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Hallucigenia finally finds a home

This is a reconstruction of the Burgess Shale animal Hallucigenia sparsa.
This is a reconstruction of the Burgess Shale animal Hallucigenia sparsa.
Credit: Elyssa Rider

Hallucigenia sparsa, one of the rarest and most controversial animals that emerged from the Cambrian Explosion, has finally been definitely classified and accounted for as an ancestor of modern velvet worms. Dr. Martin Smith of the University of Cambridge Department of Earth Sciences and colleagues made the defining discovery. The research was published in the Aug. 17, 2014, issue of the journal Nature.

The first known example of Hallucigenia was discovered in 1911 by Charles Doolittle Walcott in the Burgess Shale of Canada. To date 109 specimens of Hallucigenia have been discovered. The name Hallucigenia comes from the Latin hallucination meaning wandering of the mind in reference to the bizarre appearance of the animal and sparsa is Latin for rare or scattered referencing the rarity of the original find. The animals occupied the ocean floor about 505 million years ago.

Each specimen of Hallucigenia that has been found gives the appearance of a worm with legs. The animal had a series of paired spines on its back and seven pairs of legs that ended in a claw. The animals were a mere five to 35 millimeters in length. The size added to the confusion about their place in the history of animals.

The claws on Hallucigenia’s feet held the final clue that solved a 100-year-old mystery. The claws of Hallucigenia have the same chemical structure as velvet worms, also known as onychophorans, and the same laminar arrangement of layers of cuticle in the claw as velvet worms. The researchers claim that this is the defining evidence that places one of the oddest looking creatures that ever existed in the onychophoran phylum.

The study emphasizes that evolution is not always logical. The gene studies that produced the relationship between Hallucigenia and velvet worms also found that arthropods (spiders, lobsters, etc.) are related to velvet worms. The study changes all present relations between Cambrian creatures and living insects.