First report of paired ventral endites in a hurdiid radiodont

Schematic organisation of frontal appendages of different radiodont families. a Amplectobeluidae and Anomalocarididae. One marks first podomere in distal articulated region, bearing hypertrophied endite. Five marks podomere where endite is longer than on podomere 3 in Amplectobeluidae, but not Anomalocarididae. b Tamisiocarididae. One marks first podomere in distal articulated region. c Hurdiidae. One marks first podomere in distal articulated region, 5 marks most distal podomere bearing elongate endite. d Attachment of paired endites to podomere in Amplectobeluidae, Anomalocarididae, and Tamisiocarididae (cross-sectional view). e Single blade-like endite attached to podomere in Hurdiidae (cross-sectional view