Evolution and Fossil History

The rich fossil record of bryozoans allows us to make several generalizations about the pattern of bryozoan evolution through geological time even in the absence of a robust phylogeny. Estimates of diversity at different taxonomic levels for geological periods and stages give a broad impression of the waxing and waning of bryozoans in time. Phases of major radiation and, conversely, of mass extinction are clearly evident. It is also possible to evaluate the diversity dynamics of co‐existing clades, notably cyclostomes and cheilostomes that have co‐existed for the last 150 million years. Convergence is a major theme of bryozoan evolution, both at colony and zooid levels, and the fossil record contains some striking examples of homeomorphy