
Really. Just because it supposedly has that sail on its back doesn't mean it's agile enough to take down T-Rex.
For one, the fight was in a friggin' jungle. Doesn't the sail work more on intensely hot areas, such as deserts or something?
For two, I don't think Spino was designed for such fights. T-Rex is more fit for this, since it's designed to tackle ruthless herbivores such as Triceratops. Moreover, T-Rex had serrated, bone-crushing teeth, to take down actual dinosaurs its size (e.g. Edmontosaurus), while Spinosaurus had more pointy teeth, designed for gripping large fish.
Any ideas?