Fantastic Beasts and Where to Find Them is a pseudo in-universe book describing magical animals from the Harry Potter world.
Is it an exhaustive list though? Do other creatures exist that don't feature in the book?
I'm asking because of this comment, by Gabe Willard:
No creatures matching her description are listed in Fantastic Beasts and Where to Find Them. If you can, make an answer. I'm fairly confident she's a Muggle snake, however. Such an absence from FBWFT would be unexpected.
Is such an absence unexpected? Are other 'well known' creatures that aren't featured in that book?