二叠纪末期距今已有约2.5亿年，发生了有史以来最严重的大灭绝事件，地球上大约有96%的物种灭绝，占领海洋近3亿年的主要生物衰败并消亡，新生物开始出现，地球生态系统发生彻底更新。如今，研究人员在日前在线出版的《自然—地球科学》期刊上报告，由海绵和微生物构成的暗礁出现在这次大灭绝之后的150万年。此前的研究认为，由动物遗体构成的暗礁在大灭绝之后的第一个500万年内就已经消失了。
Arnaud Brayard和同事报告了采集自美国犹他州和内华达州的化石，认为这些化石是由海绵和微生物群落组成的暗礁。他们在暗礁沉积物中发现各种各样的软体动物、海胆脊椎和已灭绝的头足纲软体动物菊石。他们指出，暗礁中的这些沉积物应该形成于大灭绝之后150万年内，含有这一时期海底栖息动物的丰富记录。以前的研究认为，这一时间没有海底栖息动物。(生物谷 Bioon.com)
doi:10.1038/ngeo1264
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Transient metazoan reefs in the aftermath of the end-Permian mass extinction
Arnaud Brayard, Emmanuelle Vennin, Nicolas Olivier, Kevin G. Bylund, Jim Jenks, Daniel A. Stephen, Hugo Bucher, Richard Hofmann, Nicolas Goudemand & Gilles Escarguel
Recovery from the devastating Permian–Triassic mass extinction about 252 million years ago is usually assumed to have spanned the entire 5 million years of the Early Triassic epoch. The post-crisis interval was characterized by large-scale fluctuations of the global carbon cycle and harsh marine conditions, including a combination of ocean acidification, euxinia, and fluctuating productivity. During this interval, metazoan-dominated reefs are thought to have been replaced by microbial deposits that are considered the hallmark of the Early Triassic. Here we use field and microscopic investigations to document Early Triassic bioaccumulations and reefs from the western USA that comprise of various sponges and serpulids associated with microbialites and other eukaryotic benthic organisms. These metazoan-rich reefs were formed only 1.5 million years after the extinction, in contrast to previous suggestions of a much delayed recovery of complex benthic communities. We conclude that the predominance of microbial reefs following the mass extinction is restricted to short intervals of the earliest Triassic. We suggest that metazoan reef building continued throughout the Early Triassic wherever permitted by environmental conditions.
