Multiple-author post delegation tool?

I’m currently writing for a news outlet that uses WordPress as our CMS. There are multiple authors (about 15) and we have large email lists that we use to update each other on press releases the team receives, as well as interesting news to repost that we see on other news sites. Sometimes the lists get overwhelming, and people claim articles that other people have already claimed, which results in similar news stories on the blog.

What I’m looking for is a plugin where an admin can post news stories that need to be written that day, and then authors can claim stories for writing later. I’ve been doing searching, but haven’t been able to find anything, and I’d like some suggestions before I resort to writing my own plugin.

Is there anything available already that I’ve missed?

Thanks for your help 🙂