Biostratigraphy, Taxonomy, and Paleogeography of Conodont Sequences in the Middle and Late Devonian (Frasnian) Tropics

黑山和阿尔伯塔地区的Frasnian牙形石层序生物地层连续性非常发达，并且保存了代表Palmatolepis生物相的动物群。通过图解对比，这两个区域组成的层序将成为该生物相的参考标准，该生物相具有整个推断泥盆纪热带的外陆架到盆地层序特征。在已发表的关于掌掌藓属（Palmatolepis）和掌掌藓属（Ancyrognathus）的物种鉴定中存在很大的不一致性，导致对Frasnian“标准”分区所依据的两个主要类群的范围的错误理解。此外，对具有内陆架Frasnian层序特征的Polygnathus生物相研究较少。我基于多元素分类学和台地元素形态分析的研究，极大地改变了Palmatolepis和Ancyrognathus的种划分，从而改变了它们的地层范围。结果是Palmatolepis生物相内的带数量几乎增加了一倍，但它们的分辨率远远超过了通过图形对比获得的分辨率。Palmatolepis和Polygnathus生物相之间的对比仍然很困难，但可能通过图解方法来解决。拟议的研究将在整个泥盆纪热带地区广泛分散的地方严格测试这些新的生物地层学和分类学结果，并有一个额外的长期目标，即对弗拉斯尼亚牙形石古地理进行全面分析。

Frasnian conodont sequences in the Montagne Noire and Alberta are superbly developed in their biostratigraphic continuity and excellent preservation of faunas representative of the Palmatolepis biofacies. Through graphic correlation, the sequence composited from these two areas will become a standard of reference for this biofacies, characteristic of outer shelf to basinal sequences throughout the inferred Devonian tropics. There has been great inconsistency in published identifications of species of Palmatolepis and Ancyrognathus resulting in erroneous understanding of ranges of the two principal groups on which the Frasnian "standard" zonation is based. Furthermore, there has been little study of the Polygnathus biofacies, characteristic of inner shelf Frasnian sequences. My research based on multielement taxonomy and shape analysis of platform elements has drastically revised discrimination of species of Palmatolepis and Ancyrognathus and consequently their stratigraphic ranges. The result is a near doubling in number of zones within the Palmatolepis biofacies, but their resolution is far exceeded by that obtainable through graphic correlation. Correlation between the Palmatolepis and Polygnathus biofacies remains difficult, but is probably resolvable through graphic methods. Proposed research will rigorously test these new biostratigraphic and taxonomic results in widely scattered localities throughout the Devonian tropics, with the additional long-range purpose of developing a comprehensive analysis of Frasnian conodont paleogeography.