Any of numerous extinct colonial marine animals chiefly of the orders Dendroidea and Graptoloidea of the late Cambrian to the early Mississippian periods, whose fossil remains are often used to date the rocks of the Silurian and Ordovician ages.是什么意思_Any of numerous extinct colonial marine animals chiefly of the orders Dendroidea and Graptoloidea of the late Cambrian to the early Mississippian periods, whose fossil remains are often used to date the rocks of the Silurian and Ordovician ages.在线翻译_英语_读音_用法_例句