McKayla Maroney competes on the vault during the Artistic Gymnastics Women's Vault final on Day 9 of the London 2012 Olympic Games at North Greenwich Arena on August 5, 2012. (Ronald Martinez/Getty Images)
LONDON -- Chinese Olympian Zou Kai won his fifth career gold medal Sunday, defending his title on floor exercise.
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He already had one gold from China's victory in the men's team competition last week, and has three more from the Beijing Games. He's got a chance to duplicate his Beijing three-peat on Tuesday, when he tries to defend his Olympic title on high bar.
All-around champion Kohei Uchimura of Japan won the silver medal and Russia's Denis Ablyazin took bronze.
American Jake Dalton finished fifth in the floor exercise.
Meanwhile, American McKayla Maroney competed in the vault final, but the world champion made a rare mistake: her feet skidded out from under her, and a look of shock crossed her face. The gold medal that everyone was certain was hers was gone.
This opened the door for Romania's Sandra Izbasa and she took advantage of it, winning the title on vault. Maroney claimed the silver medal, and looked downright surly as she stood on the medals podium.
Russia's Maria Paseka won the bronze.
Maroney was considered all but a lock for the gold medal, which would have given the U.S. women three in the first three gymnastics events. She won her world title last year by almost a half-point, and topped qualifying here by a similar margin. She was so impressive in Tuesday night's team final that U.S. coach John Geddert suggested they rename her vault "The Maroney."
"Man, that thing is a beast!" all-around champion Gabby Douglas said earlier Sunday. "How she gets that high, I'm so amazed. When she does it at camp, the table literally shakes."
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Her first vault was the Amanar -- a roundoff onto the takeoff board, back handspring onto the table and 2.5 twisting somersaults before landing -- and she did it better than the woman for whom it's named. She got such great height off the table the folks in the first few rows had to look up to see her, and her form was perfect in the air, legs pencil-straight, body tightly coiled.
She took a hop on her landing, and came down out of bounds. But even with that 0.3 deduction, she still scored 15.866, including a whopping 9.666 for execution.
Another vault like that, and the gold was hers.
But she appeared to land the second one on the back of her heels. Her feet slid forward and she dropped to the mat with a loud "plop!" The crowd gasped, and Maroney looked stunned. She's as consistent as a Swiss watch on vault, never making errors in training or in competition.
She scored just a 14.3, giving her an average of 15.083. Coach Arthur Akopyan tried to console her, but Maroney simply stared straight ahead, knowing her chance to add an individual gold to the one she won with the Fierce Five was gone.
Men's floor exercise final, men's pommel horse final and women's vault final all air in primetime Sunday.
(Nancy Armour, Associated Press)