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

The prehistoric animal is so bizarre that, for years, scientists couldn’t figure out which side of it was the front and which was the back.

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.

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"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.

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"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.)

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As if these features of the creature weren't unusual enough, it's also known that Hallucigenia had pairs of lengthy spines along its back and seven pairs of legs ending in claws. It also featured three pairs of tentacles along its neck.

Clearly this little beastie was formidable and built to last!

And it did for thousands of years, in its evolutionary place near the base of the family tree that includes insects, arachnids and crustaceans. With such an ancestor, it's little wonder that these creatures to this day, such as cockroaches and ants, are true survivors, becoming some of the most successful species on the planet.

Reconstruction of Hallucigenia sparsa.

Insects and other creepy crawlies may be tiny, but their lineages are mighty, finds a new study that determined the common ancestor of mites and insects existed about 570 million years ago. The study, published in the latest issue of the journal Science, presents an evolutionary timeline that settles many longstanding uncertainties about insects and related species. It found that true insects first emerged about 479 million years ago, long before dinosaurs first walked the Earth. Co-author Karl Kjer, a Rutgers entomologist, explained that mites are arthropods, a group that's distantly related to insects. Spiders and crustaceans are also arthropods.

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Spiders such as the huntsman spider can, like mites, trace their lineages back to about 570 million years ago, according to the new study. The researchers believe that the common ancestor of mites, spiders and insects was a water-dweller.

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Millipedes, such as the one shown here, as well as centipedes are known as myriapods. The most recent common ancestor of myriapods and crustaceans lived about 550 million years ago. Again, this "mother of many bugs" would have been a marine dweller. Kjer explained, "You can't really expect anything to live on land without plants, and plants and insects colonized land at about the same time, around 480 million years ago. So any date before that is a sea creature." Moving forward in time, the most common ancestor of millipedes and centipedes existed a little over 400 million years ago. The leggy body plan has proven to be extremely successful.

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"This is an early insect that evolved before insects had wings," Kjer said. Its ancestry goes back about 420 million years. The common ancestor of silverfish living today first emerged about 250 million years ago. Dinosaurs and the earliest mammals likely would have then seen silverfish very similar to the ones that are alive now.

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Dragonflies and damselflies have family histories that go back about 406 million years. Kjer said that such insects looked differently then, however. "For example," he said, "they had visible antennae." Their distant ancestors were among the first animals on earth to fly.

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"Parasitic lice are interesting, because they probably needed either feathers or fur," Kjer said. As a result, they are the relative newbies to this list. Nonetheless, the researchers believe it is possible that ancestors of today's lice were around 120 million years ago, possibly living off of dinosaurs and other creatures then.

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Crickets, katydids and grasshoppers had a common ancestor that lived just over 200 million years ago, and a stem lineage that goes back even further to 248 million years ago. A trivia question might be: Which came first, these insects or grass? The insects predate the grass that they now often thrive in.

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Dinosaur Era fossils sometimes include what researchers call "roachoids," or wing impressions that were made by ancestors to today's roaches, mantids (like the praying mantis) and termites. "Some cockroaches are actually more closely related to termites than they are to other cockroaches," Kjer said, explaining that this makes tracing back their lineages somewhat confusing. He and his colleagues determined that the stem lineage goes back about 230 million years, while the earliest actual cockroach first emerged around 170 million years ago.

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Termites and cockroaches have a tightly interwoven family history. Termites similar to the ones we know today were around 138 million years ago. Now we often think of termites as pests, but they are good eats for many different animals, which back in the day would have included our primate ancestors.

Flies like houseflies that often buzz around homes belong to the order Diptera, which has a family tree that goes back 243 million years ago. The most recent common ancestor for modern flies lived about 158 million years ago, according to the study. There is little doubt that the earliest humans, and their primate predecessors, had to contend with pesky flies and all of the other insects mentioned on this list. All of these organisms are extremely hardy. The researchers determined that, in the history of our planet, there has only been one mass extinction event that had much impact on insects. It occurred 252 million years ago (the Permian mass extinction), and even it set the stage for the emergence of flies, cockroaches, termites and numerous other creepy crawlies.

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