A new radiodont (stem Euarthropoda) frontal appendage with a mosaic of characters from the Cambrian (Series 2 Stage 3) Chengjiang biota

Abstract

Abstract The classification of Radiodonta is primarily based on the morphology of their frontal appendages, a main feeding structure of this iconic group of mostly Cambrian stem‐group euarthropods. However, recent progress in the description and revision of radiodont taxa, particularly drawing on their frontal appendages, has exposed morphological variation that challenges reliable identification of higher‐level groupings. Here we describe a new taxon of Radiodonta, Laminacaris chimera gen. et sp. nov., from the Cambrian Series 2, Stage 3, Chengjiang biota of China, based on its unique frontal appendage morphology. Laminacaris is distinctive for its combination of characters shared by hurdiids and other early Cambrian radiodont families. Elongated, possibly unpaired endites on two proximal podomeres that bear small distally‐directed auxiliary spines oriented perpendicular to the long axis of the endite, are comparable with the elongated endites and their auxiliary spines of all known Cambrian members of Hurdiidae. In contrast, endites on more distal podomeres are similar to some species of Anomalocaris, and the dorsal spines at the distal end resemble those of Amplectobelua. The mosaic characters in the frontal appendage of Laminacaris chimera may capture morphology close to the divergence between the major radiodont groups.