Healed predation scar on a Cambrian apex predator

Predation is considered a key driver of the rapid diversification of animals during the Cambrian explosion. While the fossil record documents a plethora of evidence of successful and failed predation on biomineralized invertebrates at low trophic levels, no previous evidence of predation on larger, often soft-bodied, animals at higher trophic levels has been reported. This means that the modeled links between higher trophic levels in Cambrian food webs lack supporting fossil evidence, hindering understanding of the complexity of Cambrian trophic relationships. Here, we report a healed injury on the swimming flap of the radiodont apex predator Amplectobelua symbrachiata-- one of the largest animals in the Cambrian oceans. The diagnostic W-shape with a healed margin supports interpretation of this wound as predatory in origin, with likely attackers including larger contemporaneous radiodonts - possibly members of the same species -- or the giant lobopodian Omnidens. Evidence that apex predators were attacked provides critical empirical data informing the complexity of Cambrian food webs. This finding provides empirical support for the existence of high-level feeding loops, analogous to those in modern marine ecosystems, documenting the rapid increase in trophic complexity during the latter stages of the Ediacaran-Cambrian Transition.