An atlas of malformed trilobites from North American repositories. Part 1. The Indiana University Paleontological Collection (American Museum novitates, no. 4026)

Abstract

Malformed trilobites have been well documented within the arthropod fossil record and serve as valuable evidence for illustrating aspects of trilobite paleoecology associated with development, predation, and pathologies. Ongoing efforts to comprehensively document these malformations have uncovered important, often unique records for the extinct group, shedding light on post-malformation recovery processes and potential predators. A key means of recording new examples of these specimens has been the examination of historically important paleontological collections. To expand this approach, we examined the Deiss collection in the Indiana University Paleontology Collection and present four examples of malformations from Cambrian (Asaphiscus wheeleri, Dorypyge bispinosa, Wanneria walcottana), and Ordovician (Isotelus iowensis) species. These specimens reveal evidence of injuries, failed predation, and developmental complications. We explore the possible explanations for malformations and consider the current state of the art for evaluating trilobite malformations. Finally, the Deiss collection history and its ongoing contributions to Paleozoic fossils are presented.