Abstract

Records of Cambrian and early Ordovician ectoprocts (bryozoans) are still sparse, and the earliest forms have so far proved to be poorly preserved. The profusion of ectoprocts in the later part of the early Ordovician and early part of the middle Ordovician show a great morphological diversity. The ectoproct fauna of the Chazyan, New York and Vermont, is one such burst in the evolution of the early ectoprocts. These Chazyan ectoprocts in North America and those in Estonia and Siberia indicate that certain lineages were well established in these widely separated areas and probably established on a world-wide basis. These show several different types of colony construction and zooecial structures. At least 11 lineages form the Chazyan ectoprocts: ceramoporoids, escharoporids, pachydictyids, stictoporids, phylloporinids, nicholsonellids, eridotrypids, atactotoechids, batostomids, jordanoporids, and heloporids?.

The Chazyan species of ectoprocts were ecologically adapted to certain shallow neritic environments. The ceramoporoids apparently colonized new areas on the Chazyan shelf area and built up the substrate which other organisms could then invade. Batostoma was important in building bio-herms and in binding sediment. Other ectoproct species built scattered thickets or grew between larger thickets of ectoproct colonies and sessile benthos.

This summary study advocates that the term Ectoprocta, widely used in neontology, be used in paleontology in place of the term Bryozoa, which includes forms that differ widely in their basic organization.

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