Children's picture books, both fiction and non-fiction, play a vital role in introducing the reader to the natural world. Here we examine the representation of turtles, terrapins and tortoises (Testudines) in 204 English language picture books and find a mean of 3.9 (SD 9.1) basic biological errors per book. Only 83 (40.7%) of the examined books were found to be error-free in the representation of Testudines, with no significant improvement in biological accuracy being observed over time (book publication date range 1974-2017). Suggestions are made as to how biological accuracy of children's literature could be improved to help foster children's understanding and wonder of the natural world. Fantasy and imagination have an important role within children's literature, but here it is argued that the books children read should support future generations having sufficient understanding of the natural world to imagine the solutions to current environmental problems. A role of children's picture books should not be to reinforce biological illiteracy.