Palaeobiology and biostratigraphy of Ordovician Chitinozoa from Sweden

Eight publications on Ordovician Chitinozoa from southern Sweden are reviewed (for formal thesis purposes) and supplemented. The biological affinities of chitinozoans and their parasites are discussed. Findings support the theory that chitinozoans are eggs and egg capsules of marine metazoans informally designated as chitinozoophorans. Bacteria, Actinomycota and lower Fungi caused borings into chitinozoan vesicles, but ectoparasitic nanoorganisms are also found on chitinozoans. The distribution of chitinozoans shows that spawning took place mainly in shallow water, but very high water energy was clearly unfavourable to most chitinozoophorans, at least for their reproduction. Some chitinozoans are restricted to or concentrated in a certain type of sediment. These were probably attached to firm objects by vagile chitinozoophorans. Other chitinozoans show no preference for a specific type of sediment, and these may have been dispersed unattached in the water by chitinozoophorans that were holoplanktic or merely planktic during the spawning season. It is concluded that Ordovician chitinozoans have great stratigraphical value in Baltoscandia, especially during the Llandeiloan–Ashgillian.