BRIEF REPORT Clinal Variation of Maxillary Sinus Volume in Japanese Macaques (Macaca fuscata)
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Macaques (genus Macaca) are unique among cercopithecids in that they possess a maxillary sinus, and among anthropoids in that they demonstrate a relatively weak relationship between the size of this sinus and the cranium. To test the hypothesis that extrinsic factors may contribute to maxillary sinus size variation, a sample of 46 Japanese macaque (M. fuscata) crania from known localities were subjected to computed tomography (CT) imaging, and sinus volume and nasal cavity area were analyzed relative to latitude and temperature variables. The results suggest that the environmental factors are significant determinants of nasal cavity size in Japanese macaques, but that the relationships between the environment and maxillary sinus volume (MSV) are probably a passive consequence of changes in the size of the nasal cavity. The sinus shrinks as the nasal cavity expands, due to an increased need to condition inspired air in colder climates. This in turn suggests that the sinus itself does not contribute significantly to upper respiratory function. Am. J. Primatol. 59:153–158, 2003. r 2003 Wiley-Liss, Inc.Keywords:
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Sinus (botany)
Bergmann's rule
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The extinct Diprotodon optatum was the largest ever marsupial, reaching over two tonnes. However, despite its large size, the cranium of Diprotodon is remarkably light, composed of thin bone and extensive endocranial sinuses. Cranial sinuses are air-filled cavities resulting from the resorption and deposition of bone through pneumatisation in response to biomechanical stress. Sinus morphology represents an optimisation between strength and weight reduction. The extraordinary preservation of the Diprotodon skulls found at Bacchus Marsh, southern Australia (37°40′S, 144°26′E), provides a unique opportunity to investigate hypotheses regarding the size and function of the atypically voluminous sinuses. Sinus function is difficult to test without first obtaining data on sinus variation within and between species. Therefore, the crania of Diprotodon and six species of extinct and extant vombatiform marsupials were studied using CT scans to provide a volumetric assessment of the brain endocast and cranial sinuses. Sinus volume scales positively and brain size scales negatively with skull size, so that larger species have relatively smaller brains and larger sinuses than those of smaller species. In the large, extinct palorchestid and diprotodontid marsupials the fronto-parietal sinuses expand around the dorsal and lateral regions of the braincase. The sinuses may have expanded in order to increase the surface area for attachment of the temporalis muscle, as the braincase itself would have provided insufficient surface area for the predicted muscle masses. Detailed three-dimensional reconstructions of the cranium, mandible and jaw adductor muscles were produced for Diprotodon and four extant marsupials (Vombatus ursinus, Phascolarctos cinereus, Macropus rufus and Wallabia bicolor) to investigate functional hypotheses using reverse engineering. Finite element analysis was used to identify areas of high and low stress, mechanical efficiency and bite performance in the crania of each species to investigate the relationship between biomechanical performance and diet. In addition, manipulations to the Diprotodon cranial model were performed to investigate changes in skull, and sinus structure (e.g. the normal model with fronto-parietal sinuses, a filled-sinus model, and a midsagittal crest model). Despite the apparent fragile nature of the cranium of Diprotodon, the model performed well and is relatively strong, indicated by low median stress levels through the model. The mechanical efficiency of the skull was also relatively high. The large cranial sinuses do not seem to disadvantage Diprotodon in terms of performance, and may in fact help to dissipate stress over the cranium. When examining the results from the manipulated models of Diprotodon, further evidence suggests that the normal model with sinuses may help to move stress away from the nasal and orbital regions of the cranium. The sinuses also allow the skull to be significantly lighter than if the frontal and parietal bones were not pneumatised. This study points to the significance of large sinuses in Diprotodon, and perhaps all marsupial megafauna, to reduce the weight of the skull while maintaining biomechanical performance.
