Records of the Western Australian Museum 18: 209-217 (1996). 
Early Cambrian stenothecoid molluscs from China 
Yu Wen 
Department of Earth and Planetary Sciences, Western Australian Museum, Francis Street, 
Perth, Western Australia 6000, Australia 
Abstract - A new species of Stenothecoides, S. yochelsoni sp. nov., is described 
from the Early Cambrian Huangshandong Member of the Tongying 
Formation in Eastern Yangtze Gorge, western Hubei, China. This species is 
one of the new members of the Yangtze micromolluscan fauna. The 
occurrence indicates that the first appearance of Stenothecoides can be dated 
to the earliest Cambrian, and it is probably the earliest record of the genus. 
Two other Early Cambrian species, Bagenovia cf. sajanica Horny and 
Stenothecoides sp., are described from the Xidashan Formation of Kuruktag, 
Xinjiang, China. 
INTRODUCTION 
In 1979, the writer while making a study of the 
earliest Cambrian molluscs from the Eastern 
Yangtze Gorge of western Hubei, China, recovered 
from acid-residues from the Huangshandong 
Member of the Tongying Formation of the 
Tianzhushan Section, an undescribed species of 
Stenothecoides. The Tianzhushan Section is located 
at the west side of the Dianziliang Primary School 
at Tianzhushan, Liantuo, about 25 km northwest of 
the city of Yichang. The Huangshandong Member, 
a richly fossiliferous unit, is composed mainly of 
purplish brown arenaceous-rudaceous dolomites, 
intercalated with striped siliceous phosphorites, 
about 1.88 m in thickness. It conformably overlies 
the Precambrian Baimatuo Member of the 
Tongying Formation and is overlain 
disconformably by the Early Cambrian Shuijingtuo 
Formation (Zhao et al. 1980). 
The material in the arenaceous-rudaceous 
dolomites was preserved in association with other 
elements of the Yangtze micromolluscan fauna, 
such as Tchangsichiton notabilus Yu, Sinoconus 
clypeus Yu, Yangtzeconus priscus Yu, Obtusoconus 
rostriptutea (Qian), Purella tianzhushanensis Yu, 
Igorella hamata Yu, Archaeospira ornata Yu, 
Maclurites hubeiensis Yu and Heraultipegma 
yunnanense He and Yang (Yu 1979, 1984a, b, 1985, 
1987, 1990; Qian, Chen and Chen 1979; He and 
Yang 1982). Of all the micromolluscs, the most 
interesting and characteristic forms are Y. priscus, 
A. ornata, O. rostriptutea, I. hamata and H. 
yunnanense. These fossils are widely distributed in 
the Meishucunian Stage in eastern Yunnan, 
western Sichuan and in corresponding beds in 
many parts of the Yangtze Platform. 
Bagenovia cf. sajanica Horny and Stenothecoides sp. 
were collected in 1978 by Zhang Sengui, Nanjing 
Institute of Geology and Palaeontology, Academia 
Sinica, from the base of the Early Cambrian 
Xidashan Formation on the northern slope of 
Mohurshan of the Kuruktag Mountains, Xinjiang, 
China. On the basis of palaeontological and 
lithological characteristics, the Early Cambrian of 
this area has been divided into two formations: in 
ascending order, the Xishanbuluk Formation and 
the Xidashan Formation (Zhang 1983). 
The Xidashan Formation is about 88 m in 
thickness (Zhang 1983). It is composed chiefly of 
blackish-grey, arenaceous limestones and 
argillaceous limestones with a basal bed of 
purplish-grey, arenaceous, lenticular limestone. 
The basal bed yields a rich fauna of trilobites and 
archaeocyathids and some monoplacophorans, 
gastropods, brachiopods and hyolithids. 
Stenothecoids are rare within the fauna of the 
Xidashan Formation, only three specimens being 
obtained; however these include two species 
placed in two genera, namely: Bagenovia cf. sajanica 
Horny and Stenothecoides sp. In association with 
them are the trilobites Metaredlichioides rectangularis 
Zhu and Lin, Chengkouia xinjiangensis Zhu and Lin 
(Zhu and Lin 1983); the archaeocyathids 
Aldanocyathus cf. belvederi (Rozanov), Coscinocyathus 
xinjiangensis Zhang (Zhang 1983) and the molluscs 
Eocyrtolites radiatus Yu and Cyrtodiscus? 
kuruktagensis Yu (Yu, 1986). Among the associated 
fossils, the genera Metaredlichioides and Chengkouia 
are zonal fossils of the Metaredlichioides-Chengkouia 
zone. This zone is widely distributed in the Middle 
Tsanglangpu Stage of southeastern Shaanxi, 
northwestern Sichuan and eastern Guizhou (Zhou 
and Yuan, 1980). Therefore, the basal part of the 
Xidashan Formation is considered to be middle 
Early Cambrian, equivalent to the Middle 
Tsanglangpu Stage in eastern Southwest-Central 
