The Beginning of the Mesozoic: Paleoecological and Paleo- environmental Analysis of the Lower Triassac Virgin Limestones (Nevada and Utah)

二叠纪末期的大规模灭绝被认为是自后生动物生命起源以来地球生物圈经历的最大扰动。 尽管人们对这次大规模灭绝的原因知之甚少，但对于其后果中的生物条件或从该事件中生物恢复的性质知之甚少。 二叠纪结束后 5 分钟沉积的 Moenkopi 组（内华达州南部和犹他州西南部）下三叠世原始部分的化石动物群和石灰岩为了解浅海碳酸盐环境中的底栖动物群在此恢复期的生存状况提供了机会。 对原始石灰岩的初步研究表明，沉积在正常海洋环境中，具有物种丰富度相对较低的底栖大型无脊椎动物组合。 具有潜在重要意义的是表面正常海洋叠层石的间隔，这可能代表由于大规模灭绝造成的食草动物的限制，从边缘海洋保护区暂时扩展到正常海洋环境。 大量最早有关节的海百合标本的存在证明了复苏开始的证据，这些海百合标本是从危机中幸存下来的一些未知的古生代生物进化而来的。 研究将阐明生物群从大规模灭绝中恢复的方式。

The mass extinction at the end of the Permian has been established as the greatest perturbation which the Earth's biosphere has experienced since the origin of metazoan life. Although relatively little is known about the cause of this mass extinction, even less is known on biotic conditions in its aftermath or the nature of biotic recovery from this event. Fossil faunas and limestones in the Lower Triassic Virgin Member of the Moenkopi Formation (southern Nevada and southwestern Utah), deposited 5 my after the end of the Permian, present an opportunity to learn how benthic faunas in shallow marine carbonate environments were faring in this recovery interval. Preliminary study of the Virgin limestones indicates deposition in a normal marine environment with benthic macroinvertebrate assemblages of relatively low species richness. Of potentially great significance are intervals of apparent normal marine stromatolites, which may represent temporary expansion from marginal marine refugia into normal marine settings due to restriction of grazers, caused by the mass extinction. Evidence for the beginning of recovery is demonstrated through the presence of abundant specimens of the earliest articulate crinoid, which had evolved from some unknown Paleozoic inadunate that survived the crisis. Research will illuminate the way in which biotas recover from mass extinctions.