Two species of Hesslandona (Phosphatocopida, Crustacea) from the Upper Cambrian of western Hunan, South China and the phylogeny of Phosphatocopida

Abstract

The phosphatocopids Hesslandona necopina Müller, 1964 and Hesslandona longispinosa (Kozur, 1974) new combination, recovered from the Upper Cambrian in western Hunan, South China, are described. The ontogenetic stages of H. necopina are revised, with newly defined second and third ontogenetic stages. The second stage is characterized by a bipartite mandibular limb stem consisting of separate coxa and basipod. The third stage is characterized by the partial fusion of the mandibular coxa and basipod. These two parts may become completely fused possibly in a later ontogenetic stage. Vestrogothia longispinosa Kozur, 1974 is reassigned to Hesslandona because of the presence of an interdorsum and a relatively narrow doublure. The new data reported here, plus earlier reports of phosphatocopids from the same section and horizon in western Hunan since 2005, are included in an updated phylogenetic analysis of the Phosphatocopida. Autapomorphies that define several monophyletic groups (e.g., the Crustacea sensu lato, Labrophora, Eucrustacea, Phosphatocopida, Euphosphatocopida, Vestrogothiina, Hesslandonina, and Dorsospinata) are discussed. The present analysis confirms results from earlier phylogenetic analyses in showing the Phosphatocopida-Eucrustacea sister-taxon relationship, but differs from them in supporting the paraphyly of the Hesslandonidae and the monophyly of the Vestrogothiidae.