Origin and Evolution of Natural Diversity;Proceedings


Pre-Cenomanian Cheilostome Bryozoa : Current State of Knowledge

Ostrovsky, Andrew N.;Taylor, Paul D.;Dick, Matthew H.;Mawatari, Shunsuke F.

Permalink : http://hdl.handle.net/2115/38439
KEYWORDS : Cheilostomata;Bryozoa;Cretaceous;Diversity


This paper briefly summarizes published and new data on the occurrences of pre-Cenomanian cheilostome Bryozoa following their first appearance in the Late Jurassic. We tabulate all known taxa chronologically, summarize stratigraphical and geographical distributions, and comment on the main morphological innovations that appeared in pre-Cenomanian times. Most early cheilostomes are classified in the suborder Malacostegina. Early cheilostomes were morphologically simple and low in diversity, but were geographically widespread. These features can be explained by the possession of a long-living planktotrophic larval stage, as in Recent malacostegans. Diversification of the suborder Neocheilostomina, which greatly dominates modern and post-Albian bryozoan faunas, began in the Late Albian and coincided with the origin of brood chambers (ovicells) and a presumably short-lived, non-planktotrophic larva. The presence of Late Albian neocheilostomes in both Europe and North America implies that their brief larval life was not an obstacle to achieving a wide distribution and suggests a role for rafting in their dispersal.