Onychogomphus uncatus (Large pincertail), like its slightly smaller relative O. forcipatus (Small Pincertail), is a yellow-and-black clubtail with large terminal appendages. Mature imagos have blue eyes, a treat they share with south-western Small Pincertails (subspecies unguiculatus), but can be distinguished from the latter by the larger black markings on lateral sides of the thorax and ante-humeral markings. A third species Large Pincertail can be confused with, though with a very limited area of occurrence, is Cazuma Pincertail (O. cazuma). This species looks like a mix of Small and Large Pincertail.
The geographical range of Large Pincertails encompasses south-western Europe (Iberia, France, Italy) and northern Africa. They inhabit clear flowing streams in rocky areas.