A N. American stage (299–280 Ma ago) in the Early Permian epoch, underlain by the Virgilian (Pennsylvanian), overlain by the Leonardian, and roughly contemporaneous with the Asselian and lower Sakmarian stages.
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。