One of Apollo Management's founders is cutting another tie to the storied private equity firm.

Michael Gross, who helped found the $13 billion private equity outfit Apollo, has resigned from his position as chairman of the board of Apollo Investment Management ( AINV), the firm said Monday. His resignation is effective immediately.

Apollo Investment is a publicly traded investment firm launched by the private equity firm in 2004. Gross was a senior partner with Apollo Management up until this past February.

"Mr. Gross advised the company that 'his resignation would allow him to better pursue other opportunities in the alternative asset arena,'" the release said.

In February, Gross surprised Wall Street, saying he was stepping down as chief executive of Apollo Investment to pursue "other opportunities in the alternative-asset arena.'' He wasn't out of the limelight for long. Shortly after, the corporate wheeler-dealer surfaced as the CEO and majority shareholder of Marathon Acquisition, a then 4-month-old company that's looking to cash in on Wall Street's renewed love affair with blank-check offerings

Gross has other commitments as well. He recently became co-chairman of the investment committee at Magnetar Capital, a startup fund run by Alec Litkowski from Citadel Investment Group and Ross Laser, formerly president of Glenwood Capital Management.

John J. Hannan, the chief executive officer of Apollo, "wished him well in his future endeavors."

Gross is the second executive to step down from Apollo Investment Management in the past month. Earlier in July, former South Dakota Senator Tom Daschle resigned as director of Apollo Investment. Daschle, a Democrat believed to be considering a run for president in 2008, resigned just three months after joining the company's board.