'Abnormal Shrimp' From Cambrian Era Terrorized the Seas, Piercing Its Prey With Its Spiky Facial Appendages

Anomalocaris canadensis, which means "abnormal shrimp from Canada," is one of the earliest and most peculiar apex predators of the sea. It was believed to be a gentle eater, contrary to previous assumptions. Rather than crushing trilobites with their facial appendages, new research indicates that this ancient hunter likely targeted soft-bodied prey in the water.

The findings of the study, titled "Raptorial Appendages of the Cambrian Apex Predator Anomalocaris canadensis Are Built for Soft Prey and Speed," were published in the July 12 edition of Proceedings of the Royal Society B.

Debunking Previous Assumptions

The cause of injuries observed on Cambrian trilobites found in Canada's well-preserved Burgess Shale has been a longstanding mystery, lead author Russell Bicknell, a postdoctoral researcher at the American Museum of Natural History in New York City, explained to Live Science.

One hypothesis suggested that A. canadensis, with its spiky appendages, might have been responsible for the damage by grabbing and piercing its prey.

A. canadensis, resembling a shrimp, had a size of approximately 3 feet (1 meter), which included its intimidating facial appendages. Earlier research utilizing bite force models proposed that tough trilobites were not part of the apex predator's diet. However, the new team of scientists approached the question from a different angle.

The researchers employed 3D computer models of A. canadensis based on available fossil evidence. They also studied modern arthropods like whip spiders (Amblypygi) and whip scorpions (Uropygi) to serve as contemporary analogs for the ancient Cambrian creature. The focus was on understanding how these present-day arthropods used their appendages to grasp and immobilize their prey.

Upon analysis, the team reached the conclusion that although A. canadensis possessed the ability to capture prey effectively, its delicate facial appendages would have been incapable of piercing through the tough exoskeletons of trilobites.

Bicknell explained that trilobite exoskeletons likely had a chemical composition similar to the cuticle of a horseshoe crab's exoskeleton. As a result, attempting to deal with harder prey would have likely damaged the spikes on A. canadensis' appendages.

Shrimp-Like Creature Suited for Preying on Soft-Bodied Animals

Previous studies had indicated that Anomalocaris, due to its mouth parts, was not capable of consuming hard food. So, Bicknell and his team focused their investigation on whether the creature's long and spiny appendages could effectively handle trilobite prey, CNN reported.

By studying modern counterparts, such as whip scorpions and whip spiders, which possess similar appendages for grasping prey, the researchers were able to demonstrate the functionality of Anomalocaris' segmented appendages in capturing and flexing.

The researchers concluded that the ancient predator's spiky limbs were proficient at seizing prey, resembling the grasping abilities of present-day whip spiders. However, these appendages were likely too delicate to engage well-armored prey effectively.

Furthermore, the team discovered that Anomalocaris moved most efficiently when its appendages were fully extended, resembling the outstretched arms of Superman in flight.

As per Science News, these findings suggest that Anomalocaris was ideally suited for pursuing and ensnaring soft-bodied creatures swimming in the water, using its spiky appendages to puncture them. The study's implications extend to the notion that even the earliest predators may have possessed specialized hunting abilities, highlighting the complexity of ancient ecosystems.

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