摘要
电子显微镜下研究表明 ,Palaeofusulina的旋壁由致密层及“透明层”组成 ,“透明层”的晶粒形状、大小和排列方式与旋壁四层式 (Fusulinella型 )中的透明层超微特征有较大的差异。文中应用Palaeofusulina旋壁的透明层一词 ,加以引号 ,以示两者之间的区别。晚二叠世长兴阶的Palaeofusulina属及其旋壁构造相同的若干属均可归于PalaeofusulininaeM . Maclay ,196
Deprat J. established the genus Palaeofusulina in 1912, and the type species Palaeofusulina prisca Deprat 1913 was described in the next year. In his description the spirotheca was said to be composed of a tectum and a keriotheca. His illustrations seeminly are a combination of photographs, retouched photographs, and line-drawing. In some illustrations, including the holotype, obvious retouching of a photograph has produced rather abnormal structural features. The spirotheca of Palaeofusulina, according to Sheng Jing-Zhang (1955), is composed of two layers, a tectum and a diaphanotheca. The genus Palaeofusulina is restricted to the Changhsing stage of latest Permian, which is referred to the fusulinid faunal zone of Palaeofusulina (Sheng, 1955, p.289). Palaeofusulina is the most typical genus of fusulinid foraminifers with a two-layered spirotheca, which is commonly referred to the Palaeofusulina-type of spirotheca (Sheng et al.,1988,p.13). The SEM study has revealed that the tectum, with a thickness varying from 2-2.5 μm,is composed of isometric crystal granules with a diameter generally smaller than 1.0μm, showing no preferred orientation in their arragement. Our SEM examination has shown that the diaphanotheca is 16-20μm thick and is composed of two groups of crystal granules, one group is roughly isometric crystal granules with a diameter about 1.5-2μm, and the group is represented by a series of crystal granules (3-4μm) with a regular shape. The ultrastructural features of the diaphanotheca in the test wall of Palaeofusulina can be distinguished from the diaphanotheca of the Fusulinella-type by its two groups of crystal granules. The genus Palaeofusulina was originally described by A.M.-Maclay (1963,p.228) as an indepedent genus of the subfamily Palaeofusulininae. To date,the following genera have been assigned to this subfamily: Palaeofusulina Deprat, 1912 (Shindella Chedija, 1984), Dunbarula Ciry, 1948 (Paradunbarula Skinner, 1969, Nanlingella Rui et Sheng, 1981, Parananlingella Rui et Sheng, 1981, Pseudodunbarula Chedija, 1984), Gallowayinella Chen, 1934, Tewoella Sun 1979 (Ziguiella Lin, 1980) and Codonofusiella Dunbar et Skinner, 1937.
出处
《古生物学报》
CAS
CSCD
北大核心
2001年第2期239-243,共5页
Acta Palaeontologica Sinica
基金
中国科学院古生物学与古人类学科基础研究特别支持费资助
