Paleobiologic and evolutionary significance of corallite increase and associated features in Saffordophyllum newcombae (Tabulata, Late Ordovician, southern Manitoba)

Saffordophyllum newcombae Flower, 1961, displays unique abilities and an un precedented range in types of corallite increase. Cerioid growth was charac teristic, but colonies on soft substrates could grow in a tollinaform manne r during early astogeny. The capacity for recovery from damage and partial mortality is amazing. Rejuvenation may have been accompanied by peripheral expansion in some cases. Rapid regeneration could involve axial increase. C ircular lacunae that formed during recovery became sites of rapid lateral i ncrease or corallite decrease. Two types of axial increase occurred within coralla. Lateral increase was c oncentrated mainly along the basal wall and adjacent to certain circular la cunae. In typical cerioid parts of the corallum, lateral increase seldom yi elded "adult" corallites, but incipient lateral offsets could be numerous. The level of colony integration was probably moderately high. There was lik ely soft-tissue continuity among polyps, coordination of polyp behavior, su bjugation of individuals for the good of the colony, and perhaps astogeneti c control. Saffordophyllum newcombae is considered to be a tabulate coral, although on e type of axial increase is similar to that in a few rugose corals and the other type of axial increase as well as possible peripheral expansion resem ble modes of increase in some coralline sponges. Lateral increase is consid ered compatible with cnidarian rather than poriferan biology. Corallite siz e is typical of tabulates. Saffordophyllum may not be the direct ancestor o f favositid tabulates, and may not even be closely related to them; S. newc ombae is very different from Paleofavosites and Favosites. The remarkable range in forms of increase discovered in S. newcombae demons trates the critical need for detailed paleobiologic studies, if we are to u nderstand the early evolutionary history of corals and to establish reliabl e criteria for distinguishing various coral groups and homeomorphs.