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I know there's bipedal for animals that have 2 legs, but what of animals with 2 arms?

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@whoabackoff yeah, that's what I meant. –  OghmaOsiris Jul 18 '11 at 18:11
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Would this be a word that could apply to say, a Centaur, which is a quadruped, but also has 2 arms? –  aslum Jul 18 '11 at 18:19
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@whoabackoff : This is the best name ever for replying to comments with a disagreeing comment. :-) –  T.E.D. Jul 18 '11 at 18:48
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Bipedal means two feet. Just sayin' –  Matt Эллен Jul 18 '11 at 20:43
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@T.E.D.: "Dragon" is such an overloaded terms, there are Dragons of all kinds of shapes with zero, two or more arms "out there". –  Joachim Sauer Jul 19 '11 at 12:58

4 Answers 4

up vote 10 down vote accepted

Well, logically using the Latin roots, the word would be either bibrachial or bimanual. Brachium is Latin for "arm", and manus is Latin for hand. In my book the distinguishing feature of an arm is that it has a hand (manipulation mechanism) at the end of it, so they are basically the same. But whatever works best for you.

Bimanual does seem to exist in some dictionaries. However, the definition seems to be more like "something that requires (a human being) to use both hands to operate".

I think in certain very specific circumstances (e.g. a biology paper) it would be acceptable to use it anyway, as long as you define it for your readers up-front. If that will make things clearer and more succinct in the long run, it'll be worth it.

Just be really careful about not using that word in realms where it already has another meaning (which from my searching seems to be mostly power-tool operation and certain medical realms).

Alternatively, you could use something like bibrachial. It seems to be a much more obscure word. This makes sense, as lot of folks can work out that "manual" is related to hands because it actually has that as an English meaning, but brachial isn't really used in English to talk about arms much. It also appears to have an existing medical meaning which I'm guessing (I am not a doctor) amounts to "in both (human) arms". So the same caveats apply.

But since manual is Latin for "hands", brachial is probably better if it is really arms you are after.

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The definitions I find for bimanual means: with two hands. –  OghmaOsiris Jul 18 '11 at 18:10
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I think bimanual is a non-starter here, and even horses have a brachial plexus‌​, so that's out too for me. –  FumbleFingers Jul 19 '11 at 3:26
    
I actually began the search because of a sci fi book I was reading. so thinking outside the box and not being terra centric I like the Idea of brachial. there are quadrupeds here on Terra. someday we may just run into some quadrabrachials, multibrachials or polybrachials as we use polydactyly –  user59226 Dec 9 '13 at 2:37

I'll ignore things like octopuses and starfish.

Tetrapoda is the taxonomic group of four-limbed animals. Not a particularly useful term after the Permian extinction, since after that pretty much all animals with limbs had four. It's just a matter of whether you call them all "legs", or call two of them "arms".

As @Saeed Neamati says, the main reason we don't have a word for "two-armed" is because there ain't no such animal. Apart from primates, who are to an extent defined as such (though I'm not completely comfortable calling a loris's forelimbs "arms").

You might call a squirrel's forelegs "arms", but that's a bit metaphoric/anthropomorphic to me.

TL;DR: Animals with two arms are called Primates.

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I have to admit the only example outside of primates and fantasy creatures I can think of is the bipedal dinosaurs. Raptors, T-Rex, etc. –  T.E.D. Jul 19 '11 at 12:06
    
@T.E.D.: I honestly don't see how bimanual can be stretched from operation requiring both hands to animal with two arms, but apparently you and at least 8 others are happy with that (as a neologism?). Lack of support notwithstanding, I'm leaving my answer in. –  FumbleFingers Jul 19 '11 at 15:05
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It wasn't from any existing meaning, but from the Latin. This is very common for technical jargon. In technical papers there is really nothing wrong with creating a new jargon word for a relatively novel concept, as long as it makes the discussion easier and you take care to define it the first time you use it. bipedal certainly started out the same way in somebody's Anthropology paper. –  T.E.D. Jul 19 '11 at 15:33
    
@T.E.D.: If we were having this discussion because we were discussing new technical/academic ideas where we needed a coinage to cover a new new context, I'd probably go for bimanual, bibrachial, or something. But we're not and we don't. OP asks if there's a word, and to my mind there just isn't. Of the words we do have, I still think primate is most appropriate. –  FumbleFingers Jul 19 '11 at 20:13

In vertebrates, if the front appendages are not used primarily for walking, they will be called 'arms' instead of the usual legs (e.g. kangaroos, primates). Mammals have at most 4 appendages so there's no real room for more than two arms (please ignore clever rodents and flying squirrels).

In insects, spiders, and other animals with more than four appendages, they are all just called legs even if they use them mainly for not traveling.

So there really is no word for it, and the lexical gap remains only in science fiction.

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...but I'd go with the neologism of 'bibrachial' mentioned elsewhere here if biologists found a need. –  Mitch Jul 19 '11 at 12:42
    
You forgot birds and bats and manatees, amongst others. –  tchrist Dec 9 '13 at 3:36

Bipedal doesn't mean animals with 2 legs. It refers to animals who use their legs (rear limbs) to walk. These are really different. We also have quadrupeds that refers to animals who walk on 4 legs. Cow is a quadruped, and kangaroo is a biped.

But now let's enter into physiology. Do you know a kind of animal which walks on it's hands? Because there is no such an animal, there is no name for that.

No external object, no thought of it, no name for it. :)

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Well, actually there are. Most Great Apes walk on their feet and hands on the ground (knuckle-walking), and hands only in the trees (brachiating). –  T.E.D. Jul 18 '11 at 18:18
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Great Apes do walk on feet and hands. But brachiating means swinging from tree branch to tree branch using only arms, which many great apes also do. –  Peter Shor Jul 18 '11 at 18:20
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@Peter Shor - Yeah, figured that out in time to correct the comment (and annoyed at my Anthro 101 prof for steering me wrong). –  T.E.D. Jul 18 '11 at 18:21

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