NEW YORK, May 18 (Reuters) - Principal Financial Group Inc. (PFG.N: Quote, Profile, Research), one of the biggest sellers of 401(k) retirement plans in the United States, on Thursday named Larry Zimpleman president and chief operating officer, effective June 1.

The Des Moines, Iowa-based financial services company said Zimpleman will oversee global and U.S. operations, including asset accumulation, Principal Bank, life and health insurance and asset management. He will join the company's board of directors. Chairman and Chief Executive J. Barry Griswell will oversee strategy, merger activity and corporate functions.

Zimpleman has worked for Principal since 1971, rising to become president of retirement and investor services in 2003.

Separately, Principal named Daniel Houston executive vice president, overseeing the full-service pension business and retirement distribution. He joined the company in 1984.

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