With plant-eaters being huge, hunters have got a problem. How do you bring down something much bigger than you? It is a problem you can see in the savanna today. Lions tend to go after gazelles and other medium sized animals rather than elephants, which are simply too big for them. Even a buffalo can fend off a big cat. So you might think of apatosaurus as the dinosaur equivalent of an elephant, and triceratops as the equivalent of a buffalo.

What we have just said suggests that hunters would starve to death, which, of course, they don't. Some smaller animals, like wolves and dogs, work in packs to bring down larger animals, but in general, even big animals are much more likely to be eaten when they are eggs, small and growing up, or very old and just about to die. The easiest way for a hunter to get meat is from eggs and from dead carcasses.

So we can imagine that hunting dinosaurs were really meat-eating dinosaurs with a good sense of smell. If there was putrid food about (such as a dead carcase) they would be able to smell it.

Large meat-eating dinosaurs were probably very speedy when they were young, but slower and more lumbering when they got older. So young ones could have worked as a pack, bringing down young plant-eaters from a herd, or they could have waited in ambush, for example, near a waterhole.

So what is the point of a huge head and fearsome teeth? If you are to eat any meat, this is just the tools for the job. Eating a big plant-eating dinosaur would not be easy unless you had powerful jaws. The other advantage is that you could rear up and show your teeth. And this brings us to another point: hunters need territories that can be quite large. Why is that? Because they cannot expect to find eggs, young or old staying put in the same area just waiting to be picked off. Plant-eaters have to stay on the move to find more plants to eat, so hunters have to have big areas which are their territory to find enough food. This means that defending your territory is very important. Fearsome teeth are one weapon in keeping others away.