A first for frogs. The mimic frog is the Congolese giant toad (Sclerophrys channingi). The snake is the Gaboon viper (Bitis gabonica):
“This is the first example in the world – that we are aware of – of a frog attempting to mimic a venomous snake,” says Eli Greenbaum at the University of Texas at El Paso. “It’s rare for frogs to be involved in a mimicry complex in general.” Michael Marshall, “Giant toad looks and acts like a venomous snake to scare off predators” at New Scientist
The toad also lets out a hiss when startled, like the viper’s threatening hiss.
A classic example of Darwinism at work, right?. It did a lot of good for the toad to happen to look one per cent like a venomous snake, so then it evolved to two percent and that did more good so it naturally selected to three percent and… Not really. Whatever happened isn’t a form of Darwinism.