Emeryville-based art e-commerce retailer Art.com said Monday that it has acquired Zenfolio, the operator of a website aimed at helping professional and amateur photographers to sell and market their photos and services. Financial terms of the buy were not disclosed. Zenfolio was founde din 2006, and was founded and headed by Alex Peyzner. The two said they will continue to operate as separate, stand-alone sites. Zenfolio was based in Menlo Park.