Chapter 12 A review of the Early Palaeozoic biogeography of bryozoans

Abstract

The palaeogeographical distributions of Early Palaeozoic bryozoan faunas are reviewed. Previous studies are examined and new databases have been assembled of the stratigraphical and geographical distribution of Ordovician and Silurian taxa. Analysis was carried out using cluster analysis based on Jaccard’s coefficient and paired group method, as well as principal coordinate analysis based on Jaccard’s coefficient, to examine the relationships between different localities. Bryozoan faunas increased in diversity throughout the Ordovician peaking with 133 genera during the Katian. In the earliest Ordovician provincialism is difficult to determine, but by the Darriwilian five distinct provinces developed, decreasing to four in the Sandbian. There was a decrease in provinciality throughout the Katian as faunas became less endemic, caused by the reduction of geographical barriers. Following the extinction of many genera at the end of the Ordovician, early Silurian faunas contain remnant taxa. Subsequently fenestrates began to dominate faunas. During the Llandovery bryozoans began to show distinct provincialism, but this declined during the Wenlock, only to re-emerge during the Ludlow. Late Silurian (Pridoli) faunas are sparse but nevertheless show possible division into two provinces.

Diversity dynamics of Ordovician Bryozoa

“…; Buttler et al . ). An increase in provincialism leads to the diversity increase due to higher level of isolation, whereas in the time of low faunal provincialism, the diversity drops significantly (e.g.…”

“…Besides the global events, local factors played an important role for the bryozoan diversity dynamics, such as the type of the marine basin (epicontinental vs. open marine), geographical position (tropical vs. high latitude) as well as plate tectonic configuration which influenced the faunal provincialism (e.g. Anstey 1986;Tuckey & Anstey 1992;Taylor & Ernst 2004; Jim enez-S anchez & Villas 2010; Rasmussen & Harper 2011;Finnegan et al 2012;Buttler et al 2013). An increase in provincialism leads to the diversity increase due to higher level of isolation, whereas in the time of low faunal provincialism, the diversity drops significantly (e.g.…”

The oldest known bryozoan: Prophyllodictya (Cryptostomata) from the lower Tremadocian (Lower Ordovician) of Liujiachang, south‐western Hubei, central China

“…However, much more research needs to be undertaken on the evolutionary palaeobiogeography of early bryozoans (Buttler et al . ) to test and refine these apparent patterns of origination and dispersion.…”

Temporal area approach for distributional data in biogeography

“…These matrices do not have temporal information except the taxon's precise age range, representing a single 'snapshot' of a time. Examples of fixed temporal matrices include Crisci et al (1991), De Grave (2001) and Buttler et al (2013). Temporal data matrices represent multiple periods or epochs within the same data matrix, through the temporal partitioning of areas and the listing of occurrences relevant to each partition.…”