Depicted here and often seen in heraldry, it's a two-legged winged dragon with a barbed tail
The wyvern has only two legs, the body curling away into the tail,... [DOC] [TLE] Dictionary of Heraldic Beasts at Mostly Medieval - Exploring the ... [PAR] The baphomet is depicted as a female with two heads; one male, the other 
female ... in its belly and a fish tail; Wyvern: Flying serpent like a dragon, with two 
legs... [DOC] [TLE] wyverns - Memidex dictionary/thesaurus [PAR] a fire-breathing dragon used in medieval heraldry; had the head of a dragon and 
... a two legged dragon often represented in heraldry.