Multiple new species of large, living mammal (part III)

Yet more on the multiple new Amazonian mammals that have been discovered or documented by Marc van Roosmalen. If you haven't already done so, please read part I and part II. Here in part III we're going to look at the monkeys, as Marc has continued to discover various forms that don't match any documented species...

They include a new grey saki (pictured at left: it is larger with longer fur and a less pronounced face than the only similar species, Pithecia irrorata), a new black saki (Chiropotes), and several new spider monkeys, including the Rio Purús black spider monkey, Silvery bellied spider monkey, Upper Xingú white-cheeked spider monkey and Long-limbed black spider monkey. The latter species, notable for its large jaws and canines, was first mentioned in Cruz Lima's 1945 Mammals of Amazonia but has since gone unstudied and been taxonomically neglected (a dangerous thing when populations are small: Daugherty et al. 1990). The spider monkeys are mostly distinguished from recognised taxa on the basis of differences in fur and skin pigmentation, and they also exhibit distinct ranges and habitats. Authors differ in whether they regard the different spider monkey taxa as species or subspecies, on which read on...

Three new woolly monkeys (Lagothrix) are also among the potential new species. The first, the Orange woolly monkey [depicted in adjacent image], has already been both depicted in the literature (a picture of one is included in, again, Cruz Lima's 1945 Mammals of Amazonia) and deposited within a museum collection (Marc found one, collected in 1935, in the collection of the Museu Paraense Emilio Goeldi in Pará). The second, the Fair-haired woolly monkey [depicted below at left], has also been recorded before, but individuals have been assumed to be unusually light-coloured variants of the Common or Humboldt's woolly monkey L. lagothricha. Marc's new data indicates that this is in fact a good species with a unique pigmentation (and not just restricted to the body pelage, but referring also to skin colour and facial hair). Phylogenetic analysis of DNA recovered from dung has shown that it is more closely related to Poeppig's woolly monkey L. poeppigii [itself regarded by some workers as a subspecies of L. lagothricha rather than as a species] than to the Common woolly monkey, which is interesting as Poeppig's woolly monkey is dark brown.

The third possible new species is an entirely black member of the genus that differs in social structure, habitat choice and other behavioural features from other woolly monkey species. As with the dwarf tapir and some of the other new taxa that are under investigation, the black woolly monkey is hypothesised to be an old endemic of the east side of the Aripuanã River: when, more recently, this area was invaded by Geoffroy's woolly monkey L. cana, the two species had already diverged enough to prevent inbreeding and they now occur sympatrically.

Note that recent taxonomic revisions have - as with so many primate genera - raised the number of recognised woolly monkey species. The conventional view (e.g., Emmons 1997, Nowak 1999, Janson 2001) has been that Lagothrix includes only the Common or Humboldt's woolly monkey L. lagothricha and the Yellow-tailed woolly monkey L. flavicauda. The latter species is very poorly known, and was thought extinct until its rediscovery in 1974 (Mittermeier et al. 1975). Recent revisions have led to a revival of the old idea (first mooted by Oldfield Thomas in 1927) that the Yellow-tailed woolly monkey deserves its own genus, Oreonax (Groves 2001, DeLuycker 2007). Meanwhile, Lagothrix proper includes not only L. lagothricha, but also Geoffroy's or the Grey woolly monkey L. cana, Colombian woolly monkey L. lugens and Poeppig's woolly monkey L. poeppigii.

As with most cases where former subspecies have been raised to species rank, not all workers within the field agree with the idea that the taxa concerned really warrant species-level distinction. The dirty little secret of biology is that - given the fact of evolution - species are merely arbitrarily designated segments of phylogenetic lineages. If a population differs enough from others (in either, or both, morphology or/and genetics) to warrant recognition, some argue that it should be a 'species' (though I'm not prepared to go as far as endorsing the LITU* concept). We should at least be consistent, and give species status to those new taxa that differ from other species as much as do long-recognised species. Furthermore - at the risk of treading on very dangerous ground - I will note that it is always easier to drum up media interest and political will when species are involved, and the same is not the case when the taxa in question are mere subspecies. Anyway, if Marc's interpretation of the data is correct, Lagothrix is substantially more diverse than presently recognised, and that applies even if some of these new animals are regarded as subspecies [adjacent image shows Long-limbed black spider monkey].

* Least Inclusive Taxonomic Unit

This isn't it among the monkeys. As you can see on the website, Marc also seems to have new tamarins, an additional saki, new titi monkeys, a new squirrel monkey and a new uacari. I won't cover all of these here, but perhaps the most interesting story is that behind a tamarin that Marc is calling Cruz Lima's saddleback tamarin. First illustrated by Emílio Goeldi in 1907 for an unpublished manuscript, it was (like the Long-limbed black spider monkey and Orange woolly monkey) later depicted in Cruz Lima's Mammals of Amazonia, published in 1945, and regarded as a juvenile Weddell's saddleback tamarin Saguinus fuscicollis weddelli. Hershkovitz (1977) later named it as a distinct subspecies. In 2002, Tomas van Roosmalen made the first recorded observation of a wild group of this kind of tamarin. Based on morphological characters and other details, Marc thinks that it is a distinct species, most closely related to Weddell's saddleback tamarin.

And more to come in part IV.

Refs - -

Daugherty, C. H., Cree, A., Hay, J. M. & Thompson, M. B. 1990. Neglected taxonomy and continuing extinctions of tuatara (Sphenodon). Nature 347, 177-179.

DeLuycker, A. M. 2007. Notes on the Yellow-tailed woolly monkey (Oreonax flavicauda) and its status in the protected forest of Alto Mayo, northern Peru. Primate Conservation 22 (free pdf here).

Emmons, L. H. 1999. Neotropical Rainforest Mammals: A Field Guide (Second Edition). University of Chicago Press, Chicago & London.

Groves, C. P. 2001. Primate Taxonomy. Smithsonian Institution Press, Washington D.C.

Hershkovitz, P. 1977. Living New World Monkeys (Platyrrhini): With an Introduction to Primates, Vol. 1. The University of Chicago Press, Chicago.

Janson, C. H. 2001. Capuchin-like monkeys. In Macdonald, D. (ed) The New Encyclopedia of Mammals. Oxford University Press, pp. 344-353.

Mittermeier, R. A., de Macedo Ruiz, H. & Luscombe, A. 1975. A woolly monkey rediscovered in Peru. Oryx 13 (1), 41-46.

Nowak, R. M. 1999. Walker's Mammals of the World, Sixth Edition (two volumes). The Johns Hopkins University Press, Baltimore and London.