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Abstract Macaques (genus Macaca ) are unique among cercopithecids in that they possess a maxillary sinus, and among anthropoids in that they demonstrate a relatively weak relationship between the size of this sinus and the cranium. To test the hypothesis that extrinsic factors may contribute to maxillary sinus size variation, a sample of 46 Japanese macaque ( M. fuscata ) crania from known localities were subjected to computed tomography (CT) imaging, and sinus volume and nasal cavity area were analyzed relative to latitude and temperature variables. The results suggest that the environmental factors are significant determinants of nasal cavity size in Japanese macaques, but that the relationships between the environment and maxillary sinus volume (MSV) are probably a passive consequence of changes in the size of the nasal cavity. The sinus shrinks as the nasal cavity expands, due to an increased need to condition inspired air in colder climates. This in turn suggests that the sinus itself does not contribute significantly to upper respiratory function. Am. J. Primatol. 59:153–158, 2003. © 2003 Wiley‐Liss, Inc.
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Internal nasal cavity morphology has long been thought to reflect respiratory pressures related to heating and humidifying inspired air. Yet, despite the widely recognized importance of ontogeny in understanding climatic and thermoregulatory adaptations, most research on nasal variation in modern and fossil humans focuses on static adult morphology. This study utilizes cross-sectional CT data of three morphologically distinct samples (African, European, Arctic) spanning from infancy to adulthood (total n = 321). Eighteen landmarks capturing external and internal regions of the face and nose were subjected to generalized Procrustes and form-space principal component analyses (separately conducted on global and individual samples) to ascertain when adult-specific nasal morphology emerges during ontogeny. Across the global sample, PC1 (67.18% of the variation) tracks age-related size changes regardless of ancestry, while PC2 (6.86%) differentiates between the ancestral groups irrespective of age. Growth curves tracking morphological changes by age-in-years indicate comparable growth trajectories across all three samples, with the majority of nasal size and shape established early in ontogeny (<5 years of age). Sex-based trends are also evident, with females exhibiting a more truncated growth period than males, particularly for nasal height dimensions. Differences are also evident between the anterior and posterior nose, with the height and breadth dimensions of the anterior nasal aperture and nasal cavity showing differential ontogenetic patterns compared to the choanae. Cumulatively, these results suggest that multiple selective pressures influence human nasal morphology through ontogenetic processes, including metabolic demands for sufficient oxygen intake and climatic demands for adequate intranasal air conditioning.
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ABSTRACT Variation in nasal floor topography has generated both neontological and paleontological interest. Three categories of nasal floor shape (Franciscus: J Hum Evol 44 (2003) 699–727) have been used when analyzing this trait in extant humans and fossil Homo : flat, sloped, and depressed (or “bi‐level”). Variation in the frequency of these configurations within and among extant and fossil humans has been well‐documented (Franciscus: J Hum Evol 44 (2003) 699–727; Wu et al.: Anthropol Sci 120 (2012) 217–226). However, variation in this trait in Homo has been observed primarily in adults, with comparatively small subadult sample sizes and/or large age gradients that may not sufficiently track key ontogenetic changes. In this study, we investigate the ontogeny of nasal floor shape in a relatively large cross‐sectional age sample of extant humans ( n = 382) ranging from 4.0 months fetal to 21 years post‐natal. Results indicate that no fetal or young infant individuals possess a depressed nasal floor, and that a depressed nasal floor, when present (ca. 21% of the sample), does not occur until 3.0 years postnatal. A canonical variates analysis of maxillary shape revealed that individuals with depressed nasal floors were also characterized by relatively taller anterior alveolar regions. This suggests that palate remodeling at about 3.0–3.5 years after birth, under the influence of tooth development, strongly influences nasal floor variation, and that various aspects of dental development, including larger crown/root size, may contribute to the development of a depressed nasal floor. These results in extant humans may help explain the high frequency of this trait found in Neandertal and other archaic Homo maxillae. Am J Phys Anthropol 155:369–378, 2014. © 2014 Wiley Periodicals, Inc.
