Chitinozoan chains and cocoons from the upper Ordovician Soom shale lagerstatte, South Africa: implications for affinity

The Upper Ordovician (Ashgill) Soom Shale lagerstatte preserves chitinozoans on the bedding planes as scattered individuals and, more significantly, in linked chains, in aggregated masses and associated with organic envelopes. Chitinozoan affinites are problematical; but the Soom Shale has a restricted biota providing constraints on hypotheses of relationship. No graptolites or gastropods, which are possible contenders for chitinozoan production, occur. The chitinozoans are, however, associated with conodonts and orthocone cephalopods and, of all the known Soom Shale biota, these organisms present the most likely candidates for chitinozoan origination.