Built-to-Last Beastie Gave Rise to Insects, Spiders and Shellfish

An otherworldly creature that lived a half billion years ago is helping scientists to recreate what the common ancestor of insects, spiders, scorpions and crustaceans looked like.

The bizarre animal, appropriately named Hallucigenia sparsa, suggests that the common ancestor of everything from black widow spiders to giant lobsters was far more complex than previously suspected. A common aspect of most of these animals, including spiders, is that they molt.

“It turns out that the ancestors of molting animals were much more anatomically advanced than we ever could have imagined,” co-author Jean-Bernard Caron, curator of invertebrate paleontology at the Royal Ontario Museum, said in a press release.

Caron added that Hallucigenia and its kind were “ring-like plate-bearing” species “with an armored throat and a mouth surrounded by spines.”

Hallucigenia was so bizarre that, for years, scientists couldn’t figure out which side of it was the front and which was the back. Some researchers even mistakenly drew the creature upside down.

“Prior to our study, there was still some uncertainty as to which end of the animal represented the head, and which the tail,” said co-author Martin Smith of Cambridge University’s Department of Earth Sciences.

He added, “A large balloon-like orb at one end of the specimen was originally thought to be the head, but we can now demonstrate that this actually wasn’t part of the body at all, but a dark stain representing decay fluids or gut contents that oozed out as the animal was flattened during burial.”

New fossils for its head, outlined in the latest issue of Nature, were unearthed in the Burgess Shale of Yoho National Park in western Canada. They reveal that Hallucigenia had a long head with a pair of simple eyes, which sat above a mouth that featured a ring of teeth-like needles. The latter were probably helped to generate suction, flexing in and out, like a valve or plunger, order to suck food into the organism’s throat.

The researchers speculate that the “needles” in the throat worked like a ratchet, keeping food from slipping out of the mouth each time it took another “suck” at its food. (Later animals, such as fish, evolved actual teeth as we know them, which permitted biting and chewing of food.)

Read more at Discovery News