Article: A new xenusiid lobopod from the Early Cambrian Sirius Passet fauna of North Greenland

Three incomplete specimens of a large lobopod, Hadranax augustus gen. et sp. nov. are described from the exceptionally preserved Sirius Passet fauna (Buen Formation, Lower Cambrian, North Greenland). Its overall appearance and size are similar to those of Xenusion auerswaldi Pompeckj from the Baltic, but H. augustus differs in its possession of four poorly defined dorsal nodes in each row rather than two, and in the probable possession of a pair of long, branched frontal appendages.The new specimens further demonstrate that the lobopods were a widespread and diverse Cambrian group. The presence of a four-noded xenusiid refutes the hypothesis that lobopods were directly derived from tetraradial nemathelminthes and shows that both node number and form were fairly flexible, although their primary function remains unclear. The probable presence of a pair of long branched frontal appendages in H. augustus removes one of the major reasons for considering Xenusion to be a basal lobopod, and adds further to the characters that unite Anomalocaris-like taxa to the lobopods.