Johnson G David, Ida Hitoshi, Sakaue Jiro, Sado Tetsuya, Asahida Takashi, Miya Masaki
Division of Fishes, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA.
Proc Biol Sci. 2012 Mar 7;279(1730):934-43. doi: 10.1098/rspb.2011.1289. Epub 2011 Aug 17.
We report the discovery of an enigmatic, small eel-like fish from a 35 m-deep fringing-reef cave in the western Pacific Ocean Republic of Palau that exhibits an unusual suite of morphological characters. Many of these uniquely characterize the Recent members of the 19 families comprising the elopomorph order Anguilliformes, the true eels. Others are found among anguilliforms only in the Cretaceous fossils, and still others are primitive with respect to both Recent and fossil eels. Thus, morphological evidence explicitly places it as the most basal lineage (i.e. the sister group of extant anguilliforms). Phylogenetic analysis and divergence time estimation based on whole mitogenome sequences from various actinopterygians, including representatives of all eel families, demonstrate that this fish represents one of the most basal, independent lineages of the true eels, with a long evolutionary history comparable to that of the entire Anguilliformes (approx. 200 Myr). Such a long, independent evolutionary history dating back to the early Mesozoic and a retention of primitive morphological features (e.g. the presence of a premaxilla, metapterygoid, free symplectic, gill rakers, pseudobranch and distinct caudal fin rays) warrant recognition of this species as a 'living fossil' of the true eels, herein described as Protanguilla palau genus et species nov. in the new family Protanguillidae.
我们报告了在西太平洋帕劳共和国一个35米深的边缘礁洞穴中发现的一种神秘的、类似小鳗鱼的鱼类，它展现出一系列不同寻常的形态特征。其中许多特征独特地刻画了包括真正鳗鱼在内的鳗形目19个科的现存成员。其他一些特征仅在白垩纪化石中的鳗形目鱼类中发现，还有一些特征相对于现存和化石鳗鱼来说都是原始的。因此，形态学证据明确将其置于最基部的谱系（即现存鳗形目的姐妹群）。基于各种辐鳍鱼类（包括所有鳗鱼科的代表）的全线粒体基因组序列进行的系统发育分析和分歧时间估计表明，这种鱼代表了真正鳗鱼最基部、独立的谱系之一，其漫长的进化历史与整个鳗形目相当（约2亿年）。如此漫长、独立且可追溯到中生代早期的进化历史，以及对原始形态特征的保留（例如存在前颌骨、后鳍基骨、游离的续骨、鳃耙、伪鳃和明显的尾鳍条），使得该物种有理由被认定为真正鳗鱼的“活化石”，在此将其描述为新科原鳗科中的原鳗属帕劳原鳗种（Protanguilla palau），属及种均为新种。
