Scientists Find the Head of 500 Million Year Old Hallucigenia Worm

Scientists Were Baffled For Years

Researchers, according to a paper in the journal Nature, have finally discovered which end of a mysterious worm fossil was, in fact, its head. Scientists had been studying these Hallucigenia fossils for decades after their initial discovery in the 1970s, never one hundred percent sure which end was the head and which end was the tail. In fact, the original theories about what the head was turned out to not even be a part of the Hallucigenia’s body!

How Did They Figure It Out?

The study was done by the Royal Ontario Museum in Canada and the Smithsonian. Researchers worked tirelessly to remove the immense amount of sediment that tends to get attached to 500 million year old fossils, using a micro-engraving tool to chip away at multiple Hallucigenia fossils. This allowed for a much closer examination of the Hallucigenia in the hopes of finding a clear giveaway, particularly eyes.

What Does It Look Like?

The scientists did, in fact, find the Hallucigenia’s eyes, allowing them to definitively state which side was the head and which was the tail. But their excitement didn’t stop at just the eyes; scientists were astonished by the worm’s mouth, with one of them even referring to it as a grin. The opening of the mouth was circular, and lined with teeth. Teeth also lined the throat, although these teeth were more needle-like in nature. The throat teeth are theorized to have been there to help grip food and send it further down, possibly by generating suction. There’s still no evidence, however, of what the food was that the teeth were gripping. Upon further inspection, there was also another error scientists had initially made besides the head; this Hallucigenia (more specifically named the Hallucigenia sparsa) had a number of spines sticking out of its back. However, scientists actually thought they were legs at first! This is more than likely due to the Hallucigenia’s legs being hidden in rock. Once the sediment was stripped away, the legs became apparent. Thanks to these new discoveries, some are even beginning to create the first drawings of what the Hallucigenia sparsa potentially looked like.



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