Researchers have identified a healed W-shaped wound on a fossilized swimming flap from a Cambrian-era radiodont, suggesting the predator survived a prehistoric attack.

A 520-million-year-old fossil of a radiodont, an extinct arthropod, shows evidence of a healed bite wound, according to researchers. The specimen, identified as Amplectobelua symbrachiata, was discovered in the Yu’anshan Formation in China. The finding provides rare insight into predator-prey interactions during the Cambrian Period, as the animal appears to have survived an attack that left a distinct W-shaped mark on its swimming flap.

Evidence of a prehistoric attack

The fossilized swimming flap features a W-shaped indentation, a pattern typically associated with fangs tearing through flesh. To verify the injury, researchers used X-ray fluorescence mapping, which confirmed that the chemical composition of the wound area is consistent with the rest of the fossil, ruling out damage caused by the fossilization process or flaking. Furthermore, a black band around the edges of the wound suggests melanization, a process seen in modern arthropods when they regrow tissue after an injury, indicating the animal was alive when the incident occurred.

Context and alternative interpretations

Radiodonts were apex predators of the Cambrian seas, growing to nearly a meter in length and possessing grasping appendages for hunting. While hundreds of predation wounds have been documented in trilobites, this is the first reported instance of a healed injury in a radiodont. Some experts, such as Joe Moysiuk of the Manitoba Museum, suggest that injuries can also occur during the molting process when arthropods shed their exoskeletons. However, Stephen Pates of University College London argues that the W-shape and the specific location of the wound are more characteristic of a bite mark sustained while the animal was fleeing an attacker.