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一、概述无洞贝类是泥盆系地层中分布最广、最常见、最丰富的腕足动物之一;和其它某些腕足动物相比,它具有分布广、历时短、特征明显等特点,应该具有一定的地层意义。然而由于以往对其研究不够,因而它在划分、对比地层上的作用尚未充分显示。近廿年来,某些学者对此类化石进行了一系列较深入的研究,其内部构造逐渐被揭示,所谓无洞贝(At- rypa)这样一个繁杂的属逐渐解体,许多新属和亚属相继建立,它们彼此的关系、地质
I. Overview The cave-free shellfish is one of the most widely distributed, most common and abundant brachiopods in the Devonian strata. Compared with some other brachiopods, it has the characteristics of wide distribution, short duration and obvious characteristics. It should have some stratigraphic significance. However, due to its lack of research in the past, its role in dividing and contrasting strata has not yet been fully demonstrated. In recent 20 years, some scholars have conducted a series of deeper studies on these fossils, and their internal structures have been gradually revealed. The so-called complex genus At-rypa gradually disintegrates and many new genera and subgenus Successively established, their relationship to each other, geology