Enrollment and thoracic morphology in paradoxidid trilobites from the cambrian of the Czech Republic

Abstract

The discovery of the partially enrolled specimens of large, late holaspid specimens of paradoxidid trilobites Paradoxides paradoxissimus gracilis, Hydrocephalus minor and Acadoparadoxides cf. sacheri, together with the investigation of functional morphology of their thorax suggest that these arthropods were able to enclose their bodies. The different morphology of thoracic tergites and different outline of the trunk implies different enrollment styles in these species. Consequently, it is possible to distinguish four styles of enrollment within the family Paradoxididae. This variability of enrollment styles not only extends our knowledge about enrollment of paradoxidid trilobites, but also widens our view to diverse protective adaptations in closely related taxa of one family.