Shen Bing, Dong Lin, Xiao Shuhai, Kowalewski Michal
Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Science. 2008 Jan 4;319(5859):81-4. doi: 10.1126/science.1150279.
Ediacara fossils [575 to 542 million years ago (Ma)] represent Earth's oldest known complex macroscopic life forms, but their morphological history is poorly understood. A comprehensive quantitative analysis of these fossils indicates that the oldest Ediacara assemblage-the Avalon assemblage (575 to 565 Ma)-already encompassed the full range of Ediacara morphospace. A comparable morphospace range was occupied by the subsequent White Sea (560 to 550 Ma) and Nama (550 to 542 Ma) assemblages, although it was populated differently. In contrast, taxonomic richness increased in the White Sea assemblage and declined in the Nama assemblage. These diversity changes, occurring while morphospace range remained relatively constant, led to inverse shifts in morphological variance. The Avalon morphospace expansion mirrors the Cambrian explosion, and both events may reflect similar underlying mechanisms.
埃迪卡拉化石（距今5.75亿至5.42亿年前）代表了地球上已知最古老的复杂宏观生命形式，但人们对它们的形态演化历史了解甚少。对这些化石进行的全面定量分析表明，最古老的埃迪卡拉生物群——阿瓦隆生物群（距今5.75亿至5.65亿年前）——已经涵盖了埃迪卡拉形态空间的全部范围。随后的白海生物群（距今5.6亿至5.5亿年前）和纳马生物群（距今5.5亿至5.42亿年前）占据了类似的形态空间范围，尽管生物组成有所不同。相比之下，白海生物群的分类丰富度增加，而纳马生物群的分类丰富度下降。在形态空间范围相对保持不变的情况下发生的这些多样性变化，导致了形态方差的反向变化。阿瓦隆形态空间的扩张反映了寒武纪大爆发，这两个事件可能反映了相似的潜在机制。
