Allometric relations of teeth and jaws in man

Static adult intraspecific allometry of jaws and teeth was investigated in a sample of 100 Negro crania. The relations between tooth area, postcanine surface, incisor surface, and four viscerocranial measures were examined separately for males and females. Our results indicate a marked lack of morphological integration between P-sets within the orofacial subregion and a similar lack of correspondence between jaw size and tooth size. Allometric analyses indicate that mandibular length scales negatively allometric to maxilloalveolar length and to bigonial width, that canine base area scales positively to upper and lower jaw length, and that all the other teeth scale negatively to jaw length. The postcanine surface area was found to be negatively allometric to the canine base area, which in turn scaled isometrically to incisor surface. Hence, any lengthening of the mandible will tend to be associated with a relative shortening of the maxilla, with relatively larger canines and a relative reduction of the cheek teeth.     

金丝猴牙齿与体重间的相关性研究

对金丝猴牙齿与体重间关系的研究结果表明,在雄性中,无论是线性还是面积与颅长之间的相关关系均较雌性的更为紧密。而且,随着体重的增加,雄性牙齿的近中远中长(M/D)也比雌性的增长较快。在上、下颌中,上颌牙齿与颅长的关系表现出更强的相联性。与其他灵长类相比较,金丝猴在取食和咀嚼过程中主要利用颊齿;大的个体具有大的犬齿及一定比例的臼齿面积和齿弓(牙合)面面积;上齿弓(牙合)面面积大于下齿弓(牙合)面面积。也就是说上齿弓提供了比下齿弓更大的咀嚼面积。金丝猴牙齿与体重间的关系位于猴类和人猿类之间,更接近于大猩猩(Gorilla)、疣猴(Colobus)和猕猴。     

The scaling of tongue projection in the veiled chameleon,Chamaeleo calyptratus

Within a year of hatching, chameleons can grow by up to two orders of magnitude in body mass. Rapid growth of the feeding mechanism means that bones, muscles, and movements change as chameleons grow while needing to maintain function. A previous morphological study showed that the musculoskeletal components of the feeding apparatus grow with negative allometry relative to snout–vent length (SVL) in chameleons. Here, we investigate the scaling of prey capture kinematics and muscle physiological cross-sectional area in the veiled chameleon, Chamaeleo calyptratus. The chameleons used in this study varied in size from approximately 3 to 18 cm SVL (1–200 g). Feeding sequences of 12 chameleons of different sizes were filmed and the timing of movements and the displacements and velocities of the jaws, tongue, and the hyolingual apparatus were quantified. Our results show that most muscle cross-sectional areas as well as tongue and hyoid mass scaled with isometry relative to mandible length, yet with negative allometry relative to SVL. Durations of movement also scaled with negative allometry relative to SVL and mandible length. Distances and angles generally scaled as predicted under geometric similarity (slopes of 1 and 0, respectively), while velocities generally scaled with slopes greater than 0 relative to SVL and mandible length. These data indicate that the velocity of jaw and tongue movements is generally greater in adults compared to juveniles. The discrepancy between the scaling of cross-sectional areas versus movements suggests changes in the energy storage and release mechanisms implicated in tongue projection.     

Static intraspecific allometry of the dentition in Otoletnur crassicaudatus

Adult static intraspecific allometry of tooth size was evaluated in a sample of 66 Otolemur crassicaudatus (34 male, 32 female). Tooth areas were calculated from mesiodistal and buccolingual measurements of canines and postcanine teeth of both arcades and were scaled to four viscerocranial measurements: bimaxillary width; maxillo-alveolar length; mandibular length and bigonial width. Individual tooth crown areas were also scaled to total skull length, body length and body weight. From the log-transformed analyses it is concluded that postcanine tooth size was unrelated to body length or weight, and poorly correlated to skull length or jaw size. Although viscerocranial size appears to be independent of body size, these measures are well correlated to skull length. It is shown that the longer the skull, the shorter and narrower the maxilla, and the longer and broader the mandible. Canines are shown to scale negatively allometric to skull length, hence, large animals will have relatively small canines.     

