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

贝壳和韧带微结构：对双壳类（软体动物）进化的多分支和平流研究的意义

• 批准号: 9205263
• 负责人: Joseph Carter
• 金额: $ 9.5万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-06-15 至 1995-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9205263&HistoricalAwards=false
• 关键词: Shell; Ligament; Microstructures; Significance; Polythetic

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.

贝壳结构和韧带结构历来是双壳动物系统发育和分类研究的重要组成部分。然而，正如Waller(1990)和Carter(1990a)最近重新定义的那样，韧带结构对于许多灭绝和现存的双壳类仍然知之甚少，而贝壳微结构的数据已经落后于比较解剖学的其他方面，这是因为持续存在不充分的描述性命名，古生代和中生代科的数据缺乏，以及缺乏准确的，关于进化路径和趋同的全面视角。Carter(1990a)最近证明，新的古齿亚纲、翼亚纲和等纤鳃亚纲的数据可以为研究家族和更高层次的进化关系提供重要的新见解。拟议中的研究将把这个数据库扩展到包括剩余的双壳亚纲异形甲纲和双壳亚纲，它将使用双壳纲的整个数据库，结合已发表的和新的贝壳形态、铰齿、贝壳肌肉、鳃、触须、脚和胃结构的数据，以及所有其他相关的硬解剖和软解剖方面的数据，以提供对整个纲的第一个真正全面的家族分支分析。分支系统分析将使用两个可供选择的微型计算机程序和一个混合程序，前者具有寻找简约分支图的有效例程，后者将结合传统分支学和地层学的一些突出点，目前正在开发中。将从传统地层学的角度对相互竞争的节俭分支图进行评估。除了为贝壳、韧带微结构和韧带结构的进化趋同提供新的视角外，这项研究还有望解决双壳类进化的许多重要但以前难以解决的问题，包括双壳类贝壳微结构的早期多样化，Veneroidae瓷器结构的起源，Crassatelloidae的可能分支起源，肌样超家族的起源，以及编织线的瓷器微结构和不对称韧带的演化。此外，这项研究将为未来较低水平的分类研究提供一个完善的系统发育和分类框架，并为更广泛的进化辐射和灭绝研究奠定基础。