摘要
最近有人认为将化石藻类的分类归入现生藻类分类单元有利于珊瑚藻作为古环境的标志 ,便于理解该类群的演化。然而 ,这样分类可能很难 ,因为并不是所有现生藻类分类特征都能在化石种中保存下来。 Sporolithacea科的钙化部分 (独立或者聚集的孢子囊群 )的出现 ,可以把它们与这个类群的另一个现生科 Corallinaceae区别开 ,这个科在生殖窠中产生孢子囊。节片的有无 ,丝间细胞的联系类型 ,生殖窠中孢子囊释放的数目都是用来划分 Coral-linaceae科的亚科的标准 ,在化石样品中也可以用合适的条件进行观察。在大多数情况下 ,对现生珊瑚藻类属的划分特征可以在化石藻类中鉴别出来 ,但在几种现生珊瑚藻没有钙化的生殖结构或发育特征。因此 ,它们生殖结构无法与相应的化石藻类进行对比 ,也不能进行化石藻类的分类。近年来的趋势认为生殖结构和发育特征是对现生珊瑚藻进行分类的优先鉴定标准 ,然而 ,某些特征的稳定性在属的划分上仍然存在争论。在许多情况下 ,现生藻类的分类标准特征都不能在化石中保存 ,对古生物化石的分类标准的最佳选择是在化石藻类中选择辅助的 ,并且可以识别的其它鉴定特征 。
The application of the taxonomy currently proposed for living algae to fossil plants facilitates the use of coralline algae as palaeoenvironmental indicators and favours the understanding of the evolutionary biology of the group. Such application, however, might be difficult since not all the features used as diagnostic criteria are preserved in fossil specimens. The occurrence of calcified compartments (isolated or grouped in sori) characteristics of the family Sporolithaceae, recognizable in fossil plants, allows them to be readily distinguished from Corallinaceae, the other living family in the group, in which sporangia develop within conceptacles. Presence/absence of genicula, type of the interfilamental cell connections and number of openings in sporangial conceptacles, which are all character states used for delimiting subfamilies within the family Corallinaceae, can also be observed with the appropriate techniques in fossil examples. In most cases, diagnostic features for separating genera in living corallines can be identified in fossil plants. It several other cases, however, proposed diagnostic characters in extant corallines are uncalcified reproductive structures or developmental features that are not preserved and therefore cannot be used for genus identification in ancient material. In recent years there has been a tendency to propose reproductive and developmental features as prevalent diagnostic criteria for living coralline taxonomy. However, the consistency and systematic significance of some of those features for delimiting genera is still the subject of discussion. In cases in which diagnostic criteria are not preserved the best options for palaeontological taxonomy are ancillary characters recognizable in fossil plants, or the application of informal generic names with a broader circumscription than in living representatives.
出处
《微体古生物学报》
CSCD
北大核心
2003年第1期47-56,共10页
Acta Micropalaeontologica Sinica
