Some truly scary creatures lurk within the ocean's depths. And that's been the case almost from the beginning. Around 508-million-years ago, one of the earliest predators to terrorize the seas was an armored creature called Habelia optata. It had five jaws, body armor and a jackknife on its head used for ripping open shells. Now, as Emily Chung at the CBC reports, paleontologists have taken a closer look at Habelia and found that it’s a close relative to modern insects and spiders, and can perhaps help scientists tease through their early evolution.

Habelia was first described over 100 years ago from fossils found in the Burgess Shale deposit in British Columbia. The creature looks truly fearsome, like a combination of the alien from Predator and an evil shrimp. “If you're looking for a scary Hollywood creature, it probably would be the perfect one,” says Cédric Aria, lead author of the study on the creature in BMC Evolutionary Biology, Chung reports. "It’s like a centipede or perhaps an insect that would have not one pair of mandibles, but five."

Though fearsome looking, these beasts were only about two centimeters long, or less than an inch. Its features, like a segmented body, exoskeleton and segmented limbs, put it squarely in the lineage of arthropods, which today includes insects, scorpions, spiders and lobsters. But researchers weren’t sure how to further classify the creatures, according to a press release.

That’s why researchers from the University of Toronto and Royal Ontario Museum took a closer look at Habelia’s anatomy. What they found is that Habelia is a close relative of the ancestor of chelicerates—a subdivision of arthropods which includes spiders, scorpions, horseshoe crabs and mites.

“Habelia now shows in great detail the body architecture from which chelicerates emerged, which allows us to solve some long-standing questions,” says Aria, who is currently a post-doc at the Nanjing Institute of Geology and Palaeontology, in the press release. “We can now explain why, for instance, horseshoe crabs have a reduced pair of limbs—the chilaria—at the back of their heads. Those are relics of fully formed appendages, as chelicerates seem to originally have had heads with no less than seven pairs of limbs.”



The researchers looked at 41 specimens of Habelia for their study, carefully measuring the fossils to come up with 3D renderings of the creature, which helped unlock some secrets. For instance, an appendage on its head used in modern arthropods for walking, was used by Habelia for crushing things, Chung writes. It also had five pairs of legs attached to its thorax used for walking. Modern spiders and scorpions have no legs on their thorax. And specialized mandibles in the face may have been used in the way antenna are used in modern insects.

In fact, Aria says that despite being 508 million years old, the little creature is quite sophisticated. “It's more complex than a lot of chelicerates that live today,” he says.

All that firepower packed onto its little head allowed it to rip apart baby trilobites. “This complex apparatus of appendages and jaws made Habelia an exceptionally fierce predator for its size,” Aria says in the release. “It was likely both very mobile and efficient in tearing apart its preys.”

That little trick of eating things with shells also reinforces how important the explosion of shelled animals—like trilobites—was at the time, known as the Cambrian explosion. An “arms race” of sorts developed between predators and prey leading to important evolutionary developments like compound eyes.

Habelia is just one of many incredible finds researchers have uncovered in the Burgess shale. As Siobhan Roberts wrote for Smithsonian Magazine in 2009, "the Burgess Shale is Mecca for paleontologists." It was discovered in 1909 by Charles Doolittle Walcott, the fourth Secretary of the Smithsonian Institution, and captures a stunning diversity of life during the Cambrian explosion, when the variety of creatures suddenly took off.

Many of the animals found in the Burgess shale are the ancient relatives to critters that still walk, swim and fly around the planet today. And though many puzzles still remain about this time of Earth's history, by studying amazing specimens like Habelia, researchers can both learn more about ancient and modern creatures alike.