The dominant publisher of games on Facebook named David Ko, 41, a top executive overseeing mobile games, its new chief operations officer. The position had been vacant since August when John Schappert stepped down after the company missed earnings expectations for two consecutive quarters and its stock price fell precipitously.

Wehner, who has joined Facebook Inc as a vice president of corporate finance and business planning, oversaw Zynga's high-profile initial public offering last December, which priced shares at $10 and valued the company at $8.9 billion. Since then, shares have tumbled almost 80 percent as investors questioned the durability of Zynga's business as gamers seemed to tire of aging hits like "CityVille."

Zynga shares edged up slightly in extended trade, rising by 2 cents to $2.13.

As part of the shakeup, Mark Vranesh, 45, Zynga's top accounting executive, will replace Wehner as CFO, while Steven Chiang was named to oversee all game development, the company said.

In addition, Barry Cottle, a business and corporate development executive, was named chief revenue officer.

The new appointments were approved by Zynga's board on November 7, according to regulatory filings.

Zynga's new look at the top comes as CEO and founder Mark Pincus fights to turn around his faltering company and re-establish its once-golden status in Silicon Valley. The appointments were made on a permanent basis, the company said Tuesday, although the position vacated by marketing head Jeff Karp, who departed abruptly in September, remains unfilled.

Pincus sought to instill a sense of stability in a memo to employees released to the public on Tuesday.

"Mark, David, Barry and Steve are rooted in our culture, committed to our future and part of the talented bench of leadership at Zynga," Pincus said. "I'm confident we have the right team to deliver on our mission of connecting the world through games and position us for long-term growth."

Last month, the company sharply revised its full-year outlook and began layoffs after warning that its revenues were slowing as gamers left its once-popular titles published on the Facebook platform in droves.

The company has since begun cost-cutting measures, including layoffs, while Pincus vowed to personally supervise game development, which had been plagued by delays in the past year.

Wehner, whose last day at Zynga was Tuesday, will report to Facebook CFO David Ebersman at the Menlo Park-based social networking company, which has close ties to Zynga because it derives a significant percentage of its revenues from the game publisher.

Facebook said in a statement: "Dave's deep expertise in finance, strategy and corporate development will be a great addition to our team."

(Reporting By Gerry Shih; Editing by Steve Orlofsky, Bernard Orr)

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