Emergence and extinction of the Givetian to Frasnian bryozoan faunas in the Kostomłoty facies zone, Holy Cross Mountains, Poland

Abstract

Devonian bryozoans have been investigated from two Givetian to Frasnian localities in the Holy Cross Mts (Central Poland), representing fossiliferous ramp slope facies of the Kostomloty facies zone (north-western periphery of the Kielce carbonate platform). Thirteen genera belonging to four families and three orders have been identified. Bryozoans show close relation to previously described Givetian and Frasnian bryozoan faunas of France, but also some affinities to easterly regions (e.g., Kuzbass). The main immigration episodes are related to late Givetian and middle Frasnian deepening pulses. The replacement of locally rich and diverse Givetian carbonate bank faunas by overall impoverished Frasnian reef-complex associations largely corresponds to a major extinction event in the evolutionary history of Bryozoa. Five new species are described by 1. Morozova and O. Weis: Eridotrypella arguta, Eridotrypella exserta, Eostenopora nimia, Primorella nitida, Primorella indigena.