Systematics, Ontogeny, Osteology and Historical Biogeography of Paddlefishes (Chondrostei: Polyodontidae)

尽管这个鱼类家族的体型很小，但比较解剖学家和古生物学家对白鲟或多齿鱼科非常感兴趣。这两个现存的物种出现在中国的长江和密西西比河，在北美西部也发现了几个化石分类群。Drs。贝米斯和格兰德正在研究现存物种和化石物种的解剖学，以及生物形态的个体发育，以确定它们的系统发育和历史生物地理学。他们主要关注三个主题：1。化石和现存白鲟的进化关系及其对其他鳍类鱼类研究的意义2. 极端解剖学专门化的起源，如对滤食的修改和对电感受器的细化；和3。白鲟在北美和中国的不间断分布。三个现实因素使研究成为可能和及时：1。最近在怀俄明州的收集工作发现了一系列保存异常完好的白鲟化石；2. 来自蒙大拿的一种新的化石物种已经可以用于分析；和3。由公共鱼类孵化场开发的白鲟养殖方法允许研究大系列的发育阶段。这项对活的和化石形式的全面比较解剖学研究的结果将提高对鳐鱼的进化史的理解，特别是对特殊的白鲟的理解。

Despite the small size of this family of fishes, the paddlefishes or Polyodontidae are of great interest to comparative anatomists and paelontologists. The two living species occur in the Yangtze river of China and in the Mississippi, and several fossil taxa are known from western North America. Drs. Bemis and Grande are studying the anatomy of the living and fossil species as well as the ontogeny of the living forms, to determine their phylogeny and historical biogeography. They are focusing on three major topics: 1. The evolutionary relationships among fossil and living paddlefishes and their significance for studies of other ray-finned fishes; 2. The origin of extreme anatomical specializations, as represented by modifications for filter feeding and elaboration of electoreceptors; and 3. The extraordinary disjunct distribution of paddlefishes in North America and China. Three practical factors make the study possible and timely: 1. Recent collecting efforts in Wyoming have produced a series of unusually well-preserved fossil paddlefishes; 2. A new fossil species from Montana has become available for analysis; and 3. Methods developed by public fish hatcheries for the culture of paddlefish allow the study of large series of developmental stages. Results from this comprehensive comparative anatomical study of living and fossil forms will improve understanding of the evolutionary history of ray-finned fishes in general and of the peculiar paddlefishes in particular.