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| | Bites Venom |
 | | The venom duct is surrounded by small masses of glandular tissue, the accessory glands, which may act as valves to regulate the flow of venom to the fang. |
 | | Africa’s rich venomous snake fauna is dominated by true vipers (ncluding arboreal vipers, desert vipers, nightadders, puffadders, and saw-scaled vipers), terrestrial elapids, (cobras and mambas), molevipers (Atractaspidinae), and two of the world’s four deadliest colubrids, the boomslang (Dispholidus typus) and the African birdsnake (Thelotornis kirtlandii). |
 | | It is probable that venoms and venom mechanisms evolved several times among snakes, increasing the diversity of venom chemistry and of the venom apparatus. |
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