Molar scaling in strepsirrhine primates

We examined how maxillary molar dimensions change with body and skull size estimates among 54 species of living and subfossil strepsirrhine primates. Strepsirrhine maxillary molar areas tend to scale with negative allometry, or possibly isometry, relative to body mass. This observation supports several previous scaling analyses showing that primate molar areas scale at or slightly below geometric similarity relative to body mass. Strepsirrhine molar areas do not change relative to body mass(0.75), as predicted by the metabolic scaling hypothesis. Relative to basicranial length, maxillary molar areas tend to scale with positive allometry. Previous claims that primate molar areas scale with positive allometry relative to body mass appear to rest on the incorrect assumption that skull dimensions scale isometrically with body mass. We identified specific factors that help us to better understand these observed scaling patterns. Lorisiform and lemuriform maxillary molar scaling patterns did not differ significantly, suggesting that the two infraorders had little independent influence on strepsirrhine scaling patterns. Contrary to many previous studies of primate dental allometry, we found little evidence for significant differences in molar area scaling patterns among frugivorous, folivorous, and insectivorous groups. We were able to distinguish folivorous species from frugivorous and insectivorous taxa by comparing M1 lengths and widths. Folivores tend to have a mesiodistally elongated M1 for a given buccolingual M1 width when compared to the other two dietary groups. It has recently been shown that brain mass has a strong influence on primate dental eruption rates. We extended this comparison to relative maxillary molar sizes, but found that brain mass appears to have little influence on the size of strepsirrhine molars. Alternatively, we observed a strong correlation between the relative size of the facial skull and relative molar areas among strepsirrhines. We hypothesize that this association may be underlain by a partial sharing of the patterning of development between molar and facial skull elements.     

Relationships between the size and spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton, and jaw biomechanics

The relationship between human craniofacial morphology and the biomechanical efficiency of bite force generation in widely varying muscular and skeletal types is unknown. To address this problem, we selected 22 subjects with different facial morphologies and used magnetic resonance imaging, cephalometric radiography, and data from dental casts to reconstruct their craniofacial tissues in three dimensions. Conventional cephalometric analyses were carried out, and the cross-sectional sizes of the masseter and medial pterygoid muscles were measured from reconstituted sections. The potential abilities of the muscles to generate bite forces at the molar teeth and mandibular condyles were calculated according to static equilibrium theory using muscle, first molar, and condylar moment arms. On average, the masseter muscle was about 66% larger in cross section than the medial pterygoid and was inclined more anteriorly relative to the functional occlusal plane. There was a significant positive correlation (P less than 0.01) between the cross-sectional areas of the masseter and medial pterygoid muscles (r = 0.75) and between the bizygomatic arch width and masseter cross-sectional area (r = 0.56) and medial pterygoid cross-sectional area (r = 0.69). The masseter muscle was always a more efficient producer of vertically oriented bite force than the medial pterygoid. Putative bite force from the medial pterygoid muscle alone correlated positively with mandibular length and inversely with upper face height. When muscle and tooth moment arms were considered together, a system efficient at producing force on the first molar was statistically associated with a face having a large intergonial width, small intercondylar width, narrow dental arch, forward maxilla, and forward mandible. There was no significant correlation between muscle cross-sectional areas and their respective putative bite forces. This suggests that there is no simple relationship between the tension-generating capacity of the muscles and their mechanical efficiency as described by their spatial arrangement. The study shows that in a modern human population so many combinations of biomechanically relevant variables are possible that subjects cannot easily be placed into ideal or nonideal categories for producing molar force. Our findings also confirm the impression that similar bite-force efficiencies can be found in subjects with disparate facial features.     

Static intraspecific allometry of jaws and teeth in Cercopithecus aethiops

Adult static intraspecific allometry of jaw size and tooth area was evaluated in a sample of 100 Cercopithecus aethiops crania (50 male, 50 female). Tooth areas were calculated from mesiodistal and buccolingual measurements of all the teeth in both arcades and were scaled to four viscero-cranial measurements: bimaxillary breadth, maxillo-alveolar length, mandibular length and bigonial width. Allometric coefficients calculated for jaw dimensions alone indicate tighter viscerocranial integration in females than in males. A finding of note was that half of the variation in maxillo-alveolar length may be accounted for by variation in mandibular length: females are isometric, males negatively allometric.
A similar degree of allometric mosaicism was found when maxillary incisor size was scaled to maxillary length and width. In females, the relationship was negatively allometric, whilst incisor size in males was found to be unrelated to either. Negative allometry characterized the relationship of canine base area to jaw length in both sexes, with males additionally being positively allometric to mandibular width.
The scaling of postcanine tooth areas to jaw length was characterized by a dichotomous pattern: males showed significant mandibular integration whilst females showed only significant maxillary integration. Compensatory tooth size interaction between maxillary canine base area and the summed incisor and postcanine areas was suggested by the significant negative allometric relation between them.     

