken for tentacles on the back," Smith told the Post. "Even once we got the right way up, there was a lot of uncertainty about which end was the head and which was the tail."

Caron, curator of Invertebrate Palaeontology at the Royal Ontario Museum, said the Hallucigenia's teeth appeared to look like those seen in early moulting animals, suggesting they may have also had a tooth-lined throat.

"So where previously there was little reason to think that arthropod mouths had much in common with the mouths of animals such as penis worms, the Hallucigenia tells us that arthropods and velvet worms did ancestrally have round-the-mouth plates and down-the-throat teeth – they just lost or simplified them later," Caron noted.

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