210 
Yu Wen 
China (Zhang 1983; Zhu and Lin 1983; Yu 1986). 
Specimens described in this paper are all 
deposited at the Nanjing Institute of Geology and 
Palaeontology, Academia Sinica. 
STENOTHECOIDES AND BAGENOVIA 
Stenothecoides has mainly been reported from the 
Early Cambrian of east Greenland (Poulsen 1932), 
Laborador and Yukon Region of Canada (Resser 
1938, Yochelson 1968, 1969), Siberia (Homy 1957; 
Missarzhevsky in Rozanov and Missarzhevsky 
1966; Aksarina 1968, Aksarina and Pelman 1978), 
central Kazakhstan (Koneva 1979) and western 
Mongolia (Zhegallo 1982), and the Middle 
Cambrian of United States (Walcott 1884, 1886; 
Robison 1964), British Columbia of Canada (Rasetti 
1954), central Kazakhstan (Koneva 1979) and 
central North Greenland (Peel 1988). During the 
last two decades, this genus has been extensively 
found in China. It has been collected from the 
Huangshandong Member of the Early Cambrian 
Tongying Formation of Eastern Yangtze Gorge, 
western Hubei, the Early Cambrian Xidashan 
Formation of Kuruktag, Xinjiang and the Early 
Cambrian Tianheban Formation of Xianfeng of 
Hubei and other places (Figure 1). Of the material 
from these formations, that from the Eastern 
Yangtze Gorge is a bivalved, asymmetrically 
inequivalve form. According to previous records, 
most species of the genus Stenothecoides occur only 
as a single non-articulated valve. Only a few 
species were preserved in a bivalve condition, e.g., 
Stenothecoides knighti Yochelson (1969: 59-60, fig. 2) 
from the Early Cambrian of Yukon, Canada, S. 
siberica (Aksarina) (Aksarina and Pelmen 1978:115, 
pi. XVII, figs. 4-6) from the Early Cambrian Lenian 
Stage of Siberia, S. bellus Koneva (1979: 26, pi. V, 
fig. 1) from the Early Cambrian Lenian Stage of 
central Kazakhstan and Stenothecoides sp. 
(Yochelson 1969: 51, fig. 1) from the upper Early 
Cambrian of Siberia. 
So far as I am aware, most of the Early Cambrian 
species of Stenothecoides are associated with 
trilobites or archaeocyathids. However, the new 
species of Stenothecoides described herein is found 
with a micromolluscan fauns that predates the 
trilobites. It therefore possibly represents the 
earliest record of Stenothecoides. Therefore, the first 
appearance of Stenothecoides can be traced back to 
the very earliest Cambrian. Furthermore, it is a 
new member of the Yangtze micromolluscan fauna, 
which occurs in the earliest Cambrian 
Meishucunian Stage of the Yangtze Platform in 
China. As such it is the first biomineralisation 
event in the evolutionary history of invertebrates 
in the Phanerozoic. It also represents the first stage 
of the diversification in the history of Phylum 
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