While I was searching about some random stuffs I accidentally found an interesting article about dinosaurs and how they fight. I will share a portion of it and if you want to learn about more on how dinosaurs fight check out the site where I got this. (source: By Bob Strauss, About.com )

Offensive Dinosaur Weapons

It's a simple matter to distinguish between offensive and defensive dinosaur weapons: offensive weapons (like sharp teeth and long claws) were found almost exclusively on carnivorous dinosaurs, which preyed on gentler herbivores, while defensive weapons (like armor plating and tail clubs) were evolved by herbivores in order to fend off attacks by carnivores. A third type of weapon was employed mostly by plant-eaters: sexually selected adaptations (such as sharp horns or thickened skulls) wielded by males of the species to dominate the herd or compete for the attention of females.

Here's a rundown of the offensive weapons used by carnivorous dinosaurs:

Teeth. Carnivorous dinosaurs like T.Rex and Allosaurus didn't evolve big, sharp teeth merely to eat their prey; like modern cheetahs and great white sharks, they needed these choppers to deliver quick, powerful, and (if they were delivered in the right place) fatal bites. We'll never know for sure, but based on analogy with modern carnivores, it seems likely that these ancient predators aimed for their victims' necks and bellies, where a strong bite would cause the most damage.

Claws. Some carnivorous dinosaurs (like Baryonyx) were equipped with large, powerful claws on their front hands, which they presumably used to slash at prey, while others (like Deinonychus and its fellow raptors) had single, oversized, curved claws on their feet. It's unlikely that a dinosaur could have killed its prey with claws alone; these weapons were probably used to grapple with opponents and keep them in a "death grip."

Eyesight and smell. The most advanced predators of their day (like the man-sized Troodon) had large eyes and relatively advanced binocular vision, which made it easier for them to zero in on prey. Some carnivores also had an advanced sense of smell, which enabled them to scent prey from far off (though it's also possible that this adaptation was used to track down already-dead carcasses).

Momentum. Tyrannosaurs were built like battering rams, with enormous heads, thick bodies, and powerful legs. Short of delivering a fatal bite, an attacking Daspletosaurus could knock its victim silly, provided it had the element of surprise. Once the unlucky Stegosaurus was lying on its back, stunned, the tyrannosaur could move in for the quick kill.

Speed. This adaptation was shared equally by predator and prey, making it a good example of an evolutionary "arms race." Since they were smaller and more lightly built than tyrannosaurs, raptors must have been especially quick, which created an evolutionary incentive for the herbivores they hunted to learn to run faster as well. As a rule, carnivores were capable of short bursts of high speed, while herbivores could attain a slightly less brisk pace for longer periods of time.

Bad breath. This may sound like a joke, but paleontologists believe that the teeth of some tyrannosaurs were shaped so as to purposely accumulate shreds of dead tissue. As these shreds rotted, they bred dangerous bacteria, meaning any non-fatal bite would result in an infected, gangrenous wound. The unlucky herbivore would drop dead in a few days, at which point the same tyrannosaur (or others of its kind) feasted on its carcass.