CAMBRIAN BRADORIIDA AND PHOSPHATOCOPIDA (ARTHROPODA) OF THE FORMER SOVIET-UNION

Some 40 bradoriid and phosphatocopid (Arthropoda) species are known fr om the Cambrian of the former Soviet Union. The faunas occur chiefly i n Asia (mostly Siberia and Kazakhstan; also Kirghizia); west of the Ur als bradoriid and phosphatocopid faunas are sparse, occurring in the L eningrad region, Belarus and Estonia. Most specimens are recovered as crack-out material from elastic and impure carbonate rocks; acid resis tant valves from limestones are a minor component of the known faunas. Early Cambrian (Atdabanian-Botomian) faunas are widespread; middle an d late Cambrian faunas are scarcer and are known largely from Siberia and Kazakhstan. Though many species are seemingly short-ranging, curre ntly most have only local biostratigraphic significance, with only a f ew having practical international correlative value. Palaeogeographica lly, faunas west of the Urals show affinites with those of the Early P alaeozoic Baltica and Avalonia palaeocontinents (Olenellid trilobite r ealm). Siberian and central Asian (Kazakhstan, Kirghizia, Gorny-Altay- Mongolian belt) faunas show clear affinities with those of palaeoconti nental South China and eastern Gondwana (Redlichiid trilobite realm).