Animal of the Week August 15, 2005 -- A very very big shark indeed, but extinct, phew

Last Monday evening, I was watching CSI Miami when there was a peculiar percussive sound. I looked up and saw on the ceiling a large round beetle, on closer inspection it turned out to be a harlequin (animal of the week March 21, 2005)!!! First thing on Tuesday morning, I logged my sighting with the harlequin survey (http://www.harlequin-survey.org/).

This week's animal is a little bigger, welcome Carcharodon megalodon (megalodon). At something approaching 15 m long and 20 tons we should be pretty glad that this close relative of the great white doesn't still exist. Until about 1·5 million years ago, warms oceans were home to the largest meat eating sharks that ever lived. Because sharks have cartilagenous skeletons, the fossil record of megalodon is rather poor, but their teeth survive in abundance. Although there's not much evidence to go on, the size of the teeth and their similarity to those of great whites suggests that megalodon was a scaled up Jaws. Likely preying on whales—the babies of which they could have swallowed whole—it is difficult to imagine what caused the extinction of this super predator. The loss of warm tropical seas due to continental drift may have played a part. But maybe the evolution of warm-blooded, highly smart killer whales turned the tables on the fishy leviathan. Although some people reckon there may still be a few megalodon left in the depths, this seems unlikely. But these people might be pleased to know that the director of Speed, Jan de Bont, is working on a film, Meg, due out some time next year about such a conceit, the rest of us will probably remain indifferent (if I thought there were going to be more cows in tornados as seen in de Bont's Twister, well, I might be more enthusiastic).