大颚细锯脂鲤，为辐鳍鱼纲脂鲤目脂鲤科的其中一个种。

本鱼分布于南美洲圭亚那、法属圭亚那、巴西及委内瑞拉的溪流中。

X-ray fish, the only species in the genus Pristella, is commonly known as the X-ray fish or X-ray tetra because of its highly transparent body. It is a widely distributed and adaptable fish, being found in the Amazon and Orinoco basins, as well as coastal rivers in the Guianas in both acidic and alkaline waters. Unlike most other characins, it is tolerant of (and sometimes found in) slightly brackish water. It is small (up to around 5 cm or 2.0 in in length) and lives in large groups, and males can be distinguished from females by being smaller and thinner than the females. Like most other tetras, it feeds primarily on small insects and planktonic animals.