Perhaps the most famous example is the early horse, Eohippus (also known as Hyracotherium ). About 50 million years ago, this small, forest-dwelling browser walked on four toes on its front feet and three toes on its hind feet. Each toe ended in a small hoof.
It sounds like you're referring to the concept of the — likely an analogy or a specific case in evolutionary biology, paleontology, or even a fable. three toes wrong turn