摘要
该文研究的介形类化石材料,系采自云南曲靖潇湘水库剖面和翠峰山剖面晚志留世关底组、妙高组、玉龙寺组、早泥盆世下西山村组和西屯组,计18属、30种和1亚种,其中包括1新属、12新种和1新亚种。推测Parasargentina属及其种群代表晚志留世;玉龙寺组(包括面店村组)归入上志留统较为合适。根据豆石介类“大颚肌痕”特征,建议将下西山村组和西屯组一齐划归到下泥盆统下部。关于志留系与泥盆系的界线,置于玉龙寺组与下西山村组之间为宜。文中还就介形类动物群的生态环境作了探讨。
Late Silurian and Early Devonian strata are well--developed and exposed at the XiaoxiangReservoir (Liaojiaoshan) and Cuifengshan sections in the Qujing area and contain abundantbenthic communities. Ostracodes are also very common in these strata,including leperditi-ids, beyrichiids, pachydomellids (e. g. Microcheilinella, Parasargentina), bairdiocypridids (e.g. Cytherellina, Healdianella, Beckerina),cavellinids (e. g. Cavellina, Sulcella, Uchtovia),eridoconchids (e. g. Cryptophyllus), etc. In this paper, the ostracodes are described and illus-trated by Wang and Liu except leperditiids and beyrichiids, including 18 genera (including 1new genus,Beckerina), 30 species (including 12 new species) and 1 new subspecies (Table1), while 9 species are dealt with under open nomenclature. The ostracode assemblages fromthe above--mentioned strata are characterized by the predominance of endemic species. Recent discovery has revealed that (in ascending order) the Kuanti Formation (includingYuejiashan Formation),Miaokao Formation and the lower part of the Yulungssu Formationalso contain conodonts in addition to benthic communities (Wang Cheng--yuan 1980, 1981);the conodont Ozarkodina crispa therein indicates late Ludlovian to early Pridoli in age. The Yuejiashan Formation(=lower part of Kuanti Formation) was dated as Wenlockianmainly based on the ostracode Bolbibollia labrosa Ulrich et Bassler found by Jiang (Fang etal., 1985). The genus (type species: B. labrosa) has a characteristic horseshoe--shaped ridgearound S_2 according to its definition,but this structure does not seem to be developed in thespecimens of B. labrosa as reported by Jiang, which may be a different genus and speciesfrom B. labrosa Ulrich et Bassler, 1923. The genus Parasargentina and its type species P.sinensis were established and described by Zheng (1982) from Silurian strata of Jiangyou,Sichuan; B. sinensis, P. subsinensis sp. nov. and P. subsinensis indistincta subsp. nov. may beconsidered as important members constituting the ostracode assemblage of the Kuanti For-mation besides beyrichiids. Shi and Wang (1987)reported 2 species of Parasargentina, P.sinensis and P. acuta Shi et Wang, 1987 from the Upper Silurian Yanglugou Formation ofTewo, West Qinling Mts. In our presumption, the strata containing Parasargentina and itstype species P. sinensis as recorded by Zheng (1982) from Jiangyou may be younger than theLower and Middle Silurian based on analysis mentioned above and other relevant material.Therefore,this genus and its species association probably indicate Ludlovian to Pridoli age. The ostracode assemblag of the Yulungssu Formation is closely related to that of the Miaokou Formation because a lot of species are common to both strata, such as Commotento-mozoe corduroides (Grabau), 1926 (with C. sinensis Jiang, 1983 as its synonym) and Cytherelli-na subovata (Zheng) 1982. This paper is inclined to refer the Yulungssu Formation (includ-ing its upper part) to the Upper Silurian. Members of the Beyrichia--Hexophthalmoides As-semblage proposed by Jiang (Fang et al., 1985) from the upper part of this formation are on-ly known from the Cuifengshan Formation based on his descriptions (Jiang, 1983; Fang etal., 1985). Therefore,it may be untenable to assign the upper part of this formation to theLower Devonian together with the Cuifengshan Formation based on the ostracode assem-blage. The Xiaxishancun Formation (= Xishancun Member of Cuifengshan Formation) yieldsleperditiids and beyrichiids in its lower part but beyrichiids and eridoconchids in its upperpart. This paper tends to place the Xiaxishancun Formation in the Lower Devonian, which isprobably assignable to the Lochkovian stage, because (a) up to now, no leperditiids havebeen recorded from the Silurian in China,especially in South China;and (b) leperditiids oc-curring in the lower part possess curved--conic 'mandibular muscle scar'(trailing chevron),with its lower end lying at or slightly below the center in front of the adductor muscle scar asin Sinoleperditia guangxiensis Wang (1989) from the upper Lochkovia
出处
《微体古生物学报》
CSCD
北大核心
1992年第4期363-389,465-468,共27页
Acta Micropalaeontologica Sinica
关键词
介形亚纲
晚志留世
早泥盆世
Ostracoda
Upper Silurian to Lower Devonian
taxonomy
biostratigraphy
paleoecology
