Stars are making dramatic exits in gowns with enticing rear views. Keisha Whitaker showed some skin in a backless number with sculpted floral beading. Jennifer Lopez played up her shoulder blades with peek-a-boo crystal strands. Portia de Rossi wore a Zac Posen gown that combined a slinky halter neck with a “fringe dressage braid” reminiscent of the braided manes worn by dressage riding horses. Posen says the design was inspired by style touchstones of the 1930s: “deco futurism, Claridges [Hotel], Billy Baldwin and John Bouvier.” In the case of de Rossi’s gown, as with Brittany Murphy’s fin de siècle-inspired Roberto Cavalli, the look is as intellectual as it is sexy. As Posen says of his design, “The glamour is avant-garde.”

—Betony Toht