Sybil's parents. There's some fun size difference between them.
Cecil is a vinesnake (and Sybil gets her pointy nose from him, and her natural height).
Beatrix is a black mamba (black momba haha).
Funnily enough, I didn't originally give Beatrix a hood but, eventually decided on it because Sybil has a hood. Black mambas aren't actually supposed to have hoods which has resulted in me making this overly complex family tree to explain Sybil's genetic features.