A faster-paced world?: contrasts in biovolume and life-process rates in cyclostome (Class Stenolaemata) and cheilostome (Class Gymnolaemata) bryozoans

Zooids of cheilostome bryozoans are on average substantially more robust than are zooids of cyclostome bryozoans. The differences include greater number, length, and cross-sectional area of tentacles, plus a more extensively developed funiculus. Median values for mouth size and cilia-generated feeding current velocity are greater for cheilostomes than for cyclostomes so that cheilostomes have the potential for greater intake of nutrient energy per unit time, which may explain their apparently higher growth rates. For unit area of substrate occupied, the Cheilostomata (Class Gymnolaemata; members of the post-Paleozoic fauna) contain greater biomass and apparently generate greater energy flow than do the Cyclostomata, which are the only extant order of the Class Stenolaemata (characteristic of the Paleozoic fauna).