Apex predator of the Cambrian likely sought soft over crunchy prey

Newswise — Biomechanical research on the arachnid-like fore "limbs" of a prehistoric top predator reveals that Anomalocaris canadensis, a marine creature measuring 2 feet (60 centimeters), probably possessed less strength than previously believed. As a colossal organism from the Cambrian era, it likely exhibited swiftness and agility, swiftly pursuing vulnerable prey in open aquatic environments rather than engaging in the pursuit of hard-shelled organisms residing on the oceanic bed. Today, the findings are published in the journal Proceedings of the Royal Society B.

Initially unearthed during the latter half of the 19th century, Anomalocaris canadensis, a Latin term denoting a peculiar shrimp originating from Canada, has been conventionally attributed to the marked and fragmented exoskeletons of trilobites discovered in paleontological archives.

"The notion didn't resonate with me, as trilobites possess an exceptionally robust exoskeleton formed primarily from rock-like material, whereas this organism would have predominantly consisted of soft and pliable tissues," expressed Russell Bicknell, the principal author of the study. Bicknell, a postdoctoral researcher affiliated with the Division of Paleontology at the American Museum of Natural History, conducted the research during his tenure at the University of New England in Australia.

Newly conducted investigations into the armored, circular mouthparts of A. canadensis raise skepticism regarding the creature's capacity to consume hard sustenance. The most recent study aimed to explore whether the predator's elongated, prickly anterior appendages could fulfill that function instead.

The initial phase for the team of researchers, comprising scientists from Germany, China, Switzerland, the United Kingdom, and Australia, involved constructing a three-dimensional representation of A. canadensis. They accomplished this by utilizing exceptionally well-preserved, albeit compressed, fossils of the creature unearthed from Canada's Burgess Shale, dating back 508 million years. By drawing comparisons with contemporary whip scorpions and whip spiders, the team successfully demonstrated that the predator's segmented appendages possessed the ability to seize prey, as well as the flexibility to extend and contract.

To analyze the grasping capabilities of A. canadensis, the research team employed a modeling method known as finite element analysis. This technique enabled them to visualize the areas of stress and strain experienced during the organism's grasping behavior, providing insight into the potential damage that would occur when attempting to capture hard prey such as trilobites. Additionally, the researchers utilized computational fluid dynamics to simulate the creature's swimming behavior by placing the 3D model within a virtual current. This approach allowed them to predict the most probable body position adopted by A. canadensis while navigating through the water.

By employing these combined biomechanical modeling techniques, which were utilized together for the first time in a scientific publication, a revised understanding of A. canadensis emerges, deviating from previous assumptions. The findings suggest that the creature was probably a swift swimmer, dashing after vulnerable prey in the water column while extending its front appendages. This new depiction challenges previous notions about the predator's behavior and sheds light on its ecological niche as a hunter in aquatic environments.

Russell Bicknell remarked that previous understandings portrayed the Burgess Shale fauna as an unrestricted buffet for these creatures, suggesting that they could pursue any prey at will. However, the current research reveals a more intricate and nuanced perspective on the food webs of the Cambrian period. The findings indicate that the dynamics of these ancient ecosystems were far more complex than previously envisioned. This realization prompts a reassessment of the role and interactions of A. canadensis within the broader ecological context of the time.