皖南石台地区奥陶系牙形刺

ORDOVICIAN CONODONTS FROM THE SHITAI REGION, ANHUI

本文研究了安徽省石台地区奥陶系红花园组至汤山组牙形刺的组合特征及其序列,共发现了牙形刺36属64种。文中描述其中地层意义较大的12属16种。建立了12个牙形刺化石带,其中一组合带。自上而下为: Hamarodus europacus带;Amorphognathus superbus带;Amorphognathus tvearensis带; Baltoniodus variabilis带;Pygodus anserinus-Eoplacognathus jianyeensis带; Pygodus serrus带;Eoplacognathus suecicus带;Amorphognathus variabilis带; Paroistodus originalis带; Periodon flabellum带;Oepikodus evae带; Serratognathus tangshanensis带。 本区奥陶系牙形刺的面貌属北大西洋生物地理区。这些牙形刺化石带基本上可与我国宜昌地区、宁镇地区以及西欧奥陶系的牙形刺化石带进行对比。

The Ordovician is well-developed in the Shitai Region located on the southeastern fringe of the Yangzi Stratigraphic Province. In order to make clear the features of rocks and conodont faunas of the Ordovician, the writers have investigated into the region for three times since 1979, measuring the Ordovician sections and collecting about four hundred samples which yielded a rich conodont fauna, containing a total of about 64 species in 36 genera, including one new species.In this region, twelve conodont zones can be established in ascending order as follows:1. Serratognathus tangshanensis zone;2. Oepikodus evae zone;3. Periodon flabellum zone;4. Paroistodus originalis zone;5. Amorphognathus variabilis zone;6. Eoplacognathus suecicus zone;7. Pygodus serrus zone;8. Pygodus anserinus-Eoplacognathus jianyeensis zone;9. Baltoniodus variabilis zone;10. Amorphognathus tvearensis zone;11. Amorphognathus superbus zone and12. Hamarodus europaeus zone.These zones can be correlated with those of the Nanjing Region in Jiangsu, the Yichang Region in Hubei and those of West Europe.Description of New SpeciesAcodus shitaianus sp. nov. (P1. Ⅴ, figs. 26—31)Species under study including acodiform, distacodiform and scandiform elements composed of a symmetrical transition series.Acodiform element with a round costa on only one side, which extends from tip to aboral margin. Cusp abruptly narrowing, erect to recurred. Base big; antero-basal angle sharp. Oral edge forming little processes. Aboral margin triangular. Basal cavity deep.Distacodiform element carrying a costa on each side, which extends from tip to margin. Cusp abruptly narrowing, recurved and symmetrical. Base big; antero-basal angle round. Oral edge short. Basal cavity shallow.Scandodiform element with abruptly narrowing, recurved cusp. Aboral margin straight, Basal cavity shallow.Occurrence Dawan Formation; Lower Ordovician.