Stone Poneys were a folk-rock trio formed in Los Angeles, consisting of Linda Ronstadt on vocals, Bobby Kimmel on rhythm guitar and vocals, and Kenny Edwards on lead guitar.
Ok, more accurately, the Stone Poneys brought Ronstadt into the limelight, and eventually Ronstadt’s backup band (different people) that toured with her became the Eagles.
https://www.billboard.com/articles/news/6844113/linda-ronstadt-glenn-frey-don-henley-eagles