Gorn are cold-blooded, reptilian humanoids with a green rubbery skin and an average height of approximately two meters. Their ears are simple holes on the sides of their skulls, while their mouths boast an impressive array of sharp teeth and their hands and feet possess vicious claws.They are highly muscular and prefer warmer temperatures.
First contact between mankind and the Gorn took place in 2267, when they attacked the Cestus III colony, a world which was regarded as as part of their territory. At that time, they possessed a technology roughly similar to that of mankind.
Notes: Gorns bear strong ressemblances to Green Chaschs from Jack Vance's Planet of Adventure.
Source: Star Trek TOS “Arena”,