New radiolarian morphotype discovered from the Dalong Formation, Hushan, east suburb of Nanjing

Nagai Hiromi, Yang Qun and Wang Yu-jing

pp. 85-93, 1 plate, in English, with Chinese abstract

Abstract:

Microfossils of most likely radiolarian affinity were extracted from a siliceous shale sample collected in the Upper Permian Dalong Formation Hushan section, Tangshan area, east suburb of Nanjing. The Changhsingian age (latest Permian) of the Dalong has been established by ammonite and conodont biostratigraphy. The newly discovered conical of spindle-shaped microfossils, isolated from a siliceous matrix of the Dalong Formation using standard HF method, resemble the Mesozoic radiolarian genus Archaeodictyomitra Pessagno, but differs from the latter by having more massive and less numerous costae with only relict pores. X-ray energy dispersion data show that the shell composition is predominantly siliceous. It is likely that these forms belong to a different radiolarian genus of the latest Palaeozoic age. This is the first time that such radiolarian forms are found in Upper Permian strata, which could potentially be used as an agediagnostic index fossil for the latest Permian strata. A formal taxonomic description of the new morphotype is considered premature due to the preservational status that prevents an examination of the internal structure.

Keywords: Radiolaria, Upper Permian, Dalong Formation, Nanjing