Spinosaurus aegyptiacus : bipedal or quadrupedal ?

Bipedal, but still pretty short

Also, T.rex, Carcharodontosaurus, and Giganotosaurus are larger

Well , based on facts there are more chances that it was bipedal so I agree ;) but spino was the largest by length and height, tyrannosaurus , carcharodontosaurus and giganotosaurus are larger in weight

In my opinion it walked like this-

^Concur.

Yeah that could be an accurate way I agree

I personally don't know if it was Bipedal or not.

But I do have one question, why are both of my skeletons drastically different? They have to be different species of Spinosaur or something like that. 

^The original assumption of S.aegyptiacus was that it had a full, semi-circular sail and it walked on two legs. New fossils show that the sail dipped down in the middle and its legs were shorter.

Looking at both fossil photographs in the OP it looks to me that the second, smaller fossil may be that of a juvenile, especially when you look at the difference in grandeur of the sail and the skull. IMO, this may suggest that young Spino's are primarily quadrupeds but as they mature they shift to a more upright posture becoming both quadrupedal and bipedal as adults, much like many Parasaurs.

You guys do know that more than 60% of the first photos skeleton was speculative, right? We didn't have much to go on then, but now we have a more complete skeleton so spino IS quadrupedal. Thats coming from someone who's fav movie is Jurassic Park III.

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Sips even if this topic is a bit old, I perfectly know that many spinosaurus skeletons are speculated cuz it is really rare to find a complete skeleton instead of some bone fragments, I'd still say it was bipedal but short and close to quadrupedal design

I meme everything are you still active on here? Do you remember me ? I died 2 years ago but now I am BACK!

Tripedal XD. I think it was bipedal with short legs, and with it's posture somewhat more vertical than typical Theropods, basically giving it a little bit of a tripod position, which would give it a center of mass close to its hips, so it doesn't topple over. Definitely nowhere near the reconstructions of old vertical though. 

It is known that it was quadrupedal opinions don't matter it's fact that it's quadrupedal Bipedal just doesn't work for its lifestyle. We know it ate mostly fish and smaller dinosaurs. If it were bipedal it would fall over every time it hunted, I donno about you but to me that seems like a major set back.

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Sea birds and other marine feeding birds are bipedal, so Spino could be the same. If it had a posture like I mentioned it wouldn't necessarily fall over all the time, and if it swam or dived to catch fish, that wouldn't be a factor.

Spinosaurus was just a giant crocodile with a spine on its back. Tripedal positions aren't possible with Dinosaur hips. I hope you're memeing when you suggest tripedal positions because it's absolutely ridiculous.

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Unfortunately we have too less skeletons and bones to be sure if Spinosaurs was bipedal or quadrupedal.

We can just try to deduce it by some characteristics of its bones, such as the toes which are plat on the lower part which touches the ground, just like ducks or acquatic birds. This probably makes Spinosaurus not like a deadly theropod like Charcarodontosaurus or Tyrannosaurus but more like a fish eater...a giant crocodile as you said.

To me it can be both, sometimes it walks on 4 legs and sometimes it walks bipedal.

I didn't mean quite like the old drawings, I was kinda exaggerating, just somewhat inclined, or more like this:

Here's some reasoning for it, and a link to more in depth explanation I can't provide: https://thepaintpaddock.wordpress.com/2016/07/16/t-rex-vs-spinosaurus-the-truth/

https://www.youtube.com/watch?v=6oCqSqY7FiI

I got what you mean TheLazyFish, I also think that spinosaurs could look like that, probably less feathers, but the design could be that

It looks a bit suited for cold climates to me, I think it would have coloring more suited to a swamp environment, to camouflage a bit. Other than that and the slightly excessive feathering, I think it looks pretty realistic.

I think Spinosaurus switched back and forth between Bipedal and Quadrupedal stances. I don't think spinosaurus would have feathers due to its semi-aquatic nature I believe spinosaurids would gradually evolve away feathers. Also looking at the spinosaurids family tree, they evolved from megalosaurians which diverged before more bird-like theropods evolved (I.e. Carnosaurians "Allosaurids and Carchardontosaurids" and Ceolosurians "Tyrannosauroids, Orthinomimids, Dromaeosaurids, Troodonids, and Birds)

Well, ducks, swans, geese, etc. Have feathers, so not exactly out of the question. Best example I think would be penguins. My opinion though. I kinda agree with your opinion on switching stances, but I'm not sure exactly how it could walk on four legs, definitely not on knuckles though XD.