An evolved shark is meant to surpass their three successors that aren't evolved, but Behemoth wasn't there yet in the game. But still, despite not being true in game, Abyssaurus is technically as strong if not stronger than Behemoth (but weaker than Sharknarok).

If Kraken gets evolved i am sure that they will put him before Sharknarok even though he would be after Sharknarok normally.