Len Wein, the influential comics writer who co-created Marvel’s Wolverine and DC’s Swamp Thing, and who helped revive the “X-Men” series in the 1970s, has died, his friends and industry colleagues said Sunday. He was 69.

The cause of death was not immediately known, but since March, his Twitter feed has detailed several health issues, including a spinal surgery and an abscess on his heel bone. His most recent surgery was Thursday, according to his feed, which included jokes wishing Wein had Wolverine’s quick-healing power.

Wein introduced Wolverine with artists John Romita Sr. and Herb Trimpe. The Canadian mutant debuted in “The Incredible Hulk” number 181.

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In 1975, he wrote and Dave Cockrum illustrated “Giant Size X-Men #1,” the first new X-Men story in five years, after the original team created by Stan Lee and Jack Kirby slipped from popular it y. The new series featured a new team including Wolverine, Nightcrawler, Storm and Colossus rescuing original X-Men Marvel Girl, Iceman and Angel, plus the recruits Havok and Polaris.

Today, the characters Wein introduced have helped bring in more than a billion dollars onscreen in the “X-Men” and “Wolverine” films. And Colossus was a key player in the breakout hit “Deadpool.”

In 1971, Wein and artist Bernie Wrightson also introduced Swamp Thing for DC Comics. He later edited 1980s Swamp Thing stories by Alan Moore, and edited Moore and artist Dave Gibbons’ celebrated, genre-bending “Watchmen.” Both “Swamp Thing” and “Watchmen” also led to film adaptations.

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In 2013, Wein talked to TheWrap about how much money he was paid for co-creating Wolverine, one of the most profitable creations in comics history. He said that while he initially received $15 to $20 for each page he wrote, he received a “not unreasonable” check for the film “The Wolverine,” in part because it was named for his character.

He said DC Comics, for which he created the Batman character Lucius Fox (played on film by Morgan Freeman), rewarded him generously.

“When I work for DC, anything I create I get a piece of,” said Wein. “Lucius Fox, for example, who was in the last trilogy of Batman movies played by Morgan Freeman, bought my new house. At Marvel, I did see a check off ‘The Wolverine,’ the current film. But as a rule I don’t any of the ancillary money off of all of the toys and soaps and shampoos and skateboards and God knows what else that features the character.”

He is survived by his wife, attorney Christine Valada, who provided many of the recent health updates on Wein’s Twitter feed.