To do this you'll need to extend SkeletonComponent so you can have 2 AnimationStates. Here's some code:

class YourSkeletonComponent extends SkeletonComponent {
	public Spine.AnimationState state1;
	public Spine.AnimationState state2;
	
public void Initialize () {
	super.Initialize();
	state1 = new Spine.AnimationState(skeletonDataAsset.GetAnimationStateData());
	state2 = new Spine.AnimationState(skeletonDataAsset.GetAnimationStateData());
}

public void UpdateAnimation () {
	skeleton.Update(Time.deltaTime * timeScale);
	state1.Update(Time.deltaTime * timeScale);
	state2.Update(Time.deltaTime * timeScale);
	state1.Apply(skeleton);
	state2.Apply(skeleton);
	skeleton.UpdateWorldTransform();
}
}
...
YourSkeletonComponent yourSkeletonComponent = ...
yourSkeletonComponent.state1.setAnimation("walk", true); // true means loop
yourSkeletonComponent.state2.setAnimation("rotateArm", false); // false means don't loop

Yeah, I had facerolled the keyboard to come up with that code sample. :p

SkeletonData stores the setup pose and data like skins, attachments, animations. Skeleton stores the state for an instance. Diagram here. AnimationState is a convenience class that makes it easy to mix (crossfade) and queue (for later playback) animations. You could do what AnimationState does yourself if you like, just by using Animation mix() and apply(). SkeletonComponent is really only needed to draw the skeleton. You can extend it to do your own skeleton manipulation, either by getting bones and changing their values or by applying animations however you like.

It just makes sense to extend SkeletonComponent and use AnimationState this way though. It's like giving the upper body its own animation state, and the legs its own animation state, or say, facial expression has its own animation state. Then you can manage and animate each of them kinda separately and cleanly.

Anyway, I just learned that the base (SkeletonComponent) class' methods need to be declared as virtual if you want to override them. http://msdn.microsoft.com/en-us/library ... 71%29.aspx

The virtual-override pair seems to be something of a self-documentation feature of languages (for when you expect a method to be overridden) that even the C++11 spec adopted.

I've refactored spine-unity a bit. There is now SkeletonComponent, which only draws the skeleton. Extend it to do your own thing. There is also SkeletonAnimation which extends SkeletonComponent and has an AnimationState. The AnimationState can either be controlled through the Inspector, or set the animation to <No Change> if you want to control the AnimationState via code.