Roman Fountain Monster

I found this fantastic piece of ancient sculpture on the Via Della Conciliazione, not far from St. Peter's Square in Rome. I've always wondered how old this fierce monster is, and who created him. It was a magical meeting, and I hope he's still there, as he has been through the ages, guarding the water fountain.

"Standard belief has it that the origin of the spa dates back to the Roman era, when troopers of their legions fatigued by wars, would take to rejuvenation, relaxation and treatment of sore wounds through water. Hot, natural spring water was considered to be the best cure for wounds and tired muscles. The legionnaires, hence, started building baths around naturally found hot water springs or hot water wells. These baths were popularly called ‘aquae’, while the treatments undertaken at these aquae were known as ‘Sanus per Aquam’ – of that SPA is taken into account to be an acronym – which means health by or through water. "
From https://thermalsprings.wordpress.com/ancient-thermal-baths-and-spa/origin-of-spa/