Aside from the initial paragraphs in the Feats chapter, which pretty much say that the DM is final arbiter on whether the players have access to any of these lost feats, there are no prereqs. I'd ask your DM first, and it might be good to have a backstory reason why your character would have access to forgotten lore such as this.
For instance, my new druid in a FR campaign will be starting out with this feat. I have it in her backstory that she spent much of her childhood being raised by dryads, which are effectively immortal as long as their oak tree doesn't die. My DM approved, even after looking at the Greenbound template, which definitely adds some hefty power to those summons. His rationale is that with an average combat round, the creature will take one full round to summon, then joins combat at the second round, at which time most equal CR encounters will probably be halfway done, and will only last for a few rounds afterward, so it wouldn't affect any future encounters. Thus, it's only really going to affect encounters with EL higher than the party, such as boss fights...
