Agreed, T. Rex is much more famous than Archeopteryx. I'd hazard the guess that even old Brontosaurus (or whatever "he" is nowadays named) is ahead of the old bird.

I wonder if the author of your book wasn't an ornithologist in their second career; certainly a good case can be made that Archeopteryx should be the world's most famous, er, extinct organism. (But that wording ...!)