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Jennifer Lopez was a dancing queen on New Year's Eve.

The pop sensation rang in the New Year in Las Vegas, performing at a semi-private concert at Caesars Palace's famous Colosseum. But it was the dancing that really stole the show during her 90-minute performance.

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"I'm so grateful to be up here on this stage tonight," she said in between booty-popping and tangoing and every other dance you can think of. "I love spending these moments with you guys." was there to see the show, watching J.Lo sing out many of the hits from her storied career. But what's more than that, also go to see Jen's insane body, as more than a few of her songs involved skimpy outfits that showed off her toned physique.

Mama's got it going on!

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As the clock struck midnight, J.Lo broke out in Charlie Chaplin's "Smile" before leading a frantic countdown (as she seemed to have lost track of the seconds while singing.)

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Speaking of 2015, she said, "I can't think of a better way to start it than with a smile."

Here, here, J.Lo!