Выпуск: 3 , Том: 25 , Год издания: 1984

Rich new graptolite assemblages have been identified on the Siberian Platform in-Kuznets Alatau an d Gornyi Altai in continuous cross sections at the Cambrian-Ordovician boundary. Chitinozoa have been found with them in analogs of the Lower Tremadocian. This lets us assume that the first chitinozoa appear in the Lower Tremadocian, in the zone of flabelliforme (s. l. ). The base of the Tremadocian is the preferred boundary between the Cambrian and Ordovician since the rise of plankton graptolites and shitinozoa is confined to it.