500 Million Year Old ‘Alien Fish Taco’ Was One of the First Creatures with Jaws
Bizarre fossils of Cambrian creatures like the “alien fish taco” shed light on how a single group of jawed creatures came to account for about 90 percent of all animal species on Earth.
Reconstructing your life OdaraiaIt may have used small spines to carry food to its mouth, but researchers aren’t sure what the three-pronged teeth in its mouth were used for.
Illustration by Daniel Dufour. Courtesy of the Royal Ontario Museum
About 500 million years ago, a strange creature with bulging eyes, a rudder-like tail, and 30 pairs of spiny limbs extending from a cigar-sized body swam Earth’s oceans. Most of its legs were hidden inside a protective shell that encased almost its entire torso, preventing it from reaching the ocean floor. And like a little King Neptune, it had mysterious trident-like teeth between the jaw-like exterior structures at the front of its mouth.
It looked like an alien fish taco, but it was Odaraia ArataThe roughly 20-centimetre-long creature was likely buried under a thick layer of sediment and died a sudden death, but the circumstances that sealed the animal’s demise have immortalised it in the fossil record.
Paleontologists discovered the fossilized remains of these creatures in 1912 at the now-famous Burgess Shale site in the Canadian Rocky Mountains. Odaraia The fossil was examined again in the 1970s and 1980s, but the specimen was kept in storage at the Royal Ontario Museum in Toronto for several decades.
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Scientists are now using better tools and more modern techniques to pore over the remarkably preserved jaw fossil, and they’re particularly interested in its connection to the Cambrian explosion, a huge number of more advanced organisms that suddenly appeared on Earth about 540 million years ago. Odaraia This may have contributed to the dominance of creatures with mandibles, such as insects, in modern times.
Arthropod fossils Odaraia It was discovered in 1912 in what is now called the Burgess Shale Fossil Region in the Canadian Rocky Mountains.
Jean-Bernard Caron, Royal Ontario Museum
“The evolution of the mandible created a feeding frenzy,” says Alejandro Izquierdo Lopez, an evolutionary biologist at the University of Toronto who led the new study published July 23. Proceedings of the Royal Society B“Animals with mandibles had a huge advantage over their competitors because they could break down larger structures and access new types of food.”
This particular advantage allowed animals with mandibles to rapidly take over the Earth, becoming the most diverse group of animals on the planet. Not least because of this dramatic success, scientists have long been interested in placing the emergence of the mandible in the evolutionary timeline. Big blue Fossil helps you do just that.
“First, we needed to identify a Cambrian fossil with a clearly visible lower jaw,” says Izquierdo Lopez. Big blue Fossils would be better candidates. “These features are very small, so we wanted to look at larger organisms from sites known for being well preserved.” Finding these features in such old specimens, which date back to the beginning of the arthropod fossil record and contain other very primitive features, supports the idea that these animals, which belong to an evolutionary family called Odaraiidae, were among the first to evolve mandibles. Animals with these mouthparts likely lived in less developed ecosystems, which may have made it easier for early food chains to form.
Odaraia They also had a second feeding advantage: their relative large size. Most animals at the time lived in small schools and rarely ventured far. Small creatures were confined to schools where food particles were highly concentrated. But larger creatures could feed more efficiently and were not trapped in the dense concentrations of life and food in the ocean. Freed from the confines of the seafloor, Odaraia Individuals can roam the open ocean as they please.
Until recent studies, scientists Odaraia Odalids were capable of filter feeding, and Derek Briggs, now a professor of earth and planetary sciences at Yale University, speculated in the early 1980s that their odd shapes suggested they were filter feeders.
“There were no prehensile limbs, and the evidence of torso limbs (which was limited at the time) Odaraia By directing water flow through a shell-like covering, the fish can filter out small animals, Briggs said in an email. Scientific American“Its large eyes suggest that it may have sought out small animals, possibly larvae, in the water to feed on.”
This new study: OdaraiaThe researchers identified about 80 tiny spines on each of the creature’s legs that together form a kind of mesh that can trap particles, revealing the organism’s filter-feeding mechanism.
They are large filter feeders that have evolved mandibles Odaraia This dual advantage put pressure on other animals to adapt faster accordingly, contributing to an evolutionary arms race. Now scientists are turning to unravel new mysteries. Big blue“It’s a structure that hasn’t been seen in any other fossils from that time,” Izquierdo Lopez says. “We have no idea how it evolved or why it’s not seen in other animals.”