Scaling of lumbar vertebrae in anthropoids and implications for evolution of the hominoid axial skeleton

We investigated allometric relationships between vertebral centrum cranial surface areas and body weight and skeletal lumbar length in extant platyrrhine and cercopithecid species. Platyrrhines have smaller lumbar vertebral centra regarding the cranial surface area relative to their body weight than extant catarrhines. However, the stress to the spine of quadrupeds is not only influenced by the body weight but also its length, which contributes to the amount of bending moment. Our results indicated that platyrrhines and cercopithecids have similar lumbar vertebral centrum surface areas when they are scaled on the product of the body weight and skeletal lumbar length. Platyrrhines generally tend to have relatively short lumbar columns for a given body weight. As a result of this tendency, their vertebral centra appear relatively small if only body weight is taken into account. The centrum surface area is rather constant relative to the product of the body weight and skeletal lumbar length within platyrrhines or cercopithecids, despite the fact that skeletal lumbar length is in itself rather variable relative to body weight. This result indicates that the vertebral centrum articular area, the lumbar column length and the body weight are strongly correlated with each other and that such relationships are similar between platyrrhines and cercopithecids. These relationships were observed using both the zygapophyseal and rib definitions of the lumbar vertebrae. However, they were more clearly observed when the zygapophyseal definition was adopted. It appeared that lumbar vertebrae of Proconsul nyanzae (KNM−MW 13142) had distinctively smaller surface areas relative to its body weight and lumbar length than for platyrrhines and cercopithecids, differing from extant hominoids, which have comparatively larger lumbar vertebrae. In the case of Morotopithecus, the lumbar vertebral surface area seems to be as large as in extant platyrrhines and cercopithecids if it had a reduced number of lumbar vertebrae. It is uncertain whether its lumbar vertebral surface area was as large as in extant hominoids. Electronic Publication     

A biomechanical analysis of mandibular scaling in old world monkeys

Scaling of mandibular dimensions in male Old World monkeys was investigated. Mandibular condyle length, width, and area were regressed separately against body mass and mandibular length for a total of 14 species of Cercopithecoids. Scaling of mandibular depth and width against both body mass and mandibular length were also investigated. When results of regression analysis using the two different independent variables (body mass and mandibular length) were compared, there were significant pattern differences in scaling of cercopithecines versus colobines. Compared to body mass, male cercopithecines had relatively large mandibles (length, width, and depth) and also relatively large condyles (length, width, and area). However, compared to mandibular length, cercopithecines had relatively transversely thin and shallow mandibles and relatively narrow condyles. It is shown that a “biomechanical” interpretation of mandibular scaling patterns against body mass in Old World monkeys demonstrates only that cercopithecines have prognathic faces, an already well-known and well-documented condition. When the biomechanical effects of prognathic faces are controlled for (by scaling against mandibular length), it is shown that cercopithecines possess special adaptations in condyle length while colobines possess special adaptations in condyle width and mandibular depth and width. These results clearly demonstrate the importance of selecting a relevant reference variable in scaling studies where biomechanical interpretations are attempted.     

Ontogenetic scaling of the morphology and biomechanics of the feeding apparatus in the Pacific hagfish Eptatretus stoutii

The form and function of the support skeleton, musculature and teeth were examined in an ontogenetic series of Pacific hagfish Eptatretus stoutii spanning about a six-fold range in total length (L(T)). Tooth area, feeding apparatus length, basal plate size, theoretical dental plate retractile force, penetration force and applied tooth stress were measured relative to body size. Morphological variables (e.g. tooth area and basal plate size) scaled with positive allometry and functional variables (e.g. retractile force and applied tooth stress) scaled isometrically with L(T). These results suggest that juveniles do not undergo ontogenetic dietary changes and consume functionally equivalent prey to adults, although adults can grasp proportionally larger portions of food. Low tooth stress in juveniles and adults imposes mechanical constraints to puncturing and tearing, which are circumvented by a preference for softer prey tissue or the inclusion of knotting behaviours for reducing tougher prey.     

