Abstract

During the Carboniferous, changes in the biogeographical distribution of shelf-dwelling, benthic marine invertebrates were made in response to changes in physical paleogeography and climatic variations. Calcareous foraminifers and bryozoans are principal examples of the general trends during the Early Carboniferous, which show that Tournaisian and early and middle Visean faunas were broadly cosmopolitan in a circumequatorial belt and that latitudinal diversity gradients were relatively minor. During the later part of the Visean and early part of the Namurian, the Hercynian orogeny, caused by the collision of Euramerica with Gondwana, disrupted these cosmopolitan equatorial faunal patterns. This was also a time of progressively cooler temperatures throughout the world, of dramatic reduction in faunal diversity, and of high rates of extinction of both species and genera.

During middle Carboniferous time, strongly provincial faunas were common. Spasmodic, but limited, dispersals gave a few widespread genera significantly different stratigraphic ranges in different provinces so that Tethyan and non-Tethyan distributions are recognizable. Faunal diversity gradually increased during the middle Carboniferous and then declined at the end of the epoch with additional high levels of extinction of species and genera.

During late Carboniferous time, several new faunal lineages became well established. Some filled vacant ecological niches; however, others took advantage of the increase in the number of niches that became available because of gradually warming climates. Provinciality continued to be pronounced. Diversity gradually increased and continued to do so through the Early Permian.

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