For years, David Lee Roth's hair has been as memorable as his outfits -- from the flowing mane of the multi-colored '80s to the parted look of his more recent cover-alls era. Not any more.

When Roth bounded on stage last night at the Forum in Los Angeles, as part of a huge guest-packed Foo Fighters concert celebrating Dave Grohl's birthday, he was shaved bald. The moment of discovery comes a few minutes into their raucous version of Van Halen's 'Panama,' embedded above, when Roth doffs his newsboy's cap.

Whoa, right? The Van Halen News Desk called it a "new bold look." (Check out additional photos of a shorn Roth from them right here.)

It's unclear when Roth decided on this new style. A Happy New Year message via his online Roth Show found him still sporting a full head of hair -- or, at least an approximation thereof. A surreal Christmas song he shared earlier in December didn't include any images of Roth.

For a time, speculation ran rampant on the state of his hairline, after a precipitous post-Van Halen recession. In fact, there's an entire message-board thread on the RothArmy.com website discussing how Roth's coif impacted 1988's 'Skyscraper.'

By 1994, Entertainment Weekly was noting that Roth's hair was "shorter and wispier, a shaggy bowl cut that hardly seems capable of billowing to its former Pacific heights." Into the 2000s, Roth was reportedly getting into a backstage brawl when touring mate (and Van Halen successor) Sammy Hagar made a quip about Roth being follically challenged.

You Think You Know Van Halen? 

See the Yearbook Photos of David Lee Roth and Other Rock Stars