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。