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Face of Mysterious Sea Creature Hallucigenia

Scientists have finally made out what the strange tiny sea animal Hallucigenia which lived more than 500 million years ago looked like. The findings are published in the journal Nature.


The Hallucigenia‘s complete form

Until recently, the fossils of the Hallucigenia that were available were without heads. Consequently, scientists have been unable to generate a complete image of the organism. Now, specimens dug from a site in Canada known as the Burgess Shale revealed what researchers have been seeking since long: the missing head parts. Thus was exposed the face of the Hallucigenia.

Dr Martin Smith, from the University of Cambridge, said: “It looks completely surreal. It is like something from another world.”


The fossil dating back to the Cambrian period, more than 500 million years ago

Hallucigenia had aroused great curiosity and wonder ever since its first fossil was found over a century ago. The tiny creature, making less than 2 cm in length, and thinner than a human hair, revealed a strange appearance: huge spines occurring in pairs covered one side of its body while stick-like clawed appendages adhered to its other side. Scientists were initially confused as to its morphology. The incomplete fossils did not help either.

“It’s had a pretty chequered history,” said Dr Smith, one of the co-authors from the University of Toronto, Canada.

“When it was first formally described, it was the wrong way up. It was only recently that we found on which side were its feet and which side was its back.

“Even then there has still been a lot of ambiguity as to which end was the head and which end was the tail.”

Fortunately, new fossils unearthed from the Burgess Shale show the complete form of the creature. It was then discovered that its head was spoon-shaped with additional bizarre features; though previously, a “blob” observed on the fossils were mistaken for its head.

“When we put it into the electron microscope, we were delighted to see not just a tiny pair of eyes looking back at us, but also beneath them a really cheeky semi-circular smile.

“It was as if the fossil was grinning at us at the secrets it had been hiding,” affirmed Dr Smith.

Furthermore, its mouth revealed the presence of teeth, and a supplementary set of teeth emerging from its throat leading to its stomach. The scientists interpreted the presence of this feature as meaning that the creature might have used it to suck up food and pushed it down its alimentary canal.

The scientists also found out more about the strange blob that was thought to be its head in the past:-

“What our study shows is that it has a different composition from the animal. And rather than representing part of its body, it actually represents decay fluid – the contents of its guts – squeezed out as the animal was buried and fossilised,” said Dr Smith.

dark blob

Dark blob seen at the left.

Other researchers have spoken out about the potential of the findings. For instance, Dr Xiaoya Ma, from the Natural History Museum, commented on the results as follows:-

“Recently Hallucigenia sparsa was suggested to represent an early ancestor of the living velvet worms, known as Onychophora, as both of them share the similar growth pattern of claws.

“Velvet worms also possess a worm-like body with paired non-jointed legs, but they don’t have paired dorsal spines.

“The discoveries will improve our understanding of the early evolution along the evolutionary line leading to today’s velvet worms.”


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