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Abstract Several different factors have been hypothesized as explanations of variation in primate paranasal sinus size. Biomechanical forces, particularly those associated with mastication, are frequently evoked to account for differences in primate craniofacial pneumatization. To test whether masticatory stresses are responsible for maxillary sinus volume diversity, two platyrrhine species of the genus Cebus ( C. apella and C. albifrons ) were examined. The former has been identified as a hard object feeder, and many morphological differences between the two species are attributable to differences in the mechanical properties of their respective diets. Sinus volumes were derived from serial coronal CT scans of the crania of adults. Several external cranial measurements were used to scale sinus volume relative to the size of the face. Relative measures of maxillary sinus volume were compared using standard statistical techniques. In all comparisons, the two capuchin species do not differ from one another significantly at P < 0.05. Thus, this “natural experiment” fails to support the interpretation that biomechanical forces acting on the facial skeleton substantially affect the degree of paranasal pneumatization in primates. This result suggests that it is unlikely that the maxillary sinus performs any function in relation to masticatory stress; other factors must be responsible for the variation in sinus volume among primates. Anat Rec, 291:1414–1419, 2008. © 2008 Wiley‐Liss, Inc.
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Abstract The current study examines the frontal air sinus of the giraffe ( Giraffa camelopardalis ) cranium with the aim of evaluating previously offered hypotheses as to why they have such an atypically voluminous frontal sinus relative to other artiodactyls. To date, no quantification of the frontal sinus in the adult or developing giraffe has been undertaken or compared to other artiodactyl species. Crania from eight species of adult artiodactyls, and giraffes varying in age from newborn to adult, were studied using CT scans to provide a volumetric assessment of the frontal sinus. Sinus volume was strongly correlated to cranial mass in the male giraffe ontogenetic series. The adult giraffe of both sexes were found to possess a far larger than predicted sinus volume relative to the relationship between frontal sinus volume and cranial mass observed in the other adult artiodactyls. Our results suggest that the volume of the frontal sinus in the giraffe is likely to be unique among artiodactyls, and the potential function and evolution we consider in light of several previously articulated hypotheses. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.
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Abstract The frontal sinuses of bovid mammals display a great deal of diversity, which has been attributed to both phylogenetic and functional influences. In‐depth study of the hartebeest ( Alcelaphus buselaphus ), a large African antelope, reveals a number of previously undescribed details of frontal sinus morphology. In A. buselaphus , the frontal sinuses conform closely to the shape of the frontal bone, filling nearly the entire element. However, the horncores are never extensively pneumatized, contrasting with the condition seen in many other bovids. This evidence is inconsistent with the hypothesis that sinuses are opportunistic pneumatizing agents, suggesting that phylogenetic factors also play a role in determining sinus size. Both cranial sutures and neurovasculature appear to constrain the growth of sinuses in part. In turn, the sinus also affects the growth of the parietal; apparently this element is not truly pneumatized by the sinus in most cases, but the bone's shape changes under the influence of the sinus. Furthermore, the sinuses present relatively few struts when compared with the sinuses of some other bovids, such as Ovis . By adapting methods previously developed for measuring structural parameters of trabecular bone, it is possible to quantify certain aspects of sinus morphology. These include the number of bony struts within the sinus, the spacing of these struts, and the size of individual cavities within the sinus. Some differences in the number of struts are evident between subspecies. Similarly, significant differences occur in the relative number of struts between male and female A. buselaphus , which may be related to behavior. The volume of the sinus is strongly correlated with the size of the frontal, but less so with overall cranial size. This finding illustrates the importance of choosing variables carefully when comparing sinus sizes and growth between species. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
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Abstract The association between nasal shape, prognathism and the shape of the maxillary dental arch has been examined within samples of Negro and European skulls. Prognathism tends to be accompanied by an increasingly broad and short nose. Particularly high correlations exist between nasal height and the length of the cranial base and between nasal breadth and the distance which separates the upper canine teeth. Regression analysis has yielded quantitative estimates of the effect on a given dimension of variation in one or more of the others. It seems probable that both nasal shape and the maxillary dental arch‐prognathism complex may be subject to direct selection by environmental stress. The morphological association between these complexes suggests that a part of the interpopulation variation in prognathism may be a secondary effect of selection acting on the nose. Similarly, selection acting on the dental arch or maxilla could produce secondary changes in the nasal index (i.e. a non‐adaptive component of nasal variation).
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