Our BioMystery image this month is a large part of a much larger creature, but what part? What is the purpose of this structure, and how might its development be explained? While the original owner of this body part is no longer with us, curiously the cause of this extinction may have been a kind of evolutionary suicide. For now, we won't reveal where this picture was taken because that might be too big a clue. The answer can be found in the back of this issue on page 194.