Gastropods from the Permian of Guangxi and Yunnan Provinces, South China

Journal of Paleontology, Jan 2002 by Hua-Zhang, Pan, Erwin, Douglas H

Wuchiapingian Stage.-The Manzanospira turrita-Ploceozyga (Hyphantozvga) matanensis assemblage.-This moderately diverse assemblage contains seven species referred to seven genera including Palaeostylus fusuiensis n. sp., Porcellia paucituberculata n. sp., Soleniscus micidus n. sp., Strobeus sp., and a very abundant turbiniform gastropod. They occur in dark grey, middle bedded bioclastic limestones with chert nodules from the Lower member of Heshan Formation in Heshan county, Guangxi Province. This assemblage differs from older assemblages by the presence of many small gastropods including Manzanospira, Ploceozyga (Hyphantozvga), Soleniscus, and Strobeus and the absence of large euomphalids. The former genera appeared elsewhere in the world much earlier, and they have similar morphologies to species from the American Pennsylvanian, particularly Palaeostylus and Hyphantozyga. This assemblage is associated with Skolithos which burrowed less than 20 cm in depth. The gastropod shells are often found slightly broken and abraded, with most of their sculpture eroded. The limited diversity of this assemblage may reflect a littoral environment with a soft mud substratum unsuitable for gastropods.

Changhsing Stage.-I) Donaldina heshanensis-Ninglangella assemblage.-This assemblage occurs in siliceous limestones from the middle part of the upper member of the Heshan Formation, Heshan and Fusui counties, Guangxi Province and in Ninglang County, Yunnan Province. The assemblage is characterized by a high diversity of 27 genera and 44 species and by genera including Straparollus, Platvzona, Peruvispira, Ploceouga (Hyphantozyga), Pseudozygopleura, Glyptospira, Straparella, Strobeus, Girtyspira, Meekospira, Donaldina, Streptacis and the endemic genera Spinella, Luoguispira, Microlampra, Luoguella, Ninglangella, Plicatus, Propupa, Laxella. All shells are very small and were recovered through acid-etching, preserving the beautiful ornamentation and protoconchs. The Streptacididae is the most abundant family, with eight species referred to three genera. These include Laxella micra n. gen. and sp., Donaldina heshanensis n. sp., D. eleganta n. sp., D. quinquecarinata n. sp., Donaldina. sp., Streptacis regularis n. sp., S. pravis n. sp., and S. fragilis n. sp. The Pseudozygopleuridae and Procerithiidae are also important constituents of the assemblage with six species referred to four genera, including Ploceozyga (Hyphantozyga) n. sp., Microptychis charma n. sp., Ploceozyga (Plocezyga) yuunanensis n. sp., G. (P.) varica n. sp., Pseudozygopleura micra n. sp., Palaeostylus dongluoensis Pan Y. T., and P. fusuiensis n. sp. Some species show evidence of shell boring, with a steep-sided, almost circular hole (Fig. 8.1, 8.3; Fig. 6.5). One hole is very similar to that produced by recent naticids (Fig. 8.1, 8.6). The assemblage is preserved in siliceous limestones, and the facies and fauna suggest deposition in a muddy-sandy tidal flat. The assemblage is associated with Palaeofusulina sinensis and Nankinella minor, the ammonoid Tapashanites and the brachiopods Oldhamina anshusuensis and Orthotetina ruber.