Another member of the old guard is out at Merrill Lynch ( MER). The New York-based securities firm said Monday that Ahmass Fakahany, the 49-year-old co-president and chief operating officer, has decided to retire and will leave his position Friday. Fakahany, an ally of former chief Stan O'Neal, who left after billions of dollars' worth of writedowns, joined Merrill in 1987. His departure leaves Gregory Fleming as the sole president and COO under Chairman and CEO John Thain. "Upon my arrival, Ahmass informed me of his intention to transition out of Merrill Lynch in the first quarter and pursue other interests. He has been the consummate professional. He provided leadership during this challenging period and has transitioned the new team," Thain said in a statement. Prior to his role as co-president and COO, Fakahany was vice chairman and chief administrative officer from 2005 until he was appointed to his current role in May 2007. From 2002 to 2005, he was executive vice president and chief financial officer. Before that, he was chief operating officer of global markets and investment banking.