The Oryctocephalid Trilobites And Their Biostratigraphic Significance From Balang Formation Of Cambrian,Guizhou Province,China

The Balang Fauna occurs in the middle-upper parts of the Balang Formation of Cambrain from Guizhou. Oryctocephalid trilobite is one of the significant compositions of Balang Fauna, Due to Banglang Formation has a wide distribution in eastern Guizhou, several localities of the Balang Fauna have been found. Based on the arrangement and classification for the Oryctocephalid trilobites yielded from three of the localities, these trilobites were differentiated into 6 genera and 8 species including a new genus and a species as follows: Arthricocephalus chauveaui Bergeron, Arthricocephalites xinzhaiheensis Chien et Lin in Lu et al., 1974,Arthricocephalites intermedius Zhou in Lu et al., 1974,Balangia balangensis Chien, 1961,Changaspis elongate Lee in Chian, 1961,Duyunnaspis duyunensis Chang et Chien, 1977, Duyunnaspis lazizhaiensis sp. nov. and Jianheaspis jiaobangensis gen. et sp. nov.. By the taxonomy rediscussion of A.(Arthricocephalites) and the comparision with Arthricocephalus, they are differently belong to genus-level species, and A.(Arthricocephalites) should be recongnized as Arthricocephalites.. Using the methods of ontogenetic analysis and mathematical statistic, study on ontogeny of 3 species: A. chauveaui,Ar. xinzhaiheensis and Ar. intermedius, we recongnize Ar. xinzhaiheensis has 8 thoracic segments and 5 rings in axis of pygidium, while the Ar. intermedius only has 6 thoracic segments and 6 rings in the pygidium, furthermore, the three species are different in meraspid period, and the data of mathematical statistic analysis from specimens of both Ar. xinzhaiheensis and Ar.intermedius supports to merging 11 species of original A.(Arthricocephalites) into two species Ar. xinzhaiheensis and Ar.intermedius, according to naming priority rules.By investigating the strata distribution of A. chauveaui,Ar. xinzhaiheensis,Ar. intermedius,C. elongata,D. duyunensis, above species all occur in in Jiaobang section and Lazizhai section of the Balng Formation, Jianhe County and Geyi section of the Balang Formation, Taijiang County, A. chauveaui and Ar. xinzhaiheensis distribute from the lower part of sections to the upper part of the formation. Ar. intermedius appears higher than the Ar. xinzhaiheensis and ranges to uppermost of the formation. C. elongate appears from the middle part to the upper part of the formation.. D. duyunensis appears from the middle-lower part to the uppermost of the fromation. The A. chauveaui,Ar. intermedius,Changaspis elongata also occur in the Henson Gletscher formation in northern Greenland, therefore, 3 species are widespread species. Due to Ar. xinzhaiheensis only occurrenced in China, the biostratigraphic framework of the Balang Formation established the A. chauveaui Zone to help the correlation of global strata in the same period.