VIRGIN SHARK BIRTH FOLLOW-UP: Robert Crawford writes me with a third explanation for the King Of The Jaws: one of the sharks switched gender. Or sex --I can never remember the difference. Anyway, here's Robert:

Something to think about in the shark story. While sharks aren't closely related to them, clownfish -- the ones that live in anemones -- change sex naturally. The largest in a community is female, the second largest male, and the others are immature or indeterminant. If the largest dies, the second largest takes it place -- switching from male to female -- and another takes the place of the male.

He brings links to this clownfish page and this discussion about another cross-gendered fish.