It is definitely a Senecio (Ragwort), or at least was once a member of
that genus. Senecio was a large "dustbin" genus, and a number of
smaller genera have been removed from it in recent years. Yours likely
is now to be found in Packera.

Can you tell us whether your plant appears to be annual or perennial?
Does it have tap or fibrous roots? It is hairy or bald? At first
impression, it looks like the former Senecio glabellus, now Packera
glabella. If your plant has fibrous roots, it's a good candidate.

As to why it's not in your wildflower book, remember that for every
plant which gets its photo in a book, there may be a dozen similar
plants which are not featured.

Monique Reed
Texas A&M