The man-serpent is a monster, a serpent with a human face or head. In period, it usually had a woman’s head, as in the supporter of Graf von Cossentania, 1483, and as the crest of Walter Bonham, c.1547 [Dennys CoA]. While usually found guardant in mundane heraldry, it is nonetheless explicitly blazoned so; the illustration shows a man-serpent erect and guardant. See also serpent.
Lucien of Bath bears: Per chevron throughout Or and vert, two chaplets of thorn vert and a man-serpent erect guardant tail nowed Or faced proper crined gules.