No. Think bigger.
They also could've adapted the Dodgson storyline unused in JP2 to fill in said run time. Would've been interesting. Anyway, Spinosaurus Eugyptigis was indeed a real dinosaur (whose only fossil was bombed out of existence in the battle of Britain in WWII) that was a hunter, while T-Rex was a scavenger (hence the useless tiny arms), and therefore, it's more plausible for Spiny to attack Rex. And sure, they're not from the same time, but In-Gen made them all at once, plus it makes the movie even more adventurous to pit dinos against each other that have never met up in history before. And supplies great visuals of dinos together.
Also, the original had dinos from mostly the Triassic period, and none of the cool ones from the Jurassic period, but the name sounded better.
Good adventurous flick though. A fun ride for JP fans, but not so much if you're used to reading the books and viewing the films with all the techy stuff.