Variation in dental occlusion and arches among Melanesians of Bougainville Island, Papua New Guinea. II. Clinical variation, geographic microdifferentiation and synthesis

Patterns of geographic microdifferentiation for dental occlusion and the size and shape of the dental arches are described for 14 villages on Bougainville Island, Papua New Guinea. Occlusal variables, such as overjet, overbite, molar relationships, crowding or spacing, and malalignment vary less among villages than do arch length and width. Arch length and width decrease in size from north to south. The pattern of biological distance among villages for occlusal variables and arch size correspond poorly to anthropometric, linguistic, geographic and migrational distances. The value of occlusal variables and arch size for discriminating among populations, the biological interpretation of multivariate data and the objectives of research on geographic microdifferentiation are discussed.     

Is the Clavicle of Apes Long? An Investigation of Clavicular Length in Relation to Body Mass and Upper Thoracic Width

An elongated clavicle is one of the distinct features of apes and humans. It plays an important role in providing mobility as well as stability for the shoulder joints. The relative length of the clavicle is an especially important factor in limiting the range of shoulder joint excursion. It is said that among primates, Asian apes, i.e., gibbons and orang-utans, have very long clavicles. At the same time, they also have a wide upper thoracic cage, which may diminish the effective length of the clavicle. To clarify the length of the clavicle in apes, from the standpoint of the functional anatomy of the shoulder girdle, we examined clavicular length in 15 anthropoid species exhibiting various positional behaviors. The results confirm that clavicle length in Asian apes is long, and chimpanzees have a short clavicle like that of Old and New World monkeys, when scaled to body mass. The clavicular length of chimpanzees, however, is intermediate between Old World monkeys and Asian apes when scaled against thoracic width. Therefore, living apes can be grouped together, albeit just barely, by possession of a relatively long clavicle for their thoracic cage size. Interestingly, New World monkeys tend to exhibit a longer clavicle than Old World monkeys of equivalent body mass or thoracic cage width. Although it is unclear whether the ancestral condition of clavicular length in anthropoids was similar to that of living Old or New World monkeys, an elongation of clavicle was an important step toward evolution of the modern body plan of hominoids.     

Congenital defects of the upper lateral incisors: Multivariate analysis of measurements of the other teeth,the superior arch,head and face

The survey of a French male population allowed us to ascertain 75 propositi with one or two missing ULI, 59 propositi with one or two reduced ULI and 99 controls on whom measurements (mesiodistal and buccolingual diameters) of all teeth of the superior arch are available. Principal Component Analysis gave a first estimated principal component highly correlated with each of the dental measurements or arch measurements. This size factor was eliminated by observing the plane of the second and third principal components. Strikingly different clusters of MD diameters or BL diameters were observed for the controls, the propositi missing one or two of the ULI and the propositi with reduced ULI. For the controls, the arch length is correlated with the MD molar diameters and the MD incisor diameter, the arch width being isolated from the other measurements. For the propositi with missing ULI, among the dental measurements the MD and BL diameters cluster, the arch length is isolated as are the arch widths. For the propositi with reduced ULI, the arch length is closer to the dental measurements while the widths, especially the first one, are isolated. The best discriminant measurements are the diameters of the first premolars and the canine, the first arch width and the arch length. Among controls, the arch is narrowed and shorter for the propositi with absence and wider for the propositi with reduction. Teeth measurements are always smaller in propositi.     

