Originally Posted by
MiniPrinny
Hyenas are the immediate example. But also blue and killer whales, hamsters, elephants, mole rats, meerkats, and depending on how you look at it, lions. Lions are an interesting case because the females appear smaller, but male lions are often less strong, have less endurance, and are more suited for mating and defending the home than hunting and providing for the pride.
Edit: I forgot about bonobos. They're closer to us humans in dimorphism, but they have purely matriarchal societies.