After Uetz, Etzold & Chenna, 1995-2014 [“The Reptile Database”]

<==o Viperidea Oppel, 1811 (vipers, rattlesnakes, and relatives; kyykäärmeet)
   |--o Azemiops Boulenger, 1888 [Azemiopinae Liem, Marx & Rabb, 1971]
   |  |-- A. feae Boulenger, 1888
   |  `-- A. kharini Orlov, Ryabov & Nguyen, 2013
   `--+--o Causus [Causinae Cope, 1859] (night vipers; konnakyyt)
      |  |-- C. bilineatus Boulenger, 1905
      |  |-- C. defilippii (Jan, 1862)
      |  |-- C. lichtensteinii (Jan, 1859)
      |  |-- C. maculatus (Hallowell, 1842)
      |  |-- C. resimus (Peters, 1862) (viherkyy)
      |  `-- C. rhombeatus (Lichtenstein, 1823) (nuolikyy)
      `--+-- Viperinae Oppel, 1811 (vipers; kyykäärmeet)
         `-- Crotalinae Oppel, 1811 (rattlesnakes; kalkkarokäärmeet, kuoppakyyt)

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