Systematics, taphonomy and palaeoecology of selected invertebrates from the late ordovician Soom Shale Lagerstätte, South Africa

The diversity of the Late Ordovician Soom Shale Lagerstatte ecosystem is increased by the identification of three new species. The phyllocarid arthropod Caryocaris cedarbergensis n. sp. is described, extending the geographical, ecological and temporal range of the family Caryoarididae and providing the first evidence of a zooplanktonic constituent in the Soom Shale biota. The scolecodont species Xanioprion? n. sp. is distinguished, based on poor material and the species Syntaptogenys rietvleiensis n. gen., n. sp. is described, providing the first documented scolecodont fauna from South Africa and the first apparatus based taxonomic study of specimens from Gondwana.;Two new soft-bodied organisms, which would both have had an extremely low preservation potential, are added to the Soom Shale ecosystem. A scyphozoan medusoid exhibits features that can be related to those observed in modern scyphozoans and is the second zooplanktonic organism identified in the Soom Shale ecosystem. A xenusiid lobopodian, showing features homologous to those of other Palaeozoic marine lobopodians, is the first definite marine lobopodian to be described outside of the Cambrian and adds a rare benthic component to the Soom Shale ecosystem.;The recognition of three new types of arthropod, comprising large carapaces of unknown affinities, a possible nektonic crustacean and a nektonic predatory stem-group chelicerate, increase the diversity of arthropods in the Soom Shale ecosystem, and confirms the arthropods as the most diverse fauna from the Soom Shale community.;The identification of fibrous clay mineral coatings, which could be a result of diagenetic or metamorphic growth, complicates the current models for the taphonomy of the Soom Shale. An additional preservation mechanism, pyrite mineralization, occurs along with clay and alunite replacement, organic films and the late stage fibrous clay growth.