Large scaled pit viper

One of the beautiful pit viper species found in the western ghats. There is only one morph of this species found so far and it sharply resembles the pit viper species(pope's pit viper) found in the north east India. One more interesting fact of this species of viper is they are oviparous i.e., they lay eggs. Then the question comes why are they grouped under family "Viperidae"?