ABSTRACT. “Apteronotus” bonapartii (Castelnau 1855) was described based on a single specimen caught in a lake draining into the Río Ucayali, Perú, and is now reported from several rivers in South America. Because the generic placement of this species is currently uncertain, in this paper we use the genus name “Apteronotus” within quotes for reference to “Apteronotus” bonapartii (Castelnau, 1855) and “A.” apurensis Fernández-Yépez, 1968; we use the genus name without quotes for the more precise usage referring to a putatively monophyletic group including the type species (A. albifrons). “Apteronotus” bonapartii has a laterally compressed body, subterminal mouth with the rictus passing the eyes and teeth present in both jaws. The species has been differentiated from others placed in the genus by the low number of scale rows (5–8) above the lateral line. There is substantial intraspecific variation among specimens, in part associated with pronounced sexual dimorphism in head shape. We describe aspects of the morphology and cranial osteology of 52 specimens of “A.” bonapartii from Central Amazon and 12 specimens from other localities in the Amazon and Orinoco basins including the holotype from Río Ucayali. Males have slightly longer facial dimensions than females, and the holotype appears to fit on the male growth trajectory. Specimens from Napo, Metica, Orituco and Apure rivers are similar to specimens from the Central Amazon and the holotype. There is sexual dimorphism in the structure of the lower jaw, including its overall shape and profile (e.g., smooth curve of the dentary in males vs. a straight edge of the dentary in females), but no sexual dimorphism of teeth was noted. The postarticular portion of the lower jaw is formed equally by the anguloarticular and retroarticular. There is individual variation in the ossification of pharyngobranchial 4 and hypobranchial 4. We found no morphological differences between specimens of “A.” bonapartii from the Río Apure and the species described as “A.” apurensis Fernández-Yépez 1968.

中文翻译：

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“Apteronotus”bonapartii (Castelnau, 1855) 的身份，一种来自亚马逊的两性异形的南美刀鱼，并附有关于其颅骨骨学和“Apteronotus” apurensis Fernández-Yépez, 1968 (Gymnotiformes, Apteronotidae) 的说明

摘要。“Apteronotus”bonapartii (Castelnau 1855) 是根据在流入秘鲁乌卡亚利河的湖泊中捕获的单个标本进行描述的，现在据报道来自南美洲的几条河流。由于该物种的属名目前尚不确定，因此在本文中，我们在引用“Apteronotus”bonapartii (Castelnau, 1855) 和“A”时使用带引号的属名“Apteronotus”。apurensis Fernández-Yépez, 1968; 我们使用不带引号的属名是为了更精确的用法，指的是一个假定的单系群，包括类型物种（A. albifrons）。“Apteronotus”bonapartii 身体侧向压缩，嘴近端，唇齿通过眼睛，两颚的牙齿。该物种与该属中的其他物种的区别在于侧线上方的鳞片行（5-8）数量少。标本之间存在大量种内变异，部分与头部形状的明显性别二态性有关。我们描述了 52 个“A”标本的形态学和颅骨骨学方面。来自亚马逊中部的 bonapartii 和来自亚马逊和奥里诺科盆地其他地区的 12 个标本，包括来自 Río Ucayali 的正模标本。男性的面部尺寸略长于女性，正模模型似乎符合男性的生长轨迹。来自纳波河、梅蒂卡河、奥里图科河和阿普雷河的标本与亚马逊中部的标本和正模标本相似。下颌的结构存在两性异形，包括其整体形状和轮廓（例如，男性牙齿的平滑曲线与女性牙齿的直线边缘），但没有注意到牙齿的性别二形性。下颌的关节后部分由角关节和后关节同样构成。咽部 4 和下鳃 4 的骨化存在个体差异。我们发现“A”的标本之间没有形态学差异。来自 Río Apure 的 bonapartii 和被描述为“A”的物种。apurensis Fernández-Yépez 1968。”来自 Río Apure 的 bonapartii 和被描述为“A”的物种。apurensis Fernández-Yépez 1968。”来自 Río Apure 的 bonapartii 和被描述为“A”的物种。apurensis Fernández-Yépez 1968。