Spinosaurus

Eh, I don't think T_Rex would ever win.

I think Rex would win in a fair fight. The jaws on that thing were unbelievable.

You can't say never. What if the Spinosaurus/Tyrannosaurus stumbles over a rock or a tree trunk and down a cliff or ontop of another random object which then impales it?

I don't understand why people on this thread think the idea of Spino winning is stupid. The fight could have gone either way. Sure Tyrannosaurus had an imppresive bite force, but it's not like Spino has a weak jaw. Not to mention unlike T.Rex's arms, Spino's was no joke. 7 feet long with 3 foot claws at each end. It was larger as well, and far more agile which compensated for it's lighter skeletal structure. There's a theory among Paleontologists that Spinosaurs typically hunted by hooking onto its preys neck and then using its arms to break it (which is what we saw in JP3). Like I said earlier, the fight can go either way. In JP3's case, it shoulda went to the T.Rex. It may be smaller, but it's built like a tank for crying out. At the end of the day, it's the first bite that counts, as well as other factors like the environment for instance.

Most people here don't think that it's stupid, just that it would be uncommon. Now as for your points, I have to say that some of them are flawed.

1. Spinosaurus did indeed have a "weak" jaw. It was very strong, but compared to something like a Tyrannosaurus it was puny and it probably wouldn't be strong enough to cause nearly enough damage to kill a T.rex.

2. Since we haven't found it's arms yet we can't know how long they were., but they were probably around that size.

3. How can something be larger and more agile? I personally think that Spinosaurus was a bit lighter than Tyrannosaurus. Higher and longer, but not as robust and therefore not as heavy which means not as powerful. The Rex would probably have the advantage when it comes to agility, because it was shorter and (imo) heavier, it would've been able to turn faster and it had massive legs. Spinosaurus on the other hand was very long and had a gigantic sail which would hinder him even more than his unusual length.

4. Spinosaurus probably didn't hunt like that. It would use it's long snout to grab a fish and bring it on land, then it would use it's arms to gut it. When faced with terrestrial prey it would probably hold onto it with it's jaws (and the long teeth which were perfect for gripping) and then just claw the living hell out of it. It wouldn't be able to snap it's neck, like shown in JP, because it couldn't move it's wrist like that (for that matter, nothing except for humans and some primates can do that).

According to some people, that damn sail made it faster and more agile because it would have been more aerodynamic. I see that sail as nothing more than for mating purposes, thermal regulation, and intimidation. In a fight, I think that sail would so nothing but screw the Spinosaurus over,

The sail would actually be very helpful (imo), because it would make it look   a lot larger. If I was a Carhcarodontosaurus and would see a Spinosaurus which looks like it's almost double my size (because of the sail) I would just run away and Thermoregulation in such a scale can be a life saver. It doesn't matter if you're in a desert of a rain forest, if you stay in a river almost the entire day, Hypothermia will be a huge problem.

I know, but I was referring to once it was actually in a fight, not its everyday life. Of course the sail would be helpful on a day to day basis, why would it have it if it wasn't used for anything?

I see. I miss crucial things like that from time to time.

Same here. Part of being human I guess.