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Genus of snakes

Echis (common names: saw scaled vipers, carpet vipers) is a genus of vipers found in the dry regions of Africa, the Middle East, India, Sri Lanka and Pakistan. They have a characteristic threat display, rubbing sections of their body together to produce a "sizzling" warning sound. The name Echis is the Latin transliteration of the Greek word for "viper" (ἔχις). Like all vipers, they are venomous. Their common name is "saw scaled vipers" and they include some of the species responsible for causing the most snakebite cases and deaths in the world. Twelve species are currently recognized.

Saw scaled vipers are relatively small snakes, the largest species (E. leucogaster, E. pyramidum) usually below long, and the smallest (E. hughesi, E. jogeri) being around
The head is relatively small and is short, wide, pear shaped and distinct from the neck. The snout is short and rounded, while the eyes are relatively large and the body is moderately slender and cylindrical. The dorsal scales are mostly keeled. However, the scales on the lower flanks stick out at a distinct 45° angle and have a central ridge, or keel, that is serrated (hence the common name). The tail is short and the subcaudals are single.

Species of this genus are found in Pakistan, India (in rocky regions of Maharashtra, Rajasthan, Uttar Pradesh, and Punjab) and Sri Lanka, parts of the Middle East, and Africa north of the equator. As they become more agitated, this stridulating behavior becomes faster and louder. This display is thought to have evolved as a means of limiting water loss, such as might occur when hissing. Venom toxicity varies among the different species, geographic locations, individual specimens, sexes, over the seasons, different milkings, and, of course, the method of injection (subcutaneous, intramuscular, or intravenous). Consequently, the values for Echis venoms differ significantly. In mice, the intravenous LD50 ranges from 2.3 mg/kg (U. S. Navy, 1991) to 24.1 mg/kg (Christensen, 1955) to 0.44–0.48 mg/kg (Cloudsley Thompson, 1988). In humans, the lethal dose is estimated to be up to 5 mg in some subspecies (Daniels, J. C. 2002). Venom from females was more than twice as toxic on average as venom from males. 6–48 mg (16 mg average) from Iranian specimens and 13–35 mg of dried venom from animals from various other localities. Yield varies seasonally, as well as between the sexes: the most venom is produced during the summer months and males produce more than females. and E. romani. A mitochondrial DNA phylogeny for the genus demonstrated the distinctiveness of E. borkini, E. jogeri and E. khosatzkii, but showed E. multisquamatus to be a synonym of E. carinatus.