Serpent Folk?

[Yklikt]

In savage species some feats prerequisite say serpent or serpentfolk? What does it mean?

[Remuko]

Probably something explained in the Serpent Kingdoms or w/e its called book.

[Goaty14]

I don't know what it is talking about; but there is a possibility it could be talking about Yuan-Ti

EDIT: It does refer to Yuan-Ti as serpentfolk, however I was not able to find a feat the requires serpentfolk as a prerequisite.

[daremetoidareyo]

Serpent kingdoms either page 5 or 8 has a list of scaled ones and serpentfolk.