Updated from 9:53 a.m. EDTMerck ( MRK) said Thursday that Raymond V. Gilmartin retired as chairman, chief executive and president, effective immediately, stepping down from the posts about 10 months before he had previously planned. Although Gilmartin, 64, had been scheduled to retire in March 2006, the timing of his departure was surprising, as was the choice of an insider to succeed him. Many analysts had expected Merck to choose someone outside the company. The new chief executive and president is Richard T. Clark, 59, who had been president of Merck's manufacturing division. The company won't choose a chairman for at least 12 to 18 months. The company's stock barely budged on the news, losing 2 cents to $34.91. Merck's board also announced that Lawrence A. Bossidy, a director, will become chairman of the board's newly constituted executive committee "which will work closely with Mr. Clark to provide support and continuity as he assumes his new duties." This three-member committee will remain in effect for one to two years. During that period, the board doesn't expect to select a chairman. Bossidy is a former chairman and CEO of Honeywell International ( HON). Gilmartin became Merck's CEO in June 1994 after serving as chairman and CEO of the medical device maker Becton Dickinson ( BDX). He will remain as a special adviser to the board's executive committee.