Healed injury in a nektobenthic trilobite: “Octopus-like” predatory style in Middle Ordovician?

Abstract

The Lower Paleozoic sediments of the Barrandian area are globally renowned as a classical example of well-preserved skeletal marine fauna, including abundant remains of trilobites. Several tens of morphologically anomalous exoskeletons of trilobites have been collected and docu-mented from Cambrian to Devonian clastic sediments and carbonates. One of them, an excep-tionally well preserved, articulated and partly enrolled exoskeleton of the Ordovician nektoben-thic trilobite Parabarrandia bohemica (NOVÁK, 1884) exhibits a prominent palaeopathological anomaly in its pygidium. We interpret this anomaly as a healed traumatic injury and attribute this damage to a failed predatory attack. The subsequently healed injury is classified as the ichno-genus Oichnus BROMLEY, 1981. The structure on the pygidium is strongly reminiscent of injuries caused by octopods and a large cephalopod is proposed as a potential durophagous predator responsible for the herein described trilobite injury. However, an attack from an unknown arthropod while the trilobite was in a soft-shelled stage cannot be excluded.