Early Evolution of Phyllocarid Arthropods: Phylogeny and Systematics of Cambrian-Devonian Archaeostracans

Abstract

A phylogenetic analysis and review of Paleozoic phyllocarid systematics is presented using morphology-based characters from Cambrian to modern taxa. The resulting cladograms of the Phyllocarida suggest that the suborder Ceratiocaridina as traditionally defined (families Ceratiocarididae and Caryocarididae) is paraphyletic. Caryocarididae is subsequently elevated to subordinal rank with the erection of Caryocaridina n. suborder, resulting in two monophyletic suborders.Haplocarisn. gen. is erected to contain Caryocarididae taxa without triangular spine-like projections of the anterior telson margin. Emended diagnoses, quantified with morphometrics where appropriate, are integrated into this analysis, and result in synonymy of many Cambrian—Silurian caryocaridids and ceratiocaridids with pre-existing taxa. Two representatives of the Leptostraca are included in this analysis. A visual key of well-established representatives of the Ceratiocaridina is presented and suggestions are offered that will help to improve the long-term stability of the Archaeostraca.