Minor spoiler! Which is bigger the gargantuan fossil in Subnautica's lost river or...

[jcewazhere]

the new beast frozen in ice in Below Zero?
If I remember right you could easily fit a seamoth in the skull of the creature in the lost river.
This meat popsicle seems to be possibly bigger than the emperor or dragon but not the biggest creature we could have.

[HeyThere]

No, the gargantuan fossil is MUCH bigger than the frozen leviathan. Sure, the gargantuan fossil is... Just a skeleton, but if that thing also had meat on it's bones still, you would totally see how truly big it really was.

[Biderbeck]

mega fossil is bigger. the part you see is only the head and is 1/3 of the entire fossil. the frozen beast can fit inside the mouth of the part of the mega fossil you can see in subnautica.

[Cougarific]

Yeah the head itself is almost as big as the entire Frozen Levi.