Everybody get on the floor

-Neural vertibrae: Either fatty hump like structure (akin to buffalo) for storage or a large 'sail' for thermoregulation (sunning for heat - unknown if spinosaurs are cold or warm bloods)
-Narrow skull shape: Suggesting similar build to crocodiles, snap shut technique for biting, very weak when opening jaws.
-Skull shape: Suggests poor torsion resistance, reinforces above point.
-Elongated body: Horizontal figure, more than likely to press off forelimbs to remain bipedal when stating to move or regain balance but occasionally quadrupedal.
-Amphibious: Likely aquatic and terrestrial
-Tail: Used for herding methods in water(?), too stiff for a whip like use, likely used as a rudder
-Likely larger than latter two.
-Teeth: conical for trapping and grip, not shredding or slicing.

-Tail: Large and heavy, not suitable for whip usage and will throw balance.
-Head: Large and heavy, thickened body due to support muscle, slowed or restrictive movement
-Bones: Hollow, structure potentially akin to birds to support muscle weight
-Skull: narrow snout and wide cranialallows for good binocular vision, many sockets for muscle anchoring and lightening of head
-Mandible: U-shaped for wider bite, lockjaw biting technique, likely to suddenly twist or turn head to create a more vicious tearing of flesh.
-Forelimbs: what the fuck is the point
-Teeth: Serrations, potentially infectious (retaining bacteria in serrations)
-Combat: Preferred hit mid-tall height, low can offset balance.

Tail: Used for balancing, modified structure in tail vertebrae and pelvis allowing for greater agility, large blade-like spines
Build: Incredibly bulky akin to T. Rex.
Skull: elongated, low positioning, nasal cavity suggests it relied heavily on scent
Teeth: Serrated
Bite style: Snap-lock, teeth set for slicing rather than tearing chunks

Spinosaurus would only be able to win if it were submerged and used similar hunting tactics to a crocodile, jumping out of the water to snap jaws around its prey's neck and rotating its body to tear open the neck and kill it. However, the jaw strength is not enough to withhold that form of movement and their neural spines will slow or even stop movement in water should they attempt a death roll.

Should the Spinosaur be on land instead of water, the Tyrannosaurus has its advantage of the bite strength, weight, and height range to attack the Spinosaurus with. The spinosaurus' build seems to primarily make it incredibly straightforward in movement on land and sea. Whereas the T. Rex is much more agile.

Giganotosaur is tall enough for the T Rex to attack, but chances are that the T Rex would be hitting along the upper areas of the body which is heavily guarded by bone or injuring the sides. The Giganotosaur's head is positioned lower where its entire posture tilts downwards towards the front, meaning it can use leverage and attack a T Rex's vitals by biting on the neck. T Rex's bite power is superior, but isn't as useful if it cannot get the Giganotosaur's neck or legs.

Spinosaur faces the same issue with Giganotosaur as it did with Rex. Giganotosaur will have a harder time trying to get the Spinosaur's neck, but will have the overall advantage with flexibility, agility and strength in comparison to the Spinosaur.

Gigantosaurus wins - Above reasons

T-Rex wins - Spinosaurus sucks

Gigantosaurus wins - Surroundings make no difference

Gigantosaurus wins - Not big surprise

Gigantosaurus wins - What do you know...

Spinosaurus wins - Heavier weight, less suited to wet/sticking conditions,
Spinosaur able to utilise advantages and attack with force.

Gigantosaurus wins - More agile due to modified skeletal structure along the neck, tail and pelvis

Spinosaurus wins - Due to T-Rex reasons

Gigantosaurus wins - Multiple foes too much for Spinosaurus to deal with,
will eventually tire and lose.