New monkey genus
But genetic analysis at the Field Museum and the University of Alaska (by a guy I knew in college) confirmed that it was not just a new species, but a different genus than any known species.
These are exciting times to live in.
Update: In the comments, j.d. asks how often a new genus is described. As a mammalogist, I can only speak reliably for the roughly 5,000 species of mammals which are believed to exist.
A literature survey by Bruce Patterson of the Field Museum, published in 2000, found that, between 1992 and 1999, 7 new genera and 57 new species of mammals were described in the Neotropics (tropical South America). Other new species are being described from Asia and Africa. So, about one new genus of mammal from one continent, per year. And we know more about mammals than we do about most other major groups of metazoans. Rates of discovery among insects are several orders of magnitude higher.
For whatever reason, I've had February's discovery of the "Lost World" in New Guinea in my queue of interesting things to write about, and never quite knuckled down. On top of that I had a neat story about three new species of lemurs discovered in Madagascar.
The stories I don't have sitting in the queue because they never hit the press are the 8 mice and bats found in the average year in South America. They aren't sexy, they aren't fancy, and they are usually as much excitement to describe as they are a chore. Undescribed species will sit in jars for years waiting for someone to find time to write them up. They are all different, but it's hard to get a lot of excitement about another mouse with a slightly different skull.
It's humbling how little we know about the world right now, let alone what the world was like in the past. About a tenth of the world's species have been named, but the fact that a species is named just means that there's at least one specimen in a collection somewhere. What it eats, where it lives, how it sounds, how many offspring it has, how it attracts mates, what eats it, are all mysteries for most of the named species.
This has a couple of important consequences. First, it offers a host of ways to test evolution. Each species that we discover has the potential to break the pattern of hierarchies of morphology, geography and genetics which common descent would predict. Yet they don't. And as we add ecological data and behavioral data, we always come in with predictions that the species should be similar to the most closely related species. And that prediction works out nicely time and time again.
The other important lesson is that, while the species are often similar to ones we know about, they are different, and often different in interesting and unexpected ways. Learning about the diversity that exists within the primates tells us about ourselves and our ancestors, but understanding mice and how they handle different environments. There are lessons in those surveys for people who are willing to look for them. Lessons about how to survive in the tropics, lessons about how ecology, behavior and evolution interact, lessons about the underlying geology and the geological history of the earth. We learn about how life responded to previous bouts of climate change.
South America, Africa, Madagascar, the Philippines, and the other core centers of undiscovered biodiversity are also areas of rapid development and weak governments. That undiscovered diversity is disappearing faster than we can describe it for posterity. And that's a crying shame.