A regional stage (453–449 Ma ago) of the Late Ordovician in the Upper Caradoc, underlain by the Actonian and overlain by the Pusgillian.
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。