Hemigrammus xaveriellus sp. nov., is described from the upper Río Vaupés basin (Amazon basin), Departamento Guaviare, Colombia. It is distinguished from all congeners, except Hemigrammus ataktos, by presenting a conspicuous dark longitudinal midlateral stripe extending along the body. It can be distinguished from this species (and from most congeners) by presenting a conspicuous rounded, horizontally-elongated humeral blotch anterior to the beginning of the dark midlateral stripe, 7 scales rows between dorsal-fin and lateral line (vs. 5-6), and 5 scale rows between lateral line and pelvic-fin insertion (vs. 3-4). The single mature male of H. xaveriellus available possess a well-developed urogenital papilla, a very unusual feature among characids. A discussion on the presence of an enlarged urogenital papilla in the family, as well as comments regarding the putative relationships of the new species, are presented. This article is protected by copyright. All rights reserved.

中文翻译：

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来自哥伦比亚 Río Vaupés 上游的新 Hemigrammus（Characiformes：Characidae），讨论了该家族中是否存在增大的泌尿生殖乳头

Hemigrammus xaveriellus sp. 11 月，来自哥伦比亚瓜维亚雷省的上游 Río Vaupés 盆地（亚马逊盆地）。它与除 Hemigrammus ataktos 之外的所有同类物不同，呈现出沿身体延伸的显眼的深色纵向中侧条纹。它可以与本种（和大多数同类）区分开来，在深色中侧条纹开始前呈现明显的圆形、水平伸长的肱骨斑点，背鳍和侧线之间有 7 排鳞片（vs. 5-6 )，以及侧线和腹鳍插入点之间的 5 排鳞片（对比 3-4）。H. xaveriellus 的单一成熟雄性具有发育良好的泌尿生殖乳头，这是characids 中非常不寻常的特征。关于家族中存在增大的泌尿生殖乳头的讨论，以及关于新物种的假定关系的评论。本文受版权保护。版权所有。