sentences:  Similar-sized predators in modern predator guilds are separated into different ecological niches by anatomical, behavioral or geographical differences that limit competition.Niche differentiation between the Dinosaur Park tyrannosaurids is not well understood.In 1970, Dale Russell hypothesized the more common "Gorgosaurus" actively hunted fleet-footed hadrosaurs, while the rarer and more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) were left to the more heavy built "Daspletosaurus".