It would be neat if, say, dashed lines were used for all the descendants of LISP that are Lisps.
I mean, from the ones shown, it's sort of obvious, but I'm thinking in general. Also, Common Lisp, Racket, and Clojure are different enough that they count as separate languages in their own right, rather than 'variations', which a dotted line might imply.
How about: If you program in it using s-expressions, it’s a Lisp.
I'm not sure there is such a thing as a "Lisp." If you mean S-expression language, just say s-expression language. Wedging in Lisp as a substitute conflates the issue.
Now, you might argue that means Logo is not a Lisp, but it is actually extremely similar to basic Scheme. You could turn an interpreter for one into an interpreter for the other with mostly minor tweaks. It's also a dialect of Lisp historically.