EVOLUTIONARY PALEOBIOLOGY OF CHAMBERED CEPHALOPDS

对现代和化石有室头足类动物的进化古生物学方面进行了分析，特别提到了菊石和现代鹦鹉螺。结果，下列证据得到了明确：1。对北海道白垩纪菊石中多种菊石的呕吐壳形态分析表明，菊石中存在多种多样的流化适应性设计。通过与其它软体动物胚壳的微点缀对比SEM观察，推断了菊石幼壳（ammonitellas）的胚源。通过对化石发生方式的仔细观察，考虑了北海道上白垩统菊石死亡组合的埋藏过程。通过对菊石颌器与现代鹦鹉螺的比较解剖，探讨了菊石的摄食习性。以菲律宾和斐济的鹦鹉螺（Nautilus pompilius）标本为基础，分析了鹦鹉螺（Nautilus pompilius）软硬组织的形态变异，并对其进化和生态学意义进行了探讨。

Evolutionary paleobiological, aspects of modern and fossil chambered cephalopods were analyzed, with special reference to ammonites and modern Nautilus. As a result, the following lines of evidence were made clear.1. Wide variety of adaptive design for streamling among Cretaceous ammonites was suggested from vomparative shell shape analysis of many species from Hokkaido.2. Embryonic origin of ammonite juvenile shells (ammonitellas) was inferred from comparative SEM observation of microornament with other molluscan embryonic shells.3. Taphonomic process of ammonite death assemblages in the Upper Cretaceous of Hokkaido was considered from careful observation of mode of fossil occurrence.4. Feeding habits of ammonites were considered on the basis of comparative anatomy of jaw apparatuses of ammonites and modern Nautilus.5. Morphologic variation of soft and haed tissues in Nautilus pompilius was analyzed on the basis of specimens from the Philippines and Fiji, and its evolutionary and ecological implications were considered.