There are three different species of Hump-nosed Viper in Sri Lanka, Hypnale hypnale, H. nepa, and H. zara which all contribute to morbidity on the island. H. nepa can be distinguished from H. hypnale and H. zara by the presence of a wart-like protuberance at the tip of the snout. H. zara can be distinguished from H. nepa and H. hypnale by its distinctly elevated snout and several other scale characteristics.

The Hypnale sp. are pit vipers with many color morphs. Species of Hypnale are restricted to Southern India and Sri Lanka. H. nepa and H. zara are endemic to Sri Lanka.

These species are often found in leaf litter, buttresses of trees, or on low vegetation within forests and home gardens. They prey upon geckos, mice, and lizards. The average length is 55cm.

The Hump-nosed Viper, is responsible for more bites resulting in hospital admissions than any other species in Sri Lanka. Hypnale sp. have a hemotoxic venom. The native name for the snake is 'Kuna katuwa', which means "rotten bone", probably due to the necrotizing properties of the bite.

No antivenom has ever been developed using the venom or a venom component collected from Hypnale sp. Bites are usually sustained on the hands and feet.