Jaw morphology and function in living and fossil old world monkeys

This allometric investigation on a sample of 29 cercopithecine and 22 colobine taxa augments the data and implications of prior work on subfamilial variation in mandibular form and function in recent Cercopithecidae. To increase the size range encompassed by living cercopithecines and colobines, I included many of the larger-bodied fossil specimens. These analyses serve to fill a gap in our understanding of size-related changes in masticatory function and symphyseal morphology and curvature in extant and extinct Old World monkeys. Results of subfamilial scaling comparisons indicate that for a given jaw length, colobines possess significantly more robust corpora and symphyses than those of cercopithecines, especially at smaller sizes. Following from previous work, the most plausible explanation for why the subfamilies differ in relative corporeal and symphyseal dimensions is that colobine mandibles experience elevated loads and greater repetitive loading during mastication due, on average, to processing a diet of tough leaves and/or seeds. Although colobines have relatively larger symphyses, subfamilial analyses of symphyseal curvature demonstrate that they evince less symphyseal curvature vis-à-vis cercopithecines of a common size. Moreover, both subfamilies exhibit similar allometric changes in the degree of curvature, such that larger-bodied Old World monkeys have more curved symphyses than those of smaller taxa. Subfamilial scaling analyses also indicate that colobines possess a shorter M2 bite-point length relative to masseter lever-arm length, but not versus temporalis lever-arm length. Thus, as compared to cercopithecines, colobines can recruit less masseter-muscle force to produce similar bite forces during mastication. In both clades, M² bite-point length scales with positive allometry relative to masseter lever-arm length, such that larger species are less efficient at generating molar bite forces. This seems especially important due to the lack of subfamily difference in M² bite-point:temporalis lever-arm scaling (which is isometric across cercopithecids). A consideration of extinct cercopithecids indicates that many of the large-bodied papionins have more robust corpora, due perhaps to a diet which was of similar toughness to that of extant and extinct colobines. However, the biomechanical arrangements of the masseter and temporalis in all but one fossil cercopithecine and all of the fossil colobine specimens are much as predicted for a subfamilial member of its skull size. That most large-bodied papionins with tougher diets nonetheless maintain a less efficient jaw-muscle configuration may be due to stronger offsetting selection for increased relative canine size and gape.     

Size and shape of the mandibular condyle in primates

The relationships between the size of the articular surface of the mandibular condyle and masticatory muscle size, tooth size, diet, and biomechanical variables associated with mastication were studied by taking 12 measurements on skulls of 253 adult female anthropoid primates, including three to ten specimens from each of 32 species. In regressions of condylar length, width, or area against body weight, logarithmic transformations substantially improve the fit of the equations compared with untransformed data. There is a strong relationship between condylar measurements and body weight, with all correlations being .94 or higher. The slopes of the allometric regressions of length, width, and area of the condylar head indicate slight positive allometry with body size. Folivorous primates have smaller condyles than frugivorous primates, and colobines have smaller condyles than cebids, cercopithecines, or hominoids. When colobines are eliminated, the differences between frugivores and folivores are not significant. However, the two species with the relatively largest condyles are Pongo pygmaeus and Cercocebus torquatus, suggesting that there may be a relationship between unusually large condylar dimensions and the ability to crack hard nuts between the teeth. Cranial features having strong positive correlations with condylar dimensions include facial prognathism, maxillary incisor size, maxillary postcanine area, mandibular ramus breadth, and temporal fossa area. These data are interpreted as indicating that relatively large condyles are associated with relatively large masticatory muscles, relatively inefficient mandibular biomechanics, and a large dentition. These relationships support the growing evidence that the temporomandibular joint is a stress-bearing joint in normal function.     

Metrical dental analysis on golden monkey (Rhinopithecus roxellana)

Dental variation in the Chinese golden monkey (Rhinopithecus roxellana) is here evaluated by univariate, bivariate, and multivariate analyses. Allometric analyses indicate that canines and P3s are positively, but other dimensions negatively scaled to mandible and maxilla, and to body size. With the exception of the mesiodistal dimensions of I₁ and M₃, and the buccolingual dimension of P₄, mandibular dental variables show similar scaling relative to body size. Analysis of residuals shows that males have significantly larger canine, P³ and buccolingual dimensions of the postcanine teeth (M² and M³) than females. A significant difference in shape between the sexes is found in the buccolingual dimension of the upper teeth, but not in the mandible. Unlike the situation in some other species, female golden monkeys do not exhibit relatively larger postcanine teeth than males. In fact, the reverse is true, expecially for M²s and M³s. The fact that most of the dental variables show low negative allometry to body size might be related a cold environment that has led to the development of larger body size with reduced energy loss. When the raw data are examined by Discriminant Function Analysis the sexes are clearly distinguishable.     

