摘要
尽最大努力、利用一切有效手段对古植物进行整体研究和重建已成为现代古植物学的一个首要任务,因为只有这样才有可能在比较充分的基础上来探讨古植物的生态、生物学性质、个体发育和系统发育关系。由于植物本身的特殊性,材料的不完整性更为严重。自上世纪以来开展的器官表型分类仍然在古植物学中有着不可替代的价值,有些学者甚至把它作为植物进化的证据。不过,由于植物性状的异级性而使结论的可信程度大大降低。本文对古植物重建的方法据引实例作了综述,对重建的意义也作了较深入的讨论。
It has become a primary goal of modern palaeobotany to study and reconstruct fossil plants in full so far as sufficient evidence is available, because a better understanding of palaeoecology, biology, development and phylogenetic relationships of fossil plants is possible only when they are more completely known. In so doing, the biggest obstacle to overcome is the fragmentary character of the material. Although incompleteness is a common deficiency for almost all fossil groups, the complex life history, the short duration of attachment to the mother plant of reproductive organs (also leaves or branches of deciduous plants) and the open, often indeterminate and modular growth architecture of plants cause the situation much worse than it is in most animal groups (Knoll and Rothwell, 1981). The difficulties in restoring whole plants also lie in the fact that the correlation among organs is always less pronounced in plants than in animals, especially vertebrates. It is even more difficult to reconstruct a fossil plant when its disintegrated portions (or organs) were transported to and deposited in various areas and preserved in different ways. For these reasons, the organ-phenetic classification of fossil plants initiated in the last century still plays an unreplaceable role in recording the fragmentary discoveries. Practically, it is useful in ecological and biostratigraphical studies. Some palaeobotanists even make an attempt at exploring the potential evolutionary or phylogenetic implication of the isolated organs, particularly the reproductive organs, including the important works of Chaloner (1967), Hickey and Doyle (1977) and Meyen (1984). The disadvantage is, however, obivious as heterobathmy is so common that it is usually impossible to envisage the whole-plant based on the limited information obtained from isolated organs. In order to study and reconstruct fossil plants in part or in full, it is necessary to obtain an abundant material by mass collecting. Most ideal are plant fossils preserved in situ or those which have suffered little transportation. The highly valuable specimens are those which bear intact ovules, spores or pollen, or two or more organs in organic connection. Palaeobotanists also take morphological consistency, and similarity in cuticular structure of the associated isolated organs as the important evidence. The discovery of pollen grains in the micropyle or pollen chamber of gymnospermous ovules usually provides a sound basis for linking the pollen-bearing organs with the ovulebearing ones (Zhou, 1983a). The recurrent occurrence of the same organ-assemblage or of different organs in the same plant assemblage in different localities may be regarded as evidence in a lower degree of certainty. Besides the organic reassembling of the whole fossil plants, palaeobotanists also aim at uncovering the full range of their variation. According to the principle of heterochrony (Rothwell, 1987), such variation may be served for phylogenetic interpretation of fossil plants. Futhermore, a full understanding of the morphological variation would possibly prevent specific (or generic) determination of fragmentary specimens from uncertainty and incorrectness in a greater degree and would materially lessen the unnecessary inflation of taxa. There is no doubt that a more completely known fossil plant would contribute much to our knowledge of classification and phylogeny of plants. Both the dramatic discoveries of pteridosperms and progymnosperms are well-known examples. It is obvious that such fossil plants would also provide the basis for biological and ecological interpretation. In this sense, they may be considered as more or less entire biological entities rather than simple assemblages of isolated plant debris. It is expected that major progress in palaeobotany will be made in China as more and more whole fossil plants are studied and reconstructed.
出处
《古生物学报》
CAS
CSCD
北大核心
1992年第1期117-126,共10页
Acta Palaeontologica Sinica
关键词
植物化石
整体重建
plant fossils, reconstruction, whole-plant biology.
