1. small (2 in) extinct eellike fish with a finned tail and a notochord and having cone-shaped teeth containing cellular bone; late Cambrian to late Triassic; possible predecessor of the cyclostomes. 
   2英寸大小已经灭绝的长有带鳍尾、脊索和含有细胞质状骨胳的锥形牙齿似鳗的鱼；后寒武纪到后三叠纪的生物；可能是圆口纲脊椎动物的祖先。
2. Of, belonging to, or being the oldest and largest division of geologic time, preceding the Cambrian Period, often subdivided into the Archeozoic and Proterozoic eras, and characterized by the appearance of primitive forms of life. 
   前寒武纪的地质年代中最古老和最大的阶段的、属于这一阶段的或处于这一阶段的，其前为寒武纪期，寒武纪期又可细分为始生代和原生代，特征为原始生命形式的出现
3. Of, belonging to, or designating the era of geologic time that includes the Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian periods and is characterized by the appearance of marine invertebrates, primitive fishes, land plants, and primitive reptiles. 
   古生代的地质时代的一个时期的，属于这个时期的或这么称呼的，包括寒武纪、奥陶纪、志留纪、泥盆纪、密西西比纪、宾夕法尼亚纪和二叠纪时期，并且以海洋无脊椎动物、原始鱼类、陆地植物和早期爬行动物的出现为特征
4. 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. 
   笔石动物许多已绝灭的殖民地海洋生物中的任何一种，主要为寒武纪晚期到密西西比纪早期的树形笔石目及笔石纲的生物，其化石残存物常用于确定志留纪和奥陶纪岩石的年代

查看更多例句 相关情景会话