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Which Came First, the Chicken or the Shark?

Shark egg cases, sometimes called “Mermaids’ purses,” can wash up on beaches, dried and stiff. Researchers found this one at the bottom of the Southern Ocean off Antarctica. In May 2006, WHOI biologist Rudi Scheltema co-led an expedition to study whether swimming larvae of ocean-bottom animals are transported across turbulent currents separating Antarctica from South America. Dredges brought up bottom-dwelling worms, starfish, crabs, snails – and this egg case of a bottom-living shark. Inside, almost like a chicken egg, is a yolk sac and a developing (pink) embryo. (Photo by Ellen Bailey, Woods Hole Oceanographic Institution)