1948: When Stewart Springer, who worked for a Florida shark fishing company, reached inside the oviduct of a heavily pregnant sand shark, he was bitten on the hand. (Serves him right, you might say, for putting his hand there in the first place.) He had been nibbled by “an exceedingly active embryo which dashed about open mouthed inside the oviduct”. Springer had discovered one of the less endearing qualities of the sand shark – intrauterine cannibalism – in which the dominant embryo devours the other embryos until it is the only one left in the womb.
Source: Copeia, 1948