同种介形类壳体的多态性兼及化石介形类的物种鉴定

POLYMORPHISM IN THE OSTRACOD CARAPACE AND THE DIAGNOSIS OF FOSSIL OSTRACOD SPECIES

介形类个体发育过程中壳体形状及各种构造的多态性,以及各种外界环境因素对分形类壳体各种分类特征形态变化的影响是十分明显的。该文较系统地阐述了在介形类个体发育中壳体形状、大小、肌痕、边缘毛细管带、边庭、铰合构造及纹饰的变化,并介绍了成年期雌、雄性壳体及左、右壳瓣在形态上的差异;列举了环境因素(主要是水体温度、含盐度、深度)对介形类壳体各分类特征形态变化的影响。基于以上事实,提出了古生物工作者在介形类化石鉴定中应注意的一些问题并讨论了某些描述术语的具体标准。

Polymorphism is a very important and common phenomenon to which more attention should bepaid by palaeontologists,especially students of fossil Ostracoda. There is abundant evidence that ostra-cods exhibit considerable variation in shape, size, muscle scars, radial pore canals, vestibulae, hingestructure and carapace ornamentaion during ontogeny. This ontogenetic polymorphism is considered in detail in this paper. Sexual dimorphism and dimor-phism between the right and left valves in the adult carapace are also discussed. The variation in cara-pace morphology caused by various environmental factors (principally salinity, temperature, waterchemistry, water depth and geographical isolation)is being debated by various authors. This type of eco-logically or geogral,hicaUy induced polymorphism is much more common than many authors seem tounderstand. The method of diagnosis of fossil ostracod species, and particularly the description of newspecies, is considered and discussed in detail,taking into consideration the facts expressed above.