Functional morphology of the shell in platycope ostracodes - a study of arrested evolution
Functional morphology of the shell in platycope ostracodes - a study of arrested evolution
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扁平足介形类外壳的功能形态——停滞进化研究
DOI：
10.1111/j.1502-3931.1985.tb00687.x
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发表时间：
1985
期刊：
影响因子：
1.5
通讯作者：
V. Jaanusson
中科院分区：
文献类型：
--
作者：
V. Jaanusson
根据切片法、连续剥离法和薄切片法，描述了现代种深水苏铁贝壳与软体部分相关的形态。卵囊的重要功能特征包括瓣膜间角质层(‘韧带’)沿着强烈的曲线广泛发育，因此在开放的甲壳中瓣膜之间的腹缝非常狭窄，以及一种特殊的卵子护理方式，这与一种独特的(本土)类型的性贝壳二型性有关。扁形介形类代表了一种明显保守的进化谱系；它们的基本特征在志留纪已知的最早的真正扁形类中已经充分发育。进化缓慢的原因被认为是几乎不可能改变它们特定的形态组织来适应某些其他的生活方式或在给定的形态框架内广泛地多样化。这显然同样适用于舌状腕足动物，可能也适用于其他迟钝的类群。
Shell morphology in relation to soft parts is described in the modem species Cytherella abyssorum G. O. Sars, based on microtome sections, serial peels and thin sections. Functionally important features of the cytherellids include the extensive development of the intervalvar cuticle (‘ligament’) along a strongly curved Line, the consequently very narrow ventral slit between valves in opened carapaces, and a special mode of egg care which is associated with a distinctive (domatial) type of sexual shell dimorphism. Platycope ostracodes represent a pronouncedly conservative evolutionary lineage; their essential characters are fully developed already in the earliest known true platycopes from the Silurian Period. The cause of the slow evolutionary change is suggested to have been the virtual impossibility to change their specific morphological organisation to fit some other mode of life or to diversify widely within the given morphological framework. The same obviously applies to the lingulaccan brachiopods and probably also other bradytelic groups.