Shell and Ligament Microstructures: Significance for Polythetic Cladistic and Stratophenetic Studies of Bivalve (Molluscan) Evolution

贝壳微观结构和韧带结构在历史上 是中国植物发生学和分类学研究的重要组成部分， 双壳类 然而，最近重新定义的韧带结构 Waller（1990）和Carter（1990a）所提出的，对许多人来说仍然知之甚少。 已灭绝和现存的双壳类，以及贝壳的数据 微观结构落后于其他方面的比较 解剖学，因为一个不充分的描述性的持久性 命名，缺乏古生界和中生界的数据 家庭，以及缺乏准确，全面的观点 关于进化路径和趋同的研究 卡特（1990a）最近 新的数据表明， Pteriomorphic和Isofilibranchia可以提供重要的新的 深入了解家庭和更高层次的进化关系。 拟议的研究将扩展该数据库，以包括 其余的双壳类亚纲异壳纲和异连丝纲，以及 它将使用双壳类的整个数据库， 根据已发表的和新的贝壳形态学数据，铰链齿系， 壳的肌肉组织，鳃，须，足和胃的结构，以及所有 硬和软解剖结构的其他相关方面， 第一次真正全面的，家庭支序分析，这整个 课 分支分析将采用两种替代方法， 微计算机程序与有效的例行程序， 简约的分支图，以及混合程序，目前 Fisher（1991）开发的，它将联合收割机的一些 传统分支系统学和层表型学的要点。 竞争的简约进化枝图将从 传统的地层现象学视角。 除了提供关于进化的新观点外， 壳与韧带的会聚 结构，这项研究有望解决许多重要的，但 以前难以解决的双壳类进化问题，包括 双壳类贝壳微结构的早期变化， 在Veneroida中的瓷器结构的起源，可能的 Crassatelloidea的二系起源，肌样的起源 超家族，以及瓷器显微结构的演变 和不对称韧带的问题 此外，本发明还 这项研究将提供一个健全的系统发育和分类 未来低层次分类学研究的框架，以及 为更广泛地研究进化辐射和灭绝奠定了基础。

Shell microstructure and ligament structures have historically been important components of research on phylogeny and taxonomy in the Bivalvia. However, ligament structures, as recently redefined by Waller (1990) and Carter (1990a), remain poorly known for many extinct as well as extant bivalves, and data of shell microstructure have lagged behind other aspects of comparative anatomy because of the persistence of an inadequate descriptive nomenclature, a paucity of data for Paleozoic and Mesozoic families, and the lack of an accurate, comprehensive perspective on evolutionary pathways and convergence. Carter (1990a) recently demonstrated that new data of subclasses Palaeotaxodonta, Pteriomorphia and Isofilibranchia can provide significant new insights into family and higher level evolutionary relationships. The proposed research will extend this database to include the remaining bivalve subclasses Heteroconchia and Anomalodesmata, and it will use the entire database for the Bivalvia in conjunction with published and new data of shell morphology, hinge dentition, shell musculature, gill, palp, pedal and stomach structure, and all other pertinent aspects of hard and soft anatomy to provide the first truly comprehensive, family-cladistic analysis of this entire class. The cladistic analyses will employ two alternative microcomputer programs with efficient routines for finding parsimonious cladograms, as well as a hybrid program, presently under development by Fisher (1991), which will combine some of the salient points of conventional cladistics and stratophenetics. Competing parsimonious cladograms will be evaluated from the perspective of traditional stratophenetics. In addition to providing new perspectives on evolutionary convergence in shell and ligament microstructure and ligament structure, this research is expected to resolve many important but previously intractable questions of bivalve evolution, including the early diversification of shell microstructure in the Bivalvia, the origin of porcelaneous structures in the Veneroida, possible diphyletic origins of the Crassatelloidea, the origin of the myoid superfamilies, and the evolution of porcelaneous microstructures and asymmetrical ligaments in the Anomalodesmata. Additionally, this research will provide a sound phylogenetic and taxonomic framework for future lower-level taxonomic studies, as well as a basis for broader studies of evolutionary radiation and extinction.