We've all got our hot-button mini-issues when it comes to books. You know the ones, where it doesn't have a lot of effect on the text as a whole, but oh, your teeth, they are gritting. (Mine is that good ol' Mean Librarian stereotype. Thanks, author. We've got enough trouble getting the little blighters in here to check out your book in the first place, now you're going to undo all that work?)
Anyway, this person's is authors or illustrators who didn't do their natural history homework. Swing on by Strollerderby and check out this piece called 5 Nature Facts Kids' Authors Should Tattoo on Their Forearms.
Apropos of that, what's the most meaningless detail in a book (can be picture or text) that still made you shriek aloud in impotent rage? Mine was the presence of teddy bears in a book that took place in 1895. (Check out the Wikipedia entry if you don't know why I gnawed my knuckles in annoyance.)