Pharyngula

Shark with legs?

Posted by PZ Myers on July 29, 2007
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A little knowledge would short circuit a lot of strange speculation. That picture to the right is of a shark caught in Malaysia, and people are calling those odd dangly bits “legs”. Despite the fact that someone said what they actually are in a comment early on, there are people arguing both that a shark with legs is evidence for evolution, and that it is evidence for creation.

They’re both wrong.

It’s a male shark. Those are the shark’s claspers, or intromittent organs. The shark does the usual act you’d expect with a female of the species, and like many shark species, it has clasper spurs, or little poky bits that help lock the organ into the female’s cloaca while he gets happy.

They aren’t homologous to legs at all. We also wouldn’t expect to find legs on a shark — they aren’t in the lineage that led to tetrapods.

I’m actually most surprised that a worker at the Malaysian Fisheries Development Board, who found this animal, didn’t recognize that these were just ordinary claspers. Anyone who has worked with sharks for even a little while would know about these structures. I suspect someone at the board is pulling the media’s, and the public’s, leg.

You know you want to see this: here’s a photo of two sharks getting affectionate. Shark lovin’ often involves a fair amount of biting and tearing, and leaves scars that you can find in captured specimens, so I don’t recommend trying this at home. Especially since sharks don’t believe in safewords.

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Comments

  1. #1 Matt
    May 17, 2009

    “yeah but the first feet probably were not “feet” either. the process of evolution involves mutations, and this is an example of a mutation could have lead to feet. it would be unintelligent to assume that the first feet were actually intended to be used in the way land animals use them. It would be even more unintelligent to think that something hand designed everything on earth..”

    so legs really used to be sex organs? all this time, i had no idea that i was using my penis to walk.
    dude, seriously. feet evolved on fish that lived either at the bottom of the ocean or in shallow water first. in either of those, feet would help it move around. eventually they started finding land and walking up on to it. the fish that couldn’t survive very long on land died off and the ones that could lived. this is called natural selection. only the strong survive. of the fish that survived, some of them probably were able to breath air somewhat, but of course they wouldn’t be able to get enough to survive. the ones that could get enough air to last the longest on land would live, the others would die off. eventually, gills would develop into lungs after several million years of species dying off and being replaced by new and better species. the mud skipper has both gills and lungs and is believed to be a transitional species. if you’re gonna start telling people how things work, make sure you know what you’re walking about.