Evolution of the nose and nasal skeleton in primates

Abstract

One traditional diagnostic feature of the Order Primates is a decreased emphasis on olfaction.1, 2 Some authors attribute this feature only to tarsiers and anthropoids, either through convergence or as a common feature of haplorhines.2–4 Other authors de‐emphasize olfaction relative to vision,5–7 which does not necessarily denote olfactory reduction per se. There are lengthy roots to this discussion. The importance of the sense of smell to at least some primates, humans in particular, has long been viewed as secondary to the importance of visual, auditory, and tactile senses. Smell, or olfaction, is viewed as the primitive special sense, the stimuli perceived in an unconscious manner, submerged relative to higher neural functions,1 and a sense that has been increasingly reduced during the course of primate evolution.1–8 Anatomical structures related to olfaction differ profoundly in proportions and complexity between higher taxonomic groups of primates (Haplorhini, Strepsirrhini). These anatomical differences are beyond dispute (Box 1). However, the relationship between the anatomical differences and primate sensory abilities, and hence the validity of using them to group primates into “microsmatic” or “macrosmatic” categories,9, 10 is less clear when we examine the physiological and genetic data on primate olfaction.

Distribution of Olfactory and Nonolfactory Surface Area in the Nasal Fossa of Microcebus murinus: Implications for Microcomputed Tomography and Airflow Studies

“…Primates are characterized by a reduction of the nasal fossa relative to other mammals, although the extent varies greatly across the order (Smith et al, 2007b). Because of varying degrees of orbital convergence toward the midline, the FR is nearly or completely obliterated in haplorhines (Cartmill, 1970;Smith et al, 2007b).…”

“…Because of varying degrees of orbital convergence toward the midline, the FR is nearly or completely obliterated in haplorhines (Cartmill, 1970;Smith et al, 2007b). It has been observed that the FR may also be somewhat ''compressed'' by enlarged orbits in at least some strepsirrhines compared with most other mammals (Smith and Rossie, 2008).…”

“…molecular weight and solubility) may deposit in different regions of the nasal passages, and that these regions of deposition appear to correspond to the zones of OR expression (Yang et al, 2007). Schoenfeld and Cleland (2005) suggest that this design, in which the (Smith et al, 2007b;Smith and Rossie, 2008). Unfortunately, knowledge of intranasal airflow in primates is heavily biased toward monkeys and humans, in which a relatively turbulent flow pattern predominates during sniffing behaviors, whereas airflow in rodent nasal fossae occurs in a laminar pattern (even during sniffing behaviors) which allows diffusion of odorants across peripheral spaces (Schoenfeld and Cleland, 2005).…”

Nasal Fossa of Mouse and Dwarf Lemurs (Primates, Cheirogaleidae)

“…FR, opening to frontal recess; I-IV, ethmoturbinals I through IV; MarT, marginoturbinal; MT, maxilloturbinal; N, nasal bone; ND, nasopharyngeal duct; NT, nasoturbinal; OR, olfactory recess; P, osseous palate; Pmx, premaxillary bone; SP, soft palate; TL, transverse lamina. Figure 1a the vomeronasal organ in Microcebus has been carefully described in previous publications (Schilling, 1970;Smith et al, 2007a), and will not be considered further.…”

“…In addition, the terminology used to describe structures varies greatly. These factors are limitations in the endeavor to understand functional specializations and the evolutionary modifications of the nasal fossa in different mammalian taxa, particularly in groups with highly diverse nasal morphology (Smith et al, 2004;Smith and Rossie, 2006;Smith et al, 2007a).…”