The Flyers confirmed the news Monday. Lonsberry was 67.
"My thoughts and prayers go out to Ross' wife, Juanita, and the Lonsberry family," Flyers chairman Ed Snider said. "Ross played six and a half seasons with the Philadelphia Flyers, including our Stanley Cup teams. He was a hard-hitting, two-way player who contributed greatly to our success. I have very fond memories of Ross as a player and a friend, and he will sorely be missed."
Lonsberry played for Hall of Fame coach Fred Shero during the championship seasons in the '70s, serving primarily as a defensive forward on the team's second line with Rick MacLeish and Gary Dornhoefer. He scored 32 goals for the Flyers in 1973-74. He had four goals and 13 points in 17 games in the Stanley Cup Playoffs in 1974 when the organization won its first Stanley Cup.
He finished his career with 256 goals, 310 assists and 566 points in 968 games spanning 15 seasons with the Boston Bruins, Los Angeles Kings, Flyers and Pittsburgh Penguins. He had 21 goals and 25 assists in 100 career playoff games.
Lonsberry was traded by the Flyers to the Penguins in 1978 and he spent the final three years of his career in Pittsburgh before retiring in 1981.