The timescale of animal diversification has been a focus of debate over how evolutionary history should be calibrated to geologic time. Molecular clock analyses have invariably estimated a Cryogenian or Tonian origin of animals while unequivocal animal fossils first occur in the Ediacaran. However, redating of key Ediacaran biotas and the discovery of several Ediacaran crown-Metazoa prompt recalibration of molecular clock analyses. We present revised fossil calibrations and use them in molecular clock analyses estimating the timescale of metazoan evolutionary history. Integrating across uncertainties including phylogenetic relationships, clock model, and calibration strategy, we estimate Metazoa to have originated in the early Ediacaran, Eumetazoa in the middle Ediacaran, and Bilateria in the upper Ediacaran, with many crown-phyla originating across the Ediacaran-Cambrian interval or elsewise fully within the Cambrian. These results are in much closer accord with the fossil record, coinciding with marine oxygenation, but they reject a literal reading of the fossil record.

中文翻译：

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后生动物的埃迪卡拉纪起源和后生动物的埃迪卡拉纪-寒武纪多样化


动物多样化的时间尺度一直是关于进化历史应该如何根据地质时间进行调整的争论的焦点。分子钟分析总是估计动物的低温期或托尼期起源，而明确的动物化石首先出现在埃迪卡拉纪。然而，对关键埃迪卡拉纪生物群的重新测年和几个埃迪卡拉纪冠-后生动物的发现促使重新校准分子钟分析。我们提出了修订后的化石校准，并将其用于分子钟分析，以估计后生动物进化历史的时间尺度。综合包括系统发育关系、时钟模型和校准策略在内的不确定性，我们估计后生动物起源于埃迪卡拉纪早期，真后生动物起源于埃迪卡拉纪中期，双侧动物起源于埃迪卡拉纪上部，许多冠门起源于埃迪卡拉纪-寒武纪间隔，或者完全起源于寒武纪。这些结果与化石记录更一致，与海洋氧化作用相吻合，但他们拒绝对化石记录的字面解读。