Yang, Z. D. (1985). 贵州郎岱打铁关“茅口石灰岩”中(竹蜓)类化石的再研究 - Restudy of fusulinids from the “Maokou Limestone" (Permian) at Datieguan, Langdai Guizhou,. 微体古生物学报 - Acta Micropalaeontologica Sinica. 2(4): 307-338+425-427.

300241

Yang, Z. D.

1985

2(4): 307-338+425-427

Publication

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Datieguan is situated about 10 km southeast of the Langdai Town in Guizhou Province, from where the famous "Maokou Limestone" was named. The marine Lower Permian sediments there are well-exposed and completely developed clear stratigraphical sequence containing very abundant fusulinid foraminifers. Owing to precipitous terrain and inaccessible communication, this standard section has never been measured practically and the fusulinid fos- sils contained therein have not yet been collected and studied systemically since the term "Maokou Limestone" was first porposed by Yue(1929)and later revised by Huang(1932)more than 50 years ago. This situation has been hindering the study of Lower Permian biostratigraphy in China from going further and has become an urgent problem which must be solved as soon as possible.The materials in this paper were all collected from Datieguan by the writer in the autumn of 1980 while going on field work to measure the section there. The fusulinids described and illustrated comprise 151 species and subspecies belonging to 31 genera, including 1 new genus,13 new species and 6 unnamed species. All these species with their stratigraphical distributions are listed in the Chinese text(pp.309—310).The "Maokou Limestone" , according to Yue’s definition(1929), is a set of Early Permian carbonate sediments. There the fusulinids of Verbeekinacea, beginning with the appearance of Misellina in the lower part and ending respectively at the developmental zenith of Afghanella, Sumatrina and Yabeina in the upper part, underwent a complete evolutional process, in which the septula changed from lacking to existing, from imperfect to perfect in shape, from few to many in number and from simple to complex in type and arrangement. These changes may be shown by the numerous thin slices of fusulinids from every bed of the"Maokou Limestone" in the Datieguan section. Based on these first-hand materials, the phylogeny of Neoschwagerinidae can be recognized in detail. This family consists of two branch systems, i.e.Neoschwagerininae and Sumatrininae. The former is developed through such a lineage as Maklaya?Neoschwagerina ex gr. simplex?Neoschwagerina ex gr. craticulifera?Yabeina, and the latter as Shengella?Cancellina?Praesumatrina?Afghanella, Sumatrina, both originating from Misellina, or more exactly to say, from the different species of Misellina.Shengella(gen.nov.)can be distinguished from Misellina by the presence of septula, and it differs from Maklaya in the larger form ratio,the thinner walls and the narrow and high parachomata. However, the septula of Shengella are primitive and imperfect, not yet devEloped into axial septula, so that there are apparent differences between Shengella and Cancellina. In addition, Shengella was derived directly from Misellina and then developed immediately into Cancellina; this evolutional procedure is quite similar to that of Maklaya, which was developed from Misellina and then evolved itself into Neoschwagerina ex gr. simplex. Both Shengella and Maklaya not only share certain similarities in the structures of septula, but also associate with each other at the same stratigraphical horizon. This particular assemblage implies the beginning of an important change in fusulinid evolution. Laying emphasis on this special stage, Kanmera and Toriyama (1968) established the genus Moklaya, but they put it roughly in the same position with primitive cancellinids. These so-called "primitive cancellinids" are grouped in the new genus Shengella described in the present paper. Shengella and Maklaya separately occupied the position of a starting point for the two branch systems of Neoschwagerinidae, which underwent further differentiation, exactly representing the developing trends of the two genera.So far as we know, Praesumatrina is characterized by the more and earlier appearance of secondary transverse septula. However, the lower margins of its septula are sometimes slightly dense and thickened in outer volutions. Undoubtedly, these properties are more advanced than those of Cancellina,

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