Branch diameters within some species of sponges, corals, and bryozoans are known to decrease with depth. This relationship is here tested for inferring relative depth of deposition using three ramose, bushlike cyclostome bryozoans—Cinctipora elegans, Diaperoecia purpurascens, and Erksonea sp.—that are abundant on the continental shelf around New Zealand. Diameters were measured in broken branches of these species dredged from 15 benthic stations ranging in depth from 38–668 m. The expected inverse correlation between diameter and depth was apparent only in C. elegans and even then at a low level of significance and only at relatively shallow depths (<∼115 m). No depth pattern was discernible in either D. purpurascens or Erksonea sp. Further research is needed to ascertain exactly which depth-related environmental factor(s) influences branch diameter in cyclostome bryozoans and whether different species respond differently before bryozoan branch diameter can be used in paleobathymetry.

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