The question of whether branching and budding in halysitid tabulate corals was regulated by the availability of nutrients or exposure to waste products is important for taxonomy. Moreover, such regulation could have implications for paleoenvironmental interpretation. Although the statistical and morphological evidence presented here is not unequivocal, it is suggested as a working hypothesis that halysitid astogeny was indeed regulated. This would be in accordance with current theories on the growth of Recent corals and sponges. The simulation results are used to reevaluate functional advantages of the regulation of the halysitid colony.

Key words: Halysitidae, Tabulata, astogeny, ecophenotypes, models.

Oyvind Hammer [ohammer@toyen.uio.no], Paleontological Museum, University of Oslo, Sars gt. 1, 0562 Oslo, Norway.