Are there any animals with 3 legs, five legs, or odd number of legs with the exception of sports?

Question

And why is there not? Or, if there are why the odd number?

Answer 1

Let me say you had a 5 legged creature. Lets see the pro's and cons.

Having 5 legs over 4 legs
5 legs geared for speed is ineffient because at one point you will be on 2 legs, which requires a balence on 2 legs brain mass. So you have the same amount of brain mass, and traction can be increased with bigger feet. Now also notice three legs are less ergonomic then two, since weight must be distributed equally to keep brain mass down. Basically, having 5 legs is slower then 2, and gains nothing.

Having 5 legs over 6 legs.
If you want 5 legs over 6 to keep control but gain speed, that won't work either. 5 legs takes up far more brain mass then 6 legs to control. And the entire point of having many legs is to make it easier to balence, and thus reduce it.

So you see, having 5 legs really isn't a good idea for any species. You either gain mass, or lose ergonomics. Having a fifth muscular limb just isn't smart.

There are exceptions. First and foremost is things that don't walk. Such examples are starfishes, snakes, and snails. These are best suited to no muscles, or one muscle. Second are tails and antennas. While having a fifth limb is stupid, having something that purely helps you balance or detect is not. It can be lighter or more ergonomic to have a seperate body part for them.

To the question of 3 legged animals and such -
There aren't any odd legged animals, but there are odd extremities on some animals animal. Such as a snail, starfish, or snake.

Answer 2

Star fish, and their kin have radial symmetry. They can have odd numbers of legs.

Everything that is nearer the earthworm, including insects and people, have a different symmetry, where one side mirrors the other. (I've forgot the name of this, bilateral maybe.)

One small note, although we are symmetrical on the outside, on the inside, things are not arranged that way.

Answer 3

Starfish have 5 arms.

Answer 4

There was "Blinky" the three-eyed fish in an episode of The Simpsons several years ago.

Answer 5

star fish have 5 arms

Answer 6

A snail has one foot.

Answer 7

yes my dog Tripod