Recent material---Ibrahim and Sereno...has caused a storm of controversy, which is healthy. Spinosaurus did not have arms suited to quadrupedal walking. Since when? If the legs were strong enough to be a good fulcrum and well muscled enough...and the tail was thick enough, maybe the arms and hands seldom had to support full front body weight. Pangolins have been used as an example of what looks like an obligate quadruped walking bipedally a lot. Balance and body strength are the keys, IMO.
It is claimed Spinosaurus could not pronate its hands and therefore could not walk on its forearms. I call this into question. For argument's sake, I'll say it could not pronate its hands. Why would this be a barrier to quadrupedal walking?
It was proposed Spinosaurus faced its hands outward and walked like a walrus, a procedure that strikes me as unlikely.
What do YOU think?