鱼儿就要游，鸟儿就要飞。但是新的研究证实，至少有一种鱼类能行走。非洲肺鱼( Protopterus annectens ) 是存在了2.3亿年的古老物种，它们生活在非洲西部及中部的溪流或湖泊，有很长及呈丝状的鳍。长期以来都有传言说这种鱼能沿着河床行走。现在研究者用摄影机拍到了这种生物在实验室水箱里行走的镜头。
12月12日发布于《国家科学院院刊》（PNAS）的这项研究 中，美国芝加哥大学个体生物学和解剖部的研究者希瑟.金（Heather King）和同事发现，当非洲肺鱼缓步走过水箱地面时，它们使用的是一套以腹鳍驱动、类似四足动物步态的行走方式，将自己的身体撑离了地面，这通常是只有4足陆地动物才会做的事情。
泥盆纪时从肉鳍鱼（sarcopterygian fish ）演化而来的四足动物，是首批统治了陆地的脊椎动物。非洲肺鱼和陆地动物的祖先是近亲，研究者表示，非洲肺鱼用自己的鳍走路，这可能有助于揭示我们的远亲从水里到陆地时经历了什么。
研究小组猜测，相对于游泳，行走可能不太容易吸引捕食非洲肺鱼的生物，也不容易惊吓到非洲肺鱼的猎物。能行走这个本领甚至可能在生物从海洋搬到干燥陆地上生活之前就已经演化出来。希瑟.金表示，或许鱼鳍在演化为专门的肢体之前就已经用来行走了。
Ancient Fish Takes a Walk
Behavioral evidence for the evolution of walking and bounding before terrestriality in sarcopterygian fishes
Heather M. King, Neil H. Shubin, Michael I. Coates and Melina E. Hale
Tetrapods evolved from sarcopterygian fishes in the Devonian and were the first vertebrates to colonize land. The locomotor component of this transition can be divided into four major events: terrestriality, the origins of digited limbs, solid substrate-based locomotion, and alternating gaits that use pelvic appendages as major propulsors. As the sister group to tetrapods, lungfish are a morphologically and phylogenetically relevant sarcopterygian taxon for understanding the order in which these events occurred. We found that a species of African lungfish (Protopterus annectens) uses a range of pelvic fin-driven, tetrapod-like gaits, including walking and bounding, in an aquatic environment, despite having a derived limb endoskeleton and primitively small, muscularly supported pelvis. Surprisingly, given these morphological traits, P. annectens also lifts its body clear of the substrate using its pelvic fins, an ability thought to be a tetrapod innovation. Our findings suggest that some fundamental features of tetrapod locomotion, including pelvic limb gait patterns and substrate association, probably arose in sarcopterygians before the origin of digited limbs or terrestriality. It follows that the attribution of some of the nondigited Devonian fossil trackways to limbed tetrapods may need to be revisited.
