Claeson Kerin M, Bemis William E, Hagadorn James W
Department of Geological Sciences, Jackson School of Geosciences, The University of Texas, Austin, Texas 78712, USA.
J Morphol. 2007 Nov;268(11):1021-39. doi: 10.1002/jmor.10567.
Polypterid fishes are considered the basalmost group of extant actinopterygians and may be a direct link to understanding the systematics and evolution of the first bony fishes. Several investigations have been conducted on one member genus, Polypterus; however, since the first specimens of its sister taxon Erpetoichthys calabaricus were described, remarkably little work has been done on the species. We review terminology critical to understanding cranial morphology in polypterids and present a new description of the skull of E. calabaricus as observed through classical methods of skeletal preparation, X-radiographic microfocus computed tomography, and 3D-digital reconstruction. Differences among E. calabaricus and at least three species of Polypterus (P. bichir, P. senegalus, and P. endlicheri), besides the gross variation in size, include an overall elongation of the skull roof observable in most elements of E. calabaricus with a shortening of most associated processes. In addition, several elements present in species of Polypterus are absent in E. calabaricus. As a result, Polypterus should not be used as a proxy for the family Polypteridae to the exclusion of E. calabaricus in phylogenetic studies, which examine early actinopterygians. Each should be treated separately, to resolve inter- and intrarelationships of Polypteridae.
多鳍鱼被认为是现存辐鳍鱼类中最基部的类群，可能是理解最早的硬骨鱼类系统发育和进化的直接纽带。已经对其一个成员属多鳍鱼属进行了多项研究；然而，自从其姐妹分类单元喀麦隆钝吻肺鱼的首批标本被描述以来，对该物种的研究非常少。我们回顾了理解多鳍鱼颅骨形态学至关重要的术语，并通过骨骼制备的经典方法、X射线微焦点计算机断层扫描和三维数字重建，对喀麦隆钝吻肺鱼的头骨进行了新的描述。喀麦隆钝吻肺鱼与至少三种多鳍鱼（波利氏多鳍鱼、塞内加尔多鳍鱼和恩氏多鳍鱼）之间的差异，除了大小上的总体差异外，还包括在喀麦隆钝吻肺鱼的大多数骨骼元素中可观察到的颅顶整体拉长，以及大多数相关骨骼突起的缩短。此外，喀麦隆钝吻肺鱼没有多鳍鱼物种中存在的几种骨骼元素。因此，在研究早期辐鳍鱼类的系统发育研究中，不应将多鳍鱼用作多鳍鱼科的代表而排除喀麦隆钝吻肺鱼。在解决多鳍鱼科的科间和科内关系时，应分别对待它们。
