The more I search, the more Ideas I get! another link on Medusa and her appearance. This says pretty much what the other say with the addition of:
* Black tongue that was too big for her mouth
*Previously she was portrayed in several ways – as a winged horse like Pegasus, as a “woman with equine hindquarters and wings in her hair” and then later, after seeing some portraits of her, the current idea of a reptilian snake haired, scaley clawed woman.