User blog comment:JakeTehCrabsquis/Theories./@comment-75.37.198.173-20170304061948/@comment-30868164-20170306144100

You mean the super huge skeleton that people want to call the Titan Leviathan? That thing died before the Precursors got there. And the other large skeleton that is just a head, that died about 7000 years before the player even got to the planet (so before the Precursors got there, the left the planet a mere 1000 years ago).