Chuck Bednar for redOrbit.com – @BednarChuck
Anomalocaridids, the early ancestors of modern-day day shrimp, were massive creatures that grew to be more than six feet long and looked more like baleen whales than the crustaceans they would eventually evolve into, researchers claim in a new study.
Peter Van Roy, an associate research scientist at Yale University and the lead author of a paper published Wednesday in the journal Nature, and his colleagues examined the remains of a type of anomalocaridid known as Aegirocassis benmoulae, which grew to be up to seven feet long.
“It would’ve freaked people out if they encountered it while they were swimming,” Van Roy told USA Today. “But it would’ve been totally harmless” because it was not a predator. Rather, it was “a very peaceful, meek animal,” he and his colleagues discovered in their research.
Gentle giant
They studied the anatomy of remains recovered from a site in Morocco, and as reported by Discovery News earlier this week, they found that the massive creature would have used special filtering structures to strain plankton and other nutrients out of the water passively using feeding techniques similar to those of modern krill, sponges, clams and even baleen whales.
[STORY: Fossil jaw pushes human origins back 400,00 years]
In contrast, while modern shrimp also eat plankton, they also frequently dine on marine worms and small shellfish, the website noted. They even sometimes go after dead fish or crabs, and can resort to cannibalism at times when there are no other sources of food available.
The researchers also found that the trunk segments of A. benmoulae had flaps resembling the gill flaps or walking limbs found on modern crustaceans, spiders and insects. They even found older, smaller relatives of these creatures, some dating back as much as 500 million years ago that were not adapted for filter feeding, suggesting that shrimp evolution was a complex process.
What the scientists marveled about most, however, was the enormous size of the creature. David Legg, a paleobiologist at the UK’s Oxford University Museum of Natural History who was not involved in the study, told USA Today that the fossil “weighs more than I do.” Upon first seeing the specimen, Legg said he “dropped it on my arm. I’ve never been in so much pain.”
Again, they were stunned by its size
Small pieces of the new species were first found in a Moroccan excavation site in the late 2000s, and Van Roy initially believed that the fragments resembled the body parts of an anomalocaridid (an ancient sea creature whose name roughly translates to “strange shrimp”), the newspaper said.
[STORY: Lost city discovered in Honduras]
However, the fossils simply looked to be too big to belong to the shrimp predecessors. As more and more fossils were found, though, it became increasingly clear that the bits did in fact belong to a massive new anomalocaridid species that lived nearly 500 million years ago. The discovery also suggests that the waters around modern-day Morocco were once rich in nutrients.
“It would have dwarfed anything else at the time, being twice as big as the next biggest animal – at the very least. They were absolutely massive,” Van Roy told The Verge. He noted that when he first saw the two sets of flaps and considered “the implications for the evolution of limbs and for anomalocaridids… I thought ‘jeez, is this really true?’”
“Because these structures are not yet joined together at their base in anomalocaridids, this confirms that anomalocaridids represent a very early stage in the evolution of arthropods,” he explained, adding that while he plans to begin researching other arthropods, that there is also “new material to study” and “much more to learn” about these shrimp ancestors.
—–
Follow redOrbit on Twitter, Facebook, Google+, Instagram and Pinterest.
Comments