Kay, R. F., V. M. Campbell, J. B. Rossie, M. W. Colbert, and T. B. Rowe. 2004. Olfactory fossa of Tremacebus harringtoni (Platyrrhini, Early Miocene, Sacanana, Argentina): implications for activity pattern. Anatomical Record, Part A, 281A:1157-1172.

CT imaging was undertaken on the skull of ~20 Myr-old Miocene Tremacebus harringtoni. Here we report our observations on the relative size of the olfactory fossa and its implications for the behavior of Tremacebus. The endocranial surface of Tremacebus is incomplete making precise estimate of brain-size and olfactory fossa-size imprecise. However, olfactory fossa breadth and maximum endocranial breadth measured from CT images of one catarrhine and eight platyrrhines for which volumes of the olfactory bulb and brain are known show that the osteological proxies give a reasonably accurate indication of relative olfactory bulb size. Aotus has the largest relative olfactory fossa breadth and the largest olfactory bulb volume compared to brain volume among anthropoids. Tremacebus had a much smaller olfactory fossa breadth and, by inference, bulb volume--within the range of our sample of diurnal anthropoids. Variations in the relative size of the olfactory bulbs in platyrrhines appear to relate to the importance of olfaction in daily behaviors. Aotus has the largest olfactory bulbs among platyrrhines and relies more on olfactory cues when foraging than Cebus, Callicebus, or Saguinus (Bolen and Green, 1997; Bicca-Marques and Garber, 2004). As in other examples of nocturnal versus diurnal primates, nocturnality may have been the environmental factor that selected for this difference in Aotus, (Barton et al., 1995), although communication and other behaviors are also likely to select for olfactory variation in diurnal anthropoids. Considering the olfactory fossa size of Tremacebus, olfactory ability of this Miocene monkey was probably not as sensitive as in Aotus and counts against the hypothesis that Tremacebus was nocturnal. This finding accords well with previous observations that the orbits of Tremacebus are not as large as nocturnal Aotus (Kay and Kirk, 2000).

This specimen, the holotye of Tremacebus harringtoni consists of a partial skull received by Carlos Rusconi in 1932 from Sr. Thomás Harrington who collected it from the Early Miocene (~22 MA, Colhuehuapian SALMA) from approximately 12 km southwest of Cerro Sacanana, in northcentral Chubut Province, Argentina.

Rusconi named the specimen as a species of Homunculus (Rusconi, 1933), and provided an extended description of the fossil (Rusconi, 1935). Philip Hershkovitz (1974) proposed a new genus for this skull. At some point after Rusconi’s original description, a substantial amount of plaster was added to reconstruct missing parts. Later, Hershkovitz and others made an effort to have the plaster removed but succeeded only partially because the plaster is cleverly tinted to match the color of the fossil bone. In an effort to determine more precisely the limits of bone, matrix, and plaster, and to better appreciate the structural details of the interior of the skull, Richard Kay borrowed the specimen from Dr. Jaime Powell, curator of the Rusconi Collection at Museo de Fundación Miguel Lillo, Tucuman, for CT scanning. Details of the preservation provided by Hershkovitz (1974) are substantially correct except that the apex of the orbit and optic foramen are not preserved as Hershkovitz claimed, and the lateral pterygoid plate figured by Hershkovitz consists of plaster. Hershkovitz’s claim that there was a large inferior orbital fissure in life cannot be confirmed.

The specimen was scanned by Matthew Colbert on 12 November 2002 along the coronal axis for a total of 1177 slices, each slice 0.0466 mm thick, with an interslice spacing of 0.0466 mm.

Literature

Baron, G., H. D. Frahm, K. P. Bhatnagar, and H. Stephan. 1983. Comparison of brain structure volumes in Insectivora and Primates. III. Main olfactory bulb (MOB). Journal für Hirnforschung 24:551-558.

Barton, R. A., A. Purvis, and P. H. Harvey. 1995. Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores. Philosophical Transactions: Biological Sciences 348:381-392.

Cartmill, M. 1980. Morphology, function and evolution of the anthropoid postorbital septum; p 243-274 in R. Ciochon, B. Chiarelli (eds.), Evolutionary Biology of the New World Monkeys and Continental Drift. Plenum Press, New York.

Cave, A. J. E. 1973. The primate nasal fossa. Biological Journal of the Linnean Society 5:377-387.

Doving, K. B., and D. Troiter. 1998. Structure and function of the vomeronasal organ. Journal of Experimental Biology 201:2913-2925.

Firestein, S. 2001. How the olfactory system makes sense of scents. Nature 41:211-218.

Frahm, H. D., H. Stephan, and G. Baron. 1984. Comparison of brain structure volumes in Insectivora and Primates. V. Area striata. Journal für Hirnforschung 25:537-557.

Hershkovitz, P. 1974. A new genus of late Oligocene monkey (Cebidae, Platyrrhini) with notes on postorbital closure and platyrrhine evolution. Folia Primatologica 21:1-35.

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

Kay, R. F. 1990. The phyletic relationships of extant and fossil Pitheciinae (Platyrrhini, Anthropoidea). Journal of Human Evolution 19:175-208.

Kay, R. F., and E. C. Kirk. 2000. Ostological evidence for the evolution of activity pattern and visual acuity in primates. American Journal of Physical Anthropology 113:235-262.

Kay, R. F., V. M. Campbell, J. B. Rossie, M. W. Colbert, and T. B. Rowe. 2004. Olfactory fossa of Tremacebus harringtoni (Platyrrhini, Early Miocene, Sacanana, Argentina): implications for activity pattern. Anatomical Record, Part A, 281A:1157-1172.

Keverne, E. B. 1999. The vomeronasal organ. Science 286:716-720.

Kirk, E. C., and R. F. Kay. 2004. The evolution of high visual acuity in the Anthropoidea; p 539-602 in C. F. Ross and R. F. Kay (eds), Anthropoid Origins: New Visions. Kluwer/Plenum Publishing, New York.

Koppe, T., H. Nagai, and T. C. Rae. 1999. Factors in the evolution of the primate pneumatic cavities: possible roles of the paranasal sinuses; pp. 151-175 in T. Koppe, H. Nagi, and K. W. Alt (eds), The Paranasal Sinuses of Higher Primates. Quintessence Publ. Co. Inc., Chicago, Illinois.

Luchterhand, K., R. F. Kay, and R. H. Madden. 1986. Mohanamico hershkovitzi, gen et sp. nov., un primate du Miocène moyen d'Amérique du Sud. Comptes Rendus de l'Academie des Sciences, Paris 303(Ser. II):1753-1758.

Martin, R. D. 1973. Comparative anatomy and primate systematics. Symposium of the Zoological Society (London) 33:301-337.

Rossie, J. B. 2003. Ontogeny, homology, and phylogenetic significance of anthropoid paranasal sinuses. in Anthropology. Yale University, New Haven, CT.

Rusconi, C. 1933. Nuevos restos de monos fósiles del Terciario antiguo de la Patagonia. Anales de la Sociedad Científca Argentina 116:286-289.

Rusconi, C. 1935. Las especies de primates del oligoceno de Patagonia (gen. Homunculus). Revista Argentina de Paleontolia y Anthropolia 1:39-68 71-100.

Setoguchi, T., and A. L. Rosenberger. 1987. A fossil owl monkey from La Venta, Colombia. Nature 326:692-694.

Smith, T. D., M. I. Siegel, and K. P. Bhatnagar. 2001. Reappraisal of the vomeronasal system of catarrhine primates: ontogeny, morphology, functionality and persisting questions. Anatomical Record 265:176-192.

Stephan, H., H. D. Frahm, and G. Baron. 1981. New and revised data on volumes of brain structures in insectivores and primates. Folia Primatologica 35:1-29.

Stephan, H., H. D. Frahm, and G. Baron. 1984. Comparison of brain structure volumes in primates. VI: non-cortical visual structures. Journal für Hirnforschung 25:385-403.

Szalay, F. S., and E. Delson. 1979. Evolutionary History of the Primates. Academic Press, New York, 580 pp.

Van Valkenburgh, B., J. Theodor, A. Friscia, and T. Rowe. in press. Respiratory turbinates of Canids and Felids: A Quantitative Comparison. Journal of Morphology.

Wright, P. C. 1996. The neotropical primate adaptation to nocturnality: feeding in the night (Aotus nigriceps and A. azarae); pp. 369-382 in N. Norconk, A. L. Rosenberger, and P. Garber (eds), Adaptive Radiations of Neotropical Primates. Plenum Press, New York.

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