Richness of Famennian-Tournaisian (late Devonian-early Carboniferous) bryozoans in shallow areas of Palaeotethys and Palaeoasian oceans

Abstract

Based on the analysis of data on bryozoan localities in territory of modern Eurasia, changes of the bryozoan richness were calculated in detail for six time slices in the interval from the early Famennian to the late Tournaisian. Highest extinction tempo was observed for the latest Famennian, apparently linked to the Hangenberg Event. However, in the richness of bryozoans during the late-latest Famennian, an abrupt increase in the origination tempo is observed, as well as a slight decrease in the total bryozoan richness at the Devonian-Carboniferous transition. Origination of abundant narrowly specialised bryozoan genera in the orders Trepostomata and Cryptostomata at the end of the Devonian and in the beginning of the Carboniferous was caused by the combined influence of extrinsic and intrinsic factors. An observed increase in the morphological specialisation of bryozoans during the Late Devonian and early Carboniferous coincides with patterns observed in other benthic organisms such as brachiopods and rugose corals. These patterns can be explained by vacation of ecological niches and changes in the structure of the marine biota in the aftermath of the Hangenberg Event.