Ontogeny,function, and scaling of the mandibular symphysis in papionin primates

In vivo study of mastication in adult cercopithecine primates demonstrates a link between mandibular symphyseal form and resistance to “wishboning,” or lateral transverse bending. Mechanical consideration of wishboning at the symphysis indicates exponentially higher stresses along the lingual surface with increasing symphyseal curvature. Lengthening the anteroposterior width of the symphysis acts to resist these higher loads. Interspecific adult cercopithecine allometries show that both symphyseal curvature and symphyseal width exhibit positive allometry relative to body mass. The experimental and allometric data support an hypothesis that the cercopithecine mandibular symphysis is designed to maintain functional equivalence—in this case dynamic strain similarity—in wishboning stress and strain magnitudes across adult cercopithecines. We test the hypothesis that functional equivalence during masticatory wishboning is maintained throughout ontogeny by calculating relative stress estimates from morphometric dimensions of the mandibular symphysis in two cercopithecine primates, Macaca fascicularis and M. nemestrina. Results indicate no significant differences in relative stress estimates among the two macaque ontogenies and an interspecific sample of adult papionin primates. Further, relative stress estimates do not change significantly throughout ontogeny in either species. These results offer the first evidence for the maintenance of functional equivalence in stress and strain levels during postnatal growth in a habitually loaded cranial structure. Scaling analyses demonstrate significant slope differences for both symphyseal curvature and width between the ontogenetic and interspecific samples. The distinct interspecific cercopithecine slopes are realized by a series of ontogenetic transpositions in both symphyseal curvature and width. Throughout papionin ontogeny, symphyseal curvature increases with less negative allometry, while symphysis width increases with less positive allometry versus the interspecific pattern. As symphyseal curvature and width are inversely proportional to one another in estimating relative stresses, functionally equivalent stress levels are maintained both ontogenetically and interspecifically, because the relatively slower rate of allometric increase in symphyseal curvature during growth is compensated for by a slower rate of allometric increase in symphyseal width. These results indicate the primacy of maintaining functional equivalence during growth and the need for ontogenetic data in understanding the evolutionary processes that affect form–function relations as well as the interspecific patterning of adult form across a clade. J. Morphol. 235:157–175, 1998. © 1998 Wiley-Liss, Inc.     

Understanding reproductive allometry in turtles: A slippery “slope”

Measures of reproductive output in turtles are generally positively correlated with female body size. However, a full understanding of reproductive allometry in turtles requires logarithmic transformation of reproductive and body size variables prior to regression analyses. This allows for slope comparisons with expected linear or cubic relationships for linear to linear and linear to volumetric variables, respectively. We compiled scaling data using this approach from published and unpublished turtle studies (46 populations of 25 species from eight families) to quantify patterns among taxa. Our results suggest that for log–log comparisons of clutch size, egg width, egg mass, clutch mass, and pelvic aperture width to shell length, all scale hypoallometrically despite theoretical predictions of isometry. Clutch size generally scaled at ~1.7 to 2.0 (compared to an isometric expectation of 3.0), egg width at ~0.5 (compared to an expectation of 1.0), egg mass at ~1.1 to 1.3 (3.0), clutch mass at ~2.5 to 2.8 (3.0), and pelvic aperture width at 0.8–0.9 (1.0). We also found preliminary evidence that scaling may differ across years and clutches even in the same population, as well as across populations of the same species. Future investigators should aspire to collect data on all these reproductive parameters and to report log–log allometric analyses to test our preliminary conclusions regarding reproductive allometry in turtles.     

The relationship between facial proportions and root length in the dentition of dogs

The present analysis represents a follow-up to a previous experimental study in which facial shortening obtained in rats by septum removal produced also shortening of the molar roots. In the present study relative root length was compared in short-faced as against long-faced dogs and significant correlations between relative facial length and dental root length were found. Root shortening in the maxilla of short-faced dogs clusters around the areas of the premaxillary-maxillary suture and the maxillary-palatine suture. For the mandible it shifts one tooth more