The early Cambrian <i>Kuamaia lata</i>, an artiopodan euarthropod with a raptorial frontal appendage

Abstract Phylogenetic analysis demonstrates that Kuamaia lata , a helmetiid euarthropod from the lower Cambrian (Series 2, Stage 3) Chengjiang Konservat-Lagerstätte, nests robustly within Artiopoda, the euarthropod clade including trilobitomorphs. Microtomography of new specimens of K . lata reveals details of morphology, notably a six-segmented head and raptorial frontal appendages, the latter contrasting with filiform antennae considered to be a diagnostic character of Artiopoda. Phylogenetic analyses demonstrate that a raptorial frontal appendage is a symplesiomorphy for upper stem-group euarthropods, retained across a swathe of tree space, but evolved secondarily in K . lata from an antenna within Artiopoda. The phylogenetic position of K . lata adds support to a six-segmented head being an ancestral state for upper stem- and crown-group euarthropods.