Functional significance of contrasting colony form in two mesozoic encrusting bryozoans

Mesozoic bryozoan faunas are dominated by two cyclostome form-genera, Stomatopora and Berenicea. Encrusing colonies of Stomatopora and Berenicea are respectively linear with zooids arranged in branching uniserial rows, and discoidal with zooids arranged in a multiserial sheet. Functional morphological analysis indicates that Berenicea colonies were physiologically and hydrodynamically better integrated than Stomatopora colonies and were also more successful at competing for substrate space. However, Stomatopora colonies had the abilitu to locate spacial refuges where mortality was decreased. The comparatively opportunistic mode of life inferred for Stomatopora is substantiated by apparent absence of larval brooding. Stomatopora was propably an early successional genus normally replaced by Berenicea during later ecological succession except in palaeoenvironments experiencing high levels of disturbance. Stomatopora is more like to have been ancestral to Berenicea than vice-versa.