Early Evolution of Ligaments and Shell Microstructure in the Bivalvia, with a Comprehensive, Polythetic, Phylogenetic Analysis

双壳类韧带和贝壳微结构的早期进化及综合系统发育分析。虽然韧带和贝壳微结构是双壳纲系统发育信息的重要来源，但对于大多数早、中古生代的属和种来说，这些特征仍然知之甚少。最近在肯塔基州的奥陶纪双壳类和哥特兰的志留纪双壳类中发现了残留的文石韧带和贝壳微结构，这表明这些特征可能在显生界都可以追溯到。这项资助的研究将开发一个广泛的古生代双壳韧带和贝壳微结构数据库，重点是选定的古生代动物群，代表美国、加拿大北极、瑞典、撒丁岛、捷克共和国、中国、澳大利亚、新西兰和南极洲的地点。然后，这些数据将与其他古生物数据和有限的软解剖学推断相结合，根据简约法、似然法和距离法提供一系列全面的、严格的古生代双壳类系统发育分析，并对照地层数据、传统进化系统学和现代分子系统学进行测试。最终的系统发育综合将用于修订古生代双壳类的系统发育分类。除了阐明早期双壳类韧带和贝壳微结构的演化外，本研究还将有助于解决双壳类进化的许多悬而未决的问题，并将为未来后古生代双壳类的系统发育分析提供坚实的基础。

ABSTRACTEarly Evolution of Ligaments and Shell Microstructure in the Bivalvia, with a Comprehensive, Polythetic, Phylogenetic AnalysisDr. Joseph G. Carter, University of North Carolina at Chapel Hill Although ligaments and shell microstructures are important sources of phylogenetic information for the Bivalvia, these features remain poorly known for most early and middle Paleozoic genera and species. The recent discovery of relict aragonitic ligaments and shell microstructures in Ordovician bivalves from Kentucky and in Silurian bivalves from Gotland suggests that these features may be traceable throughout the Phanerozoic. The funded research will develop an extensive database of Paleozoic bivalvian ligament and shell microstructure, focusing on selected Paleozoic faunas representing localities in the United States, Arctic Canada, Sweden, Sardinia, the Czech Republic, China, Australia, New Zealand, and Antarctica. These data will then be combined with other paleontological data and limited inferences of soft anatomy to provide a series of taxonomically comprehensive, rigorously phylogenetic analyses of Paleozoic bivalves based on parsimony, likelihood, and distance methods, tested against stratigraphic data, traditional evolutionary systematics, and modern molecular phylogenies. The final phylogenetic synthesis will be used for a revised phylogenetic classification of Paleozoic bivalves. In addition to clarifying the early evolution of ligaments and shell microstructures, this research will help resolve many outstanding questions of bivalve evolution, and will provide a firm foundation for future phylogenetic analyses of post-Paleozoic bivalves.