A stretchy and bendy bone setup.

This is a bone system for A:M 8.5. It consists of 18 bones and their constraints.
You will need to move the target bone to point the tongue in a certain direction. The tongue will automatically bend and stretch accordingly to this bone. You can also change the roll of this bone to bend the tip of the tongue.
You will have to do a bit of work to include this setup in your character (like creating a tongue bone and adding all my 18 bones to that). if you want a longer tongue have a look at the inverse bone and scale it right for your needs.
You may also want to adjust the bone original to change the direction of the tongues end/base.

All constraint setup is done in Pose1.
the setup is fairly easy to to, but shows some tricks and switches for beginner users.

Basically i'm stretching (aim at constraint with Scale To Reach) the main bone to the target (additionally i'm using a roll like target, to use the roll that you give the target).
I'm using filler bones (Bone1 to Bone4) to get a round bend. The setup for them is quite basic and is described below.

Inverter setup for thickness
The scaler bone scales like the main bone.
The inverter is a child of the scaler.
The inverse bone is stretched to the inverter and is positioned ilike this:

o==scaler=====> o==inverter==> <============inverse==o

This way the inverse will get smaller when the scaler gets bigger.

The bones Bone1 to Bone4 are arranged in a chain (attached to parent, Bone1 is parent of Bone2, etc.).
the constraints are
Bone1
translate to bone main bone to get the position of the filler bones right.
orient like bone original [Enforce = 100%]
orient like bone main bone [Enforce = 0%]
Bone2
orient like bone main bone [Enforce = 20%]
scale like main bone [Enforce = 30%]
Bone3
orient like bone main bone [Enforce = 50%]
scale like main bone [Enforce = 60%]
Bone4
orient like bone main bone [Enforce = 100%]
scale like main bone [Enforce = 100%]

The bones Bone1 through Bone4 each have a child called pos1 (to pos4). This is used to get access to the position of the filler bones. (I could also have just added a Bone5 for the tongues tip and then used each filler bone directly for the position, but this way the setup gets more clear)

Now we will need our final diameter scalers that will actually be used for mesh assignment:
You should not make these bones children of the filler bones or the pos - bones, because they woud inherit the size of these bones which we dont want. we want the size of the diameter to be in indirect proportion to the size of the corresponding filler bone.
So we create 4 independent bones called width1 through width4, which will be scaled like the inverter with Enforce=40/60/80/100, translate to the corresponding pos - bone and finally orienting like the corresponding pos - bone.

If not clear, please have a look in the project file to see how the bones are positioned and how their hierarchy is constructed.

Download tongue-contraints.prj