Evidence item

We describe Yujingia glutenotunica, an ambulacrarian from the early Cambrian Chengjiang biota (518 Ma). Yujingia combines a simple cylindrical body plan with a crown of specialized appendages, including pinnate arms bearing filter-feeding grooves and alternating side-branches. Phylogenetic analyses recover Yujingia within a grade of tentaculate fossils immediately basal to the last common ancestor of all modern ambulacrarians. These results suggest that ambulacrarians evolved from semi-sessile organisms with complex suspension-feeding adaptations, otherwise only found in crown-group echinoderms and tentaculate hemichordates (pterobranchs).