UFC Light Heavyweight Champion Jon Jones has an amazing ability to apply little used techniques in the Octagon, and against Glover Teixeira, Jones was again able to bring out a little used shoulder lock.
First let's start off with the actual attack by Jones, you can click to get a gif right here.
The technique itself is actually a very, very old and universal shoulder attack. It is taught in Japanese Jiu Jitsu styles and also found the European combat manual the Flos Duellatorum, used as part of dagger fighting and wrestling, and it is taught in modern grappling classes both standing and on the ground.
The technique is fairly simple, Teixeira has an under hook and Jones brings arm over and around to get a very tight overhook. Jones slides his grip down to Teixeira's elbow and brings it up and in, torquing on the shoulder. It clearly impacted Teixeira as he requested ice on the shoulder, and the targeting of the right arm was likely a deliberate effort to reduce the power of Teixeira's right hand.
Here is Stephan Kesting showing the shoulder lock and a counter he learned from Erik Paulson.
A Trick from the Underhook (via Stephan Kesting)
This shoulder lock can be applied on the ground in a variety positions. Frank Mir famously used it from the guard against Pete Williams, but it can also be applied from the top as well. To close, here is a look at the Over Hook Shoulder lock from the guard being taught by some of the late and great Billy Robinson's students.
No Gi BJJ Techniques: The Overhook Shoulder Lock (via TakingItToTheMMAT)