From Comic Alliance:
Andy Serkis has confirmed he is playing Ulysses Klaw in the upcoming Avengers Movie. This was kind of known for a while, especially after the trailer dropped showing a shadowed with claws (not Wolverine).
Well, I think I can absolutely confirm it’s Ulysses Klaw now because I think the news is out. I sort of noticed that people on the red carpets sort of knew that I was Ulysses Klaw, so I thought ‘It must be out then.’ It was [a really minimal role], but I just loved doing it. It’s a great character.
Ulysses Klaw first appears in Fantastic Four #53.