Gorgonopsia (from the Greek Gorgon, a mythological beast, and óps 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago.
They are characterised by a long and narrow skull, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons.
Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite.
They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw.
The Gorgonopsids, nicknamed the Gorgons (as in Medusa), are a group of therapsids that are hard to miss. Their giant saber teeth are iconic and helped them secure the Permian all for themselves, ruling it until the very end. They were a ferocious bunch no doubt, but only one of them could be the most mighty and kingly, and it was, Inostrancevia. It hailed from Permian Russia, and is most likely the largest Gorgonopsid to ever live, but size was not the only trick it had up its sleeve.