Reappraisal of New Zealand and Australian Ordovician caryocaridids presents insight into phyllocarid phylogeny

Caryocaridids exhibited a wide geographical distribution and high diversity during the Great Ordovician Biodiversification Event. The global geographical distribution, limited taxonomic examination and lack of insight into preservational conditions have collectively contributed to an inadequate systematic assessment of Ordovician caryocaridids. To address this situation, we re-examined Ordovician caryocaridid specimens from Australia and New Zealand. Considering these findings, we establish Rhinopterocaris fordycei sp. nov. This new species is characterized by the presence of a well-developed anterior carapace horn, a rounded, truncated posteroventral margin, and furcal rami that lack triangular expansion and spines. In doing so, we confirm the validity of Rhinopterocaris. We reclassify specimens of Lingulocaris maccoyi Etheridge, 1892 into Rhinopterocaris maccoyi (Etheridge, 1892) and highlight that specimens previously reported as Rhinopterocaris maccoyi belong in Jellicaris stewarti. A phylogenetic analysis of 44 Paleozoic phyllocarids reveals that Rhinopterocaris is basal within caryocaridids and is a sister group to younger caryocaridids. Finally, we present a hypothetical evolutionary lineage of caryocaridids and explore the evolutionary history of the group.