Adaptive radiation of the early evolution of ichthyosaurs

过去三年的工作重点是加拿大不列颠哥伦比亚省东北部三叠纪岩石中极其丰富的海洋爬行动物化石群。该地区有超过1200米的连续三叠纪海洋沉积，跨越早、中、晚三叠世。三叠纪时期，四足动物首次回归海洋并在海洋领域实现多样化。因此，它是海洋爬行动物研究中尤为重要的时间间隔。这项研究涉及新化石材料的收集和制备，以及其他机构关键收藏品的比较研究。我们的工作主要集中在两个层位——马鹿湖的下三叠统硫磺山地层，以及粉红山地区的上三叠统 Pardonet 地层。这笔赠款的总体成果是广泛的。收集了 140 多个脊椎动物化石标本，目前正在准备和研究中。其中之一是 23m 长的鱼龙，它是化石记录中已知的最大的海洋爬行动物。关于这项工作的两篇科学论文已经发表（Motani 等人，1998 年；Nicholls 和 Manabe，1998 年）。两篇论文已在专业会议上发表（Nicholls 和 Manabe，1999a，1999b）。另外五篇科学论文正在进行中，并将随着样本研究和准备的进行而产生。

Work for the past three years has focused on the incredibly rich fossil faunas of marine reptiles in the Triassic rocks of northeastern British Columbia, Canada. This region has over 1200 m of continuous Triassic marine sedimentation, spanning the Early, Middle and Late Triassic. It is during the Triassic that tetrapods first returned to the sea and diversified in the marine realm. Consequently, it is a particularly important time interval in the study of marine reptiles. This study has involved the collection and preparation of new fossil material, and the comparative study of critical collections in other institutions. Our work was concentrated primarily in two horizons - the Lower and Middle Triassic Sulphur Mountain Formation at Wapiti Lake, and the Upper Triassic Pardonet Formation in the Pink Mountain area. The overall results of this grant have been extensive. Over 140 fossil vertebrate specimens were collected, which are being prepared and studied. One of these, a 23m ichthyosaur, is the largest marine reptile known in the fossil record. Two scientific papers on this work have already been published (Motani et al, 1998 ; Nicholls and Manabe, 1998). Two papers have been presented at professional meetings (Nicholls and Manabe, 1999a, 1999b). Five more scientific papers are in progress, and will result as study and preparation of the specimens proceeds.