Phylogenetic Relationships Among Spire-bearing Articulate Brachiopods

腕足动物是迷人的，但知之甚少的双壳类 海洋动物 它们看起来很像蛤蜊，至少外表上是这样， 但在家谱上只是远亲 甚至 虽然腕足动物在沿着并不常见， 除了在新西兰和澳大利亚的部分地区，它们很常见， 在2.5亿年前的古生代， 古生代海洋生物群的重要组成部分。 基于这个理由， 古生物学家有兴趣了解他们的 生态学、形态学、生长和行为，以及它们的时间和 地理分布，部分原因是为了了解它们的下降， 濒临灭绝 桑德拉·卡尔森博士， 加州戴维斯分校正在研究 腕足动物，那些轴承独特的结构内， 阀门看起来很像两个锥形弹簧， 参与获取食物和氧气， 行为。 目前对这些生物的分类表明， 这些结构只进化了一次，但是 卡尔森博士表示，情况不太可能如此。 如果塔尖- 腕足动物已经进化了好几次， 在一个单一的分类群中混淆了它们的进化 历史和制约因素对生态因素的影响， 螺旋进化 研究其他形态特征的 化石和现存生物将有助于改进分类 和腕足动物的生殖，并帮助了解他们的 古生代的地质升降

Brachiopods are fascinating but poorly understood bivalved marine animals. They look similar to clams, at least externally, but are only distantly related in a genealogical sense. Even though brachiopods are not commonly found along seashores today, except in parts of New Zealand and Australia, they were common and diverse over 250 million years ago in the Paleozoic Era and were important elements of the Paleozoic marine biota. For this reason, paleontologists are interested in learning about aspects of their ecology, morphology, growth and behavior, and their temporal and geographic distribution, in part to understand their decline and near extinction. Dr. Sandra Carlson of the University of California at Davis is studying the spire-bearing articulate brachiopods, those bearing distinctive structures inside their valves that look much like two cone-shaped springs and that are involved in obtaining food and oxygen and in reproductive behaviors. The current classification of these organisms suggests that these structures have evolved only once, but preliminary work by Dr. Carlson indicates that is not likely the case. If spire- bearing brachiopods have evolved several times, then placing them together in a single taxonomic group confuses their evolutionary history and constrains work on ecological factors responsible for spire evolution. Study of other morphological features of the fossil and extant organisms will help improve the classification and phylogeny of brachiopods, and help in understanding their geological rise and fall in the Paleozoic.