“Unveiling the Cambrian Abyss: The Fascinating Dance of Punctured Shells and Their Predators”

The swift rise in variety and prevalence of biomineralizing species during the Early Cambrian period (approximately 535 million years ago) is frequently linked to predation and an evolutionary arms race. Discussions surrounding the Cambrian arms race are typically framed on a macroevolutionary scale, especially regarding escalation. Nonetheless, while there are plentiful fossils evidencing early Cambrian predation, concrete proof of adaptive responses to predation remains insufficient. To investigate the Cambrian arms race hypothesis, paleontologists from the University of New England, the American Museum of Natural History, and Macquarie University evaluated a substantial sample of minute fossilized shells from the tommotiid species Lapworthella fasciculata sourced from South Australia, with over 200 specimens showing punctures created by a perforating predator.

The 517-million-year-old shells of Lapworthella fasciculata. Image credit: Bicknell et al., doi: 10.1016/j.cub.2024.12.007.

“Interactions between predators and prey are frequently regarded as a crucial factor in the Cambrian explosion, particularly concerning the rapid rise in variety and number of biomineralizing species during this era,” stated Dr. Russell Bicknell, a paleontologist at the American Museum of Natural History.

“Nevertheless, there has been a lack of concrete proof indicating that prey directly reacted to predation, and similarly, vice versa.”

An evolutionary arms race describes a scenario where predators and prey perpetually adapt and evolve in response to one another.

This relationship is often characterized as an arms race, as enhancements in one species’ capabilities prompt improvements in the other species’ abilities as a counteraction.

Dr. Bicknell and his team investigated an extensive collection of fossilized shells from an early Cambrian tommotiid species, Lapworthella fasciculata, collected from South Australia.

More than 200 of these incredibly small specimens, varying from slightly larger than a grain of sand to just smaller than an apple seed, exhibited holes likely created by a hole-punching predator—most probably a type of soft-bodied mollusk or worm.

The paleontologists examined these specimens concerning their geological ages and observed an increase in shell wall thickness correlated with a rise in the quantity of perforated shells within a brief timeframe.

This indicates that a microevolutionary arms race was underway, with Lapworthella fasciculata evolving mechanisms to strengthen its shell against predation while the predator simultaneously adapted to enhance its piercing abilities despite its prey’s thicker defenses.

“This critically valuable evolutionary record illustrates, for the first time, that predation played a crucial role in the expansion of early animal ecosystems and demonstrates the rapid pace at which such phenotypic changes emerged during the Cambrian Explosion event,” Dr. Bicknell remarked.

The research was published in the journal Current Biology.

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Russell D.C. Bicknell et al. Adaptive responses in Cambrian predator and prey underscore the arms race during the rise of animals. Current Biology, published online January 3, 2025; doi: 10.1016/j.cub.2024.12.007