Abnormalities in early Paleozoic trilobites from central and eastern China

Malformations are common in trilobites, but the majority of described specimens are from Europe and North America. Only a few abnormal trilobites have been reported from China. Ten abnormal trilobites from Cambrian, Ordovician and Silurian strata in central and eastern China are documented. The abnormal Ordovician trilobites are found for the first time in China. All malformations occur in the thoraxes and pygidia, and were caused by a sub-lethal predatory attack, genetic or embryological malfunction, or injury sustained during molting. It is difficult to identify the predators of the six injured trilobites, but potential predators include Cambrian non-trilobite arthropods, Ordovician cephalopods, and Silurian eurypterids, chondrichthyes or cephalopods, even cannibalistic trilobites. Abnormal specimens caused by sub-lethal predatory attacks mainly occur in Cambrian strata in China and other areas in the world, and are rare in post-Cambrian strata. This pattern may reflect the rise of predators and increased predation in the post-Cambrian, which led to an increased trilobite fatality rate, thus reducing the probability that injured specimens would become fossilized. (C) 2021 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.

Automated summary

Abnormal trilobites from Cambrian, Ordovician, and Silurian strata in central and eastern China are documented, with malformations mainly occurring in the thoraxes and pygidia. These abnormalities are attributed to sub-lethal predatory attacks, genetic or embryological malfunction, or injury during molting. Predators of the injured trilobites are difficult to identify, but potential ones include Cambrian non-trilobite arthropods, Ordovician cephalopods, and Silurian eurypterids, chondrichthyes, or cephalopods. Abnormal specimens caused by sub-lethal predatory attacks are rare in post-Cambrian strata, possibly due to increased predation and trilobite fatality rates.