Paleoecological study on the recovery and adaptive radiation of benthic invertebrate faunas after the mass extinctions

大规模灭绝后底栖无脊椎动物群的恢复和适应性辐射的古生态学研究

基本信息

批准号：
13440153
负责人：
OJI Tatsuo
金额：
$ 3.39万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

In order to clarify how the benthic organisms recovered and how the new taxonomic groups appeared after the mass extinctions, paleoecological work has been done on the two case studies, one after the P-T, and the other after the end-Cretaceous mass extinctions. Up to now, following results have been obtained.1.In order to measure the diversity change of benthic faunas before the P-T mass extinction, trace fossils in the Late Permian (Changsingian) offshore fades of Kitakami Mountains in northern Japan were examined. As a result, it was suggested that the diversity of benthic faunas had already been low prior to the P-T boundary.2.In order to clarify the diversity recovery of benthic faunas in the Early Triassic, siliciclastic fades of Kitakami Mountains were examined. The Smithian fauna from this fades showed pandemic but low-diversity community, and this Japanese example has predated other occurrences of similar fauna from north America and south Asia.It is important to know the long- … More tern predator-prey interaction, especially when and how strong durophagous predators appeared.We surveyed 21 formations (9 Mesozoic and 12 Cenozoic formations) consisting of shallow-water deposits in Japan to detect whether these formations contain angular-shaped fragments of bivalves and gastropods. Mesozoic formations rarely contained such angular fragments of bivalves and gastropods, and only one example containing such angular fragments was observed from the late Cretaceous. On the other hand, there were abundant angular shell fragments from the Cenozoic formations. We also conducted experiments of mechanical abrasion of shells by using a tumbling barrel, in order to see if such mechanical damage would produce angular shell fragments, the kind we see in the shallow-water deposits. The results of tumbling barrel showed that such abraded shells never show angularly broken shapes. As a result of the field survey and the tumbling experiments, it has been clarified that the angular shell fragments were produced by durophagous predators, and such predatory activity has become intensified since the beginning of the Cenozoic, after the K-T mass extinction. Less

为了阐明大灭绝之后底栖生物是如何恢复的以及新的分类群是如何出现的，对两个案例研究进行了古生态学工作，一个是在P-T之后，另一个是在白垩纪末大灭绝之后。目前已取得以下成果： 1.为了测量P-T大灭绝前底栖动物群的多样性变化，晚二叠世（长辛期）近海遗迹化石逐渐消失对日本北部北上山脉进行了考察，结果表明，在P-T边界之前，底栖动物群的多样性已经很低。2.为了阐明早三叠世底栖动物群的多样性恢复情况，硅质碎屑逐渐消失。对北上山脉的史密斯动物群进行了检查，显示出流行但多样性低的群落，并且这个日本例子早于北美和南部的其他类似动物群的出现。亚洲。了解长期燕鸥捕食者与被捕食者之间的相互作用非常重要，特别是硬食性捕食者出现的时间和程度。我们调查了日本浅水沉积物组成的 21 个地层（9 个中生代地层和 12 个新生代地层），以检测是否存在这些地层含有双壳类和腹足类的角形碎片，中生代地层很少含有这种双壳类和腹足类的角形碎片，而且只有一个。在白垩纪晚期就观察到了含有这种角状碎片的例子。另一方面，我们还利用滚桶进行了贝壳的机械磨损实验，以了解是否存在这种机械磨损。损坏会产生有角的贝壳碎片，就是我们在浅水沉积物中看到的那种。翻滚桶的结果表明，这种磨损的贝壳不会出现有角的破碎形状。通过实地调查和翻滚实验，已明确这些角壳碎片是由硬食性捕食者产生的，并且这种捕食活动自新生代开始、K-T大灭绝之后就变得更加激烈。