Bernardi G, Powers D A
Hopkins Marine Station, Stanford University, Department of Biological Sciences, Pacific Grove, California 93950.
Mol Phylogenet Evol. 1992 Jun;1(2):161-7. doi: 10.1016/1055-7903(92)90027-e.
The classification of the sharks is unclear. This is particularly true for the superorder Squalomorphii. The relationships between the squalomorphs and other superorders of sharks and the relationships between the different orders within the squalomorphs are a matter of debate. Here, we report a molecular phylogeny for a little known member of this superorder, the genus Echinorhinus. Echinorhinus is most commonly classified in either the family Echinorhinidae (Squaliformes) or the family Squalidae (Squaliformes). However, some authors have suggested a closer relationship to the order Hexanchiformes. In an attempt to shed light on this controversy, we have cloned, sequenced, and compared two genes widely used in molecular phylogeny studies, the cytochrome b and the 18S rRNA from the rare prickly shark, Echinorhinus cookei, and two potential relatives, the spiny dogfish Squalus acanthias (Squaliformes), and the sevengill shark, Notorynchus cepedianus (Hexanchiformes). The sequences of these genes for the prickly shark, the dogfish, and the sevengill shark were found to be equally divergent, suggesting that the prickly shark is no closer to the order Squaliformes than to the order Hexanchiformes.
鲨鱼的分类尚不明确。对于鲨总目来说尤其如此。鲨总目与其他鲨鱼总目的关系以及鲨总目内部不同目之间的关系存在争议。在此，我们报告了鲨总目中一个鲜为人知的成员——棘鲨属的分子系统发育情况。棘鲨最常被归类于棘鲨科（角鲨目）或真鲨科（角鲨目）。然而，一些作者认为它与六鳃鲨目关系更近。为了阐明这一争议，我们克隆、测序并比较了分子系统发育研究中广泛使用的两个基因，即来自稀有刺鲨（Echinorhinus cookei）的细胞色素b和18S rRNA，以及两个可能的亲属，即白斑角鲨（Squalus acanthias，角鲨目）和六鳃鲨（Notorynchus cepedianus，六鳃鲨目）。结果发现，刺鲨、角鲨和六鳃鲨的这些基因序列差异程度相同，这表明刺鲨与角鲨目的关系并不比与六鳃鲨目的关系更近。
