歪尾，又稱歪形尾，魚類的一種尾鰭，常見於鯊類和鱘類，歪尾外形和內部結構均不對稱。
外觀：歪尾上葉較大，向背側延伸，下葉較小，不延伸.內部結構：歪尾的鰭片內均有骨骼支持，但不對稱.上葉內有尾椎骨、尾上骨及尾下骨支持，下葉僅有尾下骨支持.歪尾的尾柄細長，能強有力地擺動尾鰭，故鯊類和鱘類是善於快速游泳的魚類.GOOGLE英文翻譯:Also known as the crooked-shaped tail. A kind of tail fins of fish commonly found in sharks and sturgeons. Crooked tail shape and internal structure are asymmetrical. Appearance: crooked tail lobe large, extending to the dorsal, lower lobe small, does not extend . Internal structure: crooked tail fins were bones inside the support, but asymmetric. on the leaves of a tail vertebrae, the tail bone and tail bone under the support of only the end of the next lower lobe of bone support. crooked tail slender caudal peduncle can be a powerful swing tail fins, so shark class and the class is good at fast-swimming sturgeon fish.
