A significant development for Boston’s venture capital market.

Boston-area venture capitalist Ryan Moore has agreed to join Atlas Venture as a partner, Fortune has learned. He had spent the past 12 years with GrandBanks Capital, where his deals have included Enpocket (sold to Nokia), GlassHouse Technologies (in registration for an IPO) and Vivox.

This is a significant move for a number of reasons. So I’m going to list them in no particular order:

1. It’s about damn time. For the past several years, Moore’s name has come up in virtually every conversation I’ve had with VC headhunters. He’s turned down offer after offer, but finally decided it was time to move onto a larger platform — particularly one that already employs his long-time friend Jeff Fagnan (they are both branches off the old Softbank tree, as is Grandbanks founder Charley Lax).

2. Moore staying in Boston is a vote of confidence for the local market. He could have gone to Silicon Valley, where he once lived, but chose to stick around (even though Marc Andreessen wrongly asserts that “a massive brain drain from Boston to the Valley, which has all but gutted Boston as a place for high-tech entrepreneurship.”).

3. This is yet another indication that Atlas Venture is on the road to recovery. It was less than three years ago that the firm managed to raise barely half of the $500 million it was seeking for its eighth fund, and jettisoned a number of partners. Atlas wasn’t yet part of the walking dead, but it was a future candidate. Adding another young up-and-comer like Moore will help keep the zombies away, although the ultimate measure will continue to be returns.

4. Speaking of change at Atlas, Moore’s arrival will coincide with longtime partner Axel Bichara transitioning into a venture partner role. Kind of like what Chris Spray quietly did earlier this year. That means three active IT partners and three active life sciences partners.

5. For Grandbanks, this is obviously problematic. The firm is only around 43% committed on its current $86 million fund, but Moore was one of just three general partners — and had been around since the firm’s formation. Existing GrandBanks staff will take over Moore’s board seat responsibilities — including GlassHouse Technologies, which is about to embark on its IPO roadshow (if it doesn’t get acquired first). Charley Lax will take over that board seat, according to a letter sent yesterday to GrandBanks LPs (in which Lax repeatedly lauded Moore). Expect the firm to seek new staff as soon as possible.

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