All frogs in "Nyctimystes" have marks on their lower eyelids: lines, veins, or dots. Scientists think this helps the frog harder to see so it can hide from larger animals that want to eat it. Scientists tell "Nyctimystes" frogs apart from "Litoria" frogs because "Nyctimystes" frogs have vertical (up and down) pupils in their eyes and "Litoria" frogs have horizontal (side to side) pupils in their eyes.