Callicebus, the titi monkey, is a South American or New World monkey. South American monkeys or platyrrhines comprise one of the two infraorders (Platyrrhini and Catarrhini) of anthropoid primates. They live exclusively in South and Central America, but their fossil distribution includes the Greater Antilles (MacPhee and Horovitz, 2002). The fossil record of platyrrhines extends back to the Deseadan or late Oligocene of Bolivia where they are represented by the genus Branisella (Takai and Anaya, 1996). Their presence in the New World is generally considered to be the result of a single dispersal event (Fleagle, 1999) near the end of the Eocene from the Old World, where all known basal anthropoids are found (Beard, 2002). Because South America was not connected with North America or Africa at the time, this dispersal must have involved rafting across some portion of the Atlantic.

Once in the New World, platyrrhines diverged into a variety of forms ranging in size from the smallest living anthropoid (Cebuella) at ~110 grams to the howler monkeys (Alouatta) that reach 11 kg (Fleagle, 1999). This diverse radiation of primates includes 78 living species (Fleagle, 1999) in 16 genera, one of which is the only living nocturnal anthropoid, Aotus. Their diets and locomotor adaptations are diverse, though most are at least partly frugivorous and none are primarily terrestrial.

Although the adaptations of different genera are reflected in their craniodental anatomy, platyrrhines in general retain a cranial morphology more similar to primitive anthropoids from the Eocene and Oligocene of Egypt such as Catopithecus, Parapithecus, and Aegyptopithecus than do the living Old World anthropoids (Fleagle, 1999; Simons, 2001). The research for which these CT data were collected indicates that this primitive anthropoid cranial morphology included considerable cranial pneumatization via the paranasal sinuses.

Callicebus moloch and C. torquatus are two of the larger species of titi monkeys. Both weigh around 1 kilogram, with males and females nearly equal in size (Fleagle, 1999). These monogamous and largely frugivorous monkeys live throughout Peru, Venezuela, Colombia, and Brazil (Fleagle, 1999). The precise phylogenetic position of Callicebus is uncertain but it is usually considered a close relative of Aotus (Ford, 1986), the Pitheciinae (Kay, 1994; Horovitz, 1999), or both (Rosenberger, 2002).

This male specimen, the skull of a juvenile (M1 not fully in place), was collected in Monte Bogato, Colombia. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning by Dr. James Rossie of Stony Brook University, courtesy of the Smithsonian Institution Division of Mammals. Scanning was funded by an NSF dissertation improvement grant to Mr. Rossie (#0100825). Funding for image processing was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Timothy Rowe of The University of Texas at Austin.

dorsal view

ventral view

This specimen was scanned by Matthew Colbert on 20 December 2001 along the coronal axis for a total of 328 slices. Each slice is 0.1449 mm thick, with an interslice spacing of 0.1449 mm and a field of reconstruction of 40.0 mm.

Literature
Beard, K. C. 2002. Basal anthropoids. In (W. C. Hartwig, Ed) The Primate Fossil Record, pp. 133-149. Cambridge, Cambridge University Press.

Fleagle, J. G. 1999. Primate Adaptation and Evolution. San Diego, Academic Press.

Ford, S. M. 1986. Systematics of the New World monkeys. In (D. R. Swindler & J. Erwin, Eds) Comparative Primate Biology, Vol. 1: Systematics, Evolution and Anatomy, pp. 73-135. New York, Alan R. Liss, Inc.

Horovitz, I. 1999. A phylogenetic study of living and fossil platyrrhines. American Museum Novitates 3269:1-40.

Kay, R. F. 1994. "Giant" tamarin from the Miocene of Columbia. Am J. Phys. Anthrop. 95, 333-353.

MacPhee, R. D. E. and I. Horovitz. 2002. Extinct Quaternary platyrrhines of the Greater Antilles and Brazil. In (W. C. Hartwig, Ed) The Primate Fossil Record, pp. 189-200. Cambridge, Cambridge University Press.

Rosenberger, A. L. 2002. Platyrrhine paleontology and systematics: The paradigm shifts. In (W. C. Hartwig, Ed) The Primate Fossil Record, pp. 151-159. Cambridge, Cambridge University Press.

Simons, E. L. 2001. The cranium of Parapithecus grangeri, an Egyptian Oligocene anthropoidean primate. Proceedings of the National Academy of Sciences, USA 98:7892-7897.

Takai, M. and F. Anaya. 1996. New specimens of the oldest fossil platyrrhine, Branisella boliviana, from Salla, Bolivia. American Journal of Physical Anthropology 99:301-317.

Links
Mammalian Species account of Callicebus moloch (American Society of Mammalogists)

Callicebus moloch on the Primate Info Net (University of Wisconsin, Madison)

Images of Callicebus on the Wisconsin Regional Primate Research Center website (University of Wisconsin, Madison)

Callicebus moloch on the Animal Diversity Web (University of Michigan Museum of Zoology)

Face slice movie: