Kerygmachela which have lobopodian traits (e.g. lobopodous appendage, annulation) occupied the basal position; while Opabiniidae and Radiodonta are more derived and closely related to the arthropod crown group, with the latter even having significant arthropod affinities such as arthropodization and head sclerites. In the original description, Dinocaridida was composed of only Opabiniidae and Radiodonta. With the exclusion of questionable taxa (e.g. the putative opabiniid Myoscolex), the former were known only by Opabinia, while all radiodont species were grouped under a single family: Anomalocarididae (hence the previous common name 'Anomalocaridids'). In later studies, the gilled lobopodians Pambdelurion and Kerygmachela were also regarded to be dinocaridids, a new opabiniid genus Utaurora was described, other strange dinocaridids like Parvibellus and Mieridduryn, and many radiodonts were reassigned to other new families (Amplectobeluidae, Tamisiocarididae and Hurdiidae). Distribution The group was geographically widespread, and has been reported from Cambrian strata in Canada, United States, Greenland, China, Australia and Russia, as well as the Ordovician of Morocco and Devonian of Germany. Notes References Cambrian arthropods Devonian arthropods Ordovician arthropods Cambrian first appearances Early Devonian extinctions Burgess Shale fossils Maotianshan shales fossils Sirius Passet fossils Paleozoic animals of Asia Paleozoic animals of North America Prehistoric China Paleozoic Greenland Arthropod classes Prehistoric protostome classes Paraphyletic groups