Ari Up, frontwoman for pioneering British punk band the Slits, died Wednesday (Oct. 20), according to Sex Pistols' John Lydon (aka Johnny Rotten). Lydon, who is married to Forster's mother, delivered the news about the 48-year-old singer's death on his website.

"John and Nora have asked us to let everyone know that Nora's daughter Arianna (aka Ari-Up) died today (Wednesday, October 20th) after a serious illness," he wrote. "She will be sadly missed. Everyone at and PiLofficial.Com would like to pass on their heartfelt condolences to John, Nora and family. Rest in Peace."

Up, born Arianna Forster, formed the Slits in 1976 at the age of 14. The then all-female band set the mold for the early '90s riot grrrl movement and released two albums, 1979's 'Cut' -- which features an infamous cover photo of the topless band members covered in mud -- and 1981's 'Return of the Giant Slits,' before disbanding. Up later released her own solo effort and worked on various other projects before reforming the Slits in 2005.