Caenophidian
Caenophidia is the technical term for "advanced snakes", an evolutionary group that contains vipers, elapids, sea snakes, and colubrids. Venom is unique to caenophidian snakes, and no caenophidian snake has retained vestiges of the pelvic girdle, which is present in other snakes. Additionally, the broad belly scales and rows of dorsal scales correspond to the vertebrae in Caenophidians, while they do not in Henophidians or Scolecophidians.
Caenophidia contains most of the diversity of extant snakes, with over 3,000 species. They are believed to be a recent radiation, having evolved in the mid-Cenozoic.
