These are just guesses, but I think it's a Spix's, but it could also be a Geoffroy's. Other suggestions are welcome . devilfish, you wouldn't happen to have any more photos of this animal?
Based on ISIS listings, and some photos I'd seen, I initially thought it might be a Spix's but was not fully convinced. I guess it may just be a generic/hybrid listed on ISIS without subspecific status. Attached are a few other photos of the same animal - one also shows its cage-mate.
Just put one of my more nerdy Christmas presents to use (this: [ame=http://www.amazon.co.uk/Marmosets-Tamarins-Conservation-International-Pocket/dp/1934151203/ref=sr_1_1?ie=UTF8&qid=1296940594&sr=8-1]Marmosets and Tamarins Conservation International Pocket Guide Series: Amazon.co.uk: A Rylands, RA Mittermeier, AF Coimbra-Filho, EW Heymann, Stephen D Nash: Books[/ame] - thanks to robmv for calling my attention to it!). I'd agree with Spix's Saddleback (S. f. fuscicollis) going by the light-coloured head (although the fur looks a bit patchy, which might be confusing the issue).
It's not really a book as such, it's a fold-out chart, but it's superb, particularly given its low cover price. 61 different taxa in really nice clear images and all with range maps - and (nerdish joy) a ticklist in the back. Many of the species listed I've never seen images of before - things like Aripuana Marmoset and Mottled-faced Tamarin. Big thumbs up from me.
Thanks for adding the photos devilfish. It does look most like a Spix's. And Maguri, that sounds like an exellent christmas present! Thanks for using it.
