The sport pankration in the ancient Greek Olympics is similar to today's mixed martial arts in that it restricted only a few particularly damaging attacks so that competitors will use a mix of stand-up, wrestling, and groundfighting. But something I've noticed in many depictions of pankration is the use of single arm locks (attacking shoulder or elbow) after taking someone's back. It just seems unusual to me because in MMA, back takes usually end up in rear naked chokes, which seems like a much more stable option.
Was this actually a common offense in pankration, or was it just artistic cherrypicking? If it was common, why do we see it in ancient pankration but not modern MMA (e.g. ruleset)?
Pancrastinae, a Roman sculpure based on a lost Greek original. It depicts a fighter taking the back of an opponent on 1 hand and knees and using his left hand to hyperextend his opponent's right arm. It's hard to see from this angle, but his left leg is hooked around his opponents' to prevent him from easily turning and relieving the pressure on his shoulder.