The trouble with trilobites: classification, phylogeny and the cryptogenesis problem

Trilobites are an iconic group of extinct arthropods that lived in Palaeozoic oceans for c . 270 Ma, before their demise at the end of the Permian Period. Despite their considerable diversity (> 22 000 species) and abundance, particularly in Cambrian and Ordovician rocks, as well as intensive study for well over 200 years, trilobite systematics remains in a state of flux. In this contribution, the complex history of trilobite classification...