either of a pair of fins situated just behind the head in fishes that help control the direction of movement
例句
用作名词 (n.)
Winglike pectoral fins extend along the sides of the head. 翼状的胸鳍沿头的两侧延伸生长。
Oddly enough, this ventilation shift may have kicked off the gradual morphing of the shoulder girdle and pectoral fins. 奇怪的是,这呼吸上的改变有可能启动了前肢带与胸鳍的形态逐渐改变。