Their basic outer structure was that of a humanoid except that their faces resembled those of dogs.
In the 1970s, four space greyhounds, piloting metallic, spider-like vehicles, were chasing after the Third Doctor, Jo and the Brigadier in Bessie. The Brigader killed one with a bazooka while Jo, using the small mirror in her make-up bag to reflect a shot fired at one of the remaining three, killed another. The Doctor, using his sonic screwdriver and a loudspeaker, overloaded the remaining space greyhounds' brains and put them to sleep. (COMIC: The Forgotten)