Mark Volman, a founding member of the ’60s pop-rock group The Turtles, has died at age 78.

In a statement shared on Facebook, Volman’s lawyer Evan Cohen confirmed that the singer had died. “I am sorry to report that my long-time friend and client, Mark Volman of The Turtles and Flo & Eddie (and a couple of years in the Mothers of Invention), has died at the age of 78,” he wrote. “Mark and bandmate Howard Kaylan stepped up and set an example for decades, standing up for the rights of musicians in various legal actions, which had a great impact on the progression of the law in several different areas (including sampling, and the eventual protection of 60s recordings under the Music Modernization Act).”

In 2020, Volman confirmed in an interview with People that he had been diagnosed with Lewy body dementia, and opened up about how he was living with the disease. “I got hit by the knowledge that this was going to create a whole new part of my life,” he said at the time. “And I said, ‘OK, whatever’s going to happen will happen, but I’ll go as far as I can.’”

Alongside fellow band founder Howard Kaylan, Volman helped lead The Turtles through a prosperous career in the late 1960s, where the band released a number of hits. Over the course of the band’s career, they notched 17 career entries on the Billboard Hot 100 and earned five top 10 hits.

“Happy Together,” widely considered to be the band’s signature song, was their sole No. 1 hit on the chart, spending three weeks at the summit in 1967. The band famously earned their first chart entry with a cover of Bob Dylan’s “It Ain’t Me Babe,” which also went on to be their first top 10 hit after it peaked at No. 8 on the chart in 1965.

“Happy Together” was voted into the Grammy Hall of Fame in 2007. The band’s other top 10 hits on the Hot 100 were “She’d Rather Be With Me,” “Elenore” and “You Showed Me.” The group reached the top 10 on the Billboard 200 in February 1968 with The Turtles! Golden Hits.