贵州台江中寒武世的一些软舌螺化石

SOME MIDDLE CAMBRiAN HYOLITHIDS FROM TAIJIANG, GUIZHOU

该文的软舌螺标本采自贵州省台江县八郎村中寒武世地层,计有Haplophrentis?reesei,H.?carinatus,Hyolithes?cf.idahoensis,H.?cf.cariniferus,H.?sp.,Cambrovitus balangensis gen.sp.nov.,Notabititidae gen.et sp.uncertain.。其层位位于梅树村动物群和澄江动物群之上。地层时代与北美布吉斯页岩的时代相当,两地的软舌螺可直接对比。更为可贵的是在方Haplophrentis?carinatus的腹内视标本中发现了直肠和伸缩肌软体印痕。

This paper describes some hyolithids from the middle and upper parts of the Middle CambrianKaili Formation at Balang Village of Taijiang County,southeastern Guizhou. The Kaili shale is similarin age to the Burgess shale of British Columbia. These hyolithids can be directly compared with thosefrom the Burgess shale; therefore, their discovery is of significance to the taxonomy of the MiddleCambrian hyolithids. Our study will throw new light on the paleontology and geographic distribution ofthe Burgess shale type biota. In addition, the hyolithids from Taijiang together with those previouslydiscovered from the Lower Cambrian Meishucun and Chengjiang faunas would make up anevolutionary succession. According to Malinky and others'study, most species (except the type species)which have beenassigned to Hyolithes, should be reassigned to other genera. For this reason, Hyolithes? carinatusMatthew, 1899, is here reassigned to the genus Haplophrentis Babcock et Robison, 1988. The authorsalso agree with Babcock and Robison that the genus Haplophrentis includes H. reesei Babcock etRobison, 1988 (type species)and H. carinatus (Matthew, 1899), but are doubtful about the basis forsetting up the genus Haplophrentis. Some species are provisionally retained in Hyolithes? because of nowell--preserved specimens available for determining their generic character. In one specimen of Haploph-rontis? carinatus, the soft part of hyolithids has been described; many conches referred to hyolithids arearranged in certain preferential direction which may indicate the direction of paleocurrents.