Late Ordovician well-preserved radiolarians occurred from black organic mudstones and calcareous mudstones of the Malongulli Formation of the Lachlan Fold Belt, southeastern Australia. Paleontological study provides significant informations for evaluation of origin of radiolaria, and their evolution in Early Paleozoic. This also may render an additional data on the nature of well diversified Early Paleozoic radiolarians, and record first appearence of ancestoral Ceratoikiscum of Albaillellaria and some forms of Palaeoscenidiidae.
Radiolarians described herein are grouped into 14 genera and 26 species. They consist of Entactinia, Entactinosphaera, Haplentactinia, Haplotaeniatum Kalimnasphaera, Inanigutta, Secuicollacta, Palaeoscenidium, Palaeotripus, Palaeotrifidus, and proposed one new genera related to Ceratoikiscum and undescribed forms.