Bitten

There's a film out at the moment called Mega Shark vs Giant Octopus. Now, while I'm sure that almost everyone has a soft spot for giant-sized sea beasties - and especially sharks and octopuses - this film will probably not be an oscar winner. Harsh to judge a film on its title alone, but... You know.

I don't know too much about fossil octopuses, but the Giant Octopus that's currently kicking about is the Enteroctopus. A good name, worthy of a film itself. They only get up to about 20-23 feeet long, though. Not really that giant.

Mega sharks, however, are another matter. The undisputed mega shark was the Carcharocles megalodon. It was a relative of the great white - Carcharodon carcharias - and in fact was until quite recently assigned to the same genus. Megalodon, as it's usually called, means big tooth. Do I need to tell you why? Okay. It had very big teeth. No - bigger than you're thinking. No - hold on - not that big. Be realistic. The biggest complete tooth ever found was a little over 7" long.

The estimated maximum length of megs has been the subject of some debate. The best approach is the use the closest living relative, the great white, as a comparative measure. The technique is to scale up from tooth size and although different figures have been bandied about over the years, current thinking puts the approximate maximum length at around 60'. That's similar to a good-sized sperm whale. There have been bigger sharks, but not carnivorous ones.

Great whites attack a potential meal by ripping out a big fleshy lump - ideally the stomach area - and then coming back in for the kill once the thrashing around has abated a little. Megs would consider seals a bit of a light snack and there's evidence they used to attack whales - vertebrae with tooth scars etc.

Like many sharks, megs would have grown teeth constantly, shedding as they became worn, broken or loose during lunch. It's thought they would have had around 250 teeth in their mouth, too, so for every one shark there would have been a great many teeth throughout its life.

Megs died out only about 1.5 million years ago, and while many people would like to think there are a few still about, lurking in the depths, many others are very glad they are gone. Snorkelers and surfers especially.