The earliest stage in the Devonian period, preceded by the Late Silurian, followed by the Praghian, and dated at 416–411.2 Ma ago (Int. Commission on Stratigraphy, 2004).
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。