Instead, getting large and brawny was the favourable adaptation. The herbivore Ectoconus (a member of the Periptychidae, which may be related to living hoofed mammals, the ungulates) reached about 100kg (220lb) within a few hundred thousand years of the extinction. In geological time, that"s the blink of an eye. "It"s mad really that they"re getting that big that quickly and specialising that quickly," says Shelley. "And you see, once you get larger herbivores there are larger carnivores, and they start popping up pretty quickly."