Institute of Geology, Adam Mickiewicz University, Poznań
Abstract: Variability in the suspected behaviour and general physiology of the Rugosa is inferred from frequently appearing morphotypes in solitary forms. This discussion is preceded by a review of important skeletal and suspected soft features, supported mainly by external characteristics of fossils, combined with some macrostructural data derived from thin sections. Features discussed include mesenteries, tentacles, cilia, morphology of the oral disc, and early ontogeny with particular emphasis on skeletogenesis. Existing skeletal data has led to the proposal of an initial development of two pairs of mesenteries. They were considered to be directive mesenteries by comparison with other Anthozoa. Only the sclerosepta corresponding to these two pairs of mesenteries were considered as protosepta. Complete mesenteries were considered to correspond to major septa, and incomplete ones to minor septa with some variants present in taxa with contratingent minor septa. Further reconstructions of soft parts led to the proposal of two rings of tentacles, corresponding to the major and minor septa and systems of muscle fibrils similar to that in other Anthozoa. The cardinal fossula was reconstructed as an important irrigation apparatus, leading to a siphonoglyph above it, but not forming sufficient space to host mesenteries earing gonads. Also, openings or small slits in the oral disc, corresponding to individual interseptal loculi, were proposed as a means of increasing effectiveness in water circulation in the deep and narrow calices of some aulate taxa. Earlier studies have shown clear differences between the skeletal morphology in juvenile and mature parts of many rugose corals. This is discussed in detail using several examples, beginning with reconstruction of earliest skeletogenesis. Secretion of the attachment and first wall of the aseptal cup is postulated as the initiation of the skeletogenesis of the polyp. Two pairs of mesenteries may have been already present, but the first sclerosepta appeared only after secretion of the cup either immediately or during its accretional growth, but prior to the appearance of the first furrows. Some important behavioural aspects of the Rugosa, such as symbiosis with green algae or bathymetry are shown to be inadequately supported by existing data and, therefore, too premature for discussion.
Key words: Rugosa - polyp morphology - physiology - behaviour
