Bruce Wasserstein, the legendary Wall Street deal maker identified with an era of no-holds-barred takeover battles, has died at the age of 61. His death leaves major questions about the future direction and leadership of Lazard Ltd., the investment bank he headed.

Wasserstein, a star investment banker since the 1970s, was credited with brokering more than 1,000 transactions worth more than $250 billion, including Time's merger with Warner Brothers and the Dean Witter, Discover & Co combination with Morgan Stanley. He invented takeover defenses and was not scared of extremely adversarial deals.

He was a great tactician, said Felix Rohatyn, former Lazard executive who knew Wasserstein for four decades. He was extremely smart. He scared people actually.

It is always very difficult to replace somebody who plays such an important role in the life of a company, he added.

The company had announced on Sunday that Wasserstein, 61, had been hospitalized for an irregular heartbeat and his condition was serious, but he was stable and recovering. On Wednesday, the company said the cause of death had not yet been determined.

Wasserstein joined Lazard in 2002 and was charged with cleaning up the messy partnership and taking it public. He will be succeeded as chief executive in the interim by Steven Golub, vice chairman of the company, Lazard said on Wednesday.

He has some pretty big shoes to fill, said Anton Schutz, the president of Mendon Capital Advisors, which owns Lazard shares.

Lazard's shares were suspended before the close, ahead of the confirmation of his death. Shares have traded lower in the past week after rumors about Wasserstein being ill.

Wasserstein's death comes nearly four years after that of his playwright sister, Wendy, whose fame in the entertainment world could be said to equal his in finance. A Pulitzer Prize and Tony Award winner, she died of cancer in 2006 at age 55.

THE DEALMAKER

Wasserstein, known as Bid 'em up Bruce -- a nickname he despised -- had been involved in one of the year's biggest potential deals, advising Kraft Foods in its proposed takeover of U.K. candy maker Cadbury.

The Wall Street veteran achieved fame as an adviser to buyout house KKR on its unprecedented acquisition of RJR Nabisco in 1989, which was recorded for posterity in the book, Barbarians at the Gate, by Bryan Burrough and John Helyar.

Bruce Wasserstein was a titan of a legendary age in Wall Street history, when investment bankers during the 1980s seemed to be able to guide the fates -- the lives and deaths of many, many large American corporations, Burrough told Reuters. He was the biggest and the best, and he probably would have told you so.

Until a few years ago, the RJR takeover was the largest leveraged buyout in history.

Over the years, Wasserstein earned a reputation as a brilliant but hard-nosed banker who always found a way to get deals done.

Among other techniques, Wasserstein invented the Pac-Man defense where a takeover target turns and buys its would-be acquirer.

Activist investor Carl Icahn called him a a good friend and a smart guy.

I respected him, Icahn said. He was one of the few really smart guys on Wall Street.

William Cohan, author of the Lazard history The Last Tycoons said: Bruce always found a way to make money and come up smelling like a rose. He will go down as one of the most innovative, albeit flawed leaders in Wall Street history. Yet toward the end, despite himself, he evolved into a statesman for the industry.

There were essentially three stages to Wasserstein's career-- working at First Boston, co-founding his own firm and selling it to Dresdner Bank, and then moving to Lazard and helping it go public.

He earned a degree from the University of Michigan and then enrolling in Harvard Law at age 19. In 1970, he graduated from Harvard Law and a year later, received his Harvard MBA. He also attended the London School of Economics and went to Cambridge University as a Knox Traveling Fellow.

He worked briefly as a volunteer for consumer advocate Ralph Nader while he was in law school.

After graduation, Wasserstein joined elite law firm Cravath, Swaine & Moore. But he soon traded life at the white-shoe law firm for the faster pace of Wall Street.

He joined investment bank First Boston Corp in 1977, where he and Joseph Perella, another top Wall Street banker, built an M&A practice. The two left to form their own bank, Wasserstein Perella & Co, in 1988.

Perella, his partner for 16 years, called Wasserstein a rare talent, noting, this is a great loss for Wall Street, in a statement.

In 2000, Wasserstein sold Wasserstein Perella & Co to Germany's Dresdner Bank for $1.5 billion.

When plans for an investment banking unit spin-off failed a year later, he quit and left the firm bearing his name. In time, some of the people he recruited to Dresdner also left.

Wasserstein joined Lazard in 2002, where he was credited with breaking down territorial walls and helping it go public.

Outside Wall Street, Wasserstein's favorite pursuit was journalism. The one-time college newspaper editor and summer staffer at Forbes magazine acquired New York magazine through his $2 billion private investment firm, Wasserstein & Co.

He also wrote business-related books.

Wasserstein's private equity fund also owns The Deal LLC, a media company focused on the mergers and acquisitions market.

(Reporting by Steve Eder, Paritosh Bansal, Dan Wilchins, Joseph Giannone and Anupreeta Das in New York; Jessica Hall in Philadelphia; and Svea Herbst in Boston. Editing by Steve Orlofsky, Ted Kerr and Carol Bishopric)

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