Exoskeletal abnormalities in paradoxidid trilobites from the Cambrian of Spain, and a new type of bite trace

Abstract

Exoskeletal abnormalities in middle Cambrian paradoxidid trilobites from Purujosa (Eastern Iberian Chain, NE Spain) are herein analyzed for the first time. Two distinct types are reported. The first is represented by triangular or asymmetrical V-to W-shaped breaks on margins of isolated sclerites (cranidia, free cheeks and hypostomes). The second group is represented by shortened thoracic pleural spines in complete or nearly complete individuals. Possible causes of these injuries are discussed, but in some cases a single cause/effect explanation is not apparent. A new ichnotaxon, Mandibulichnus serratus nov. ichnogen., nov. ichnosp., is erected to refer to serrated breakage of the margins of isolated trilobite sclerites produced by active predation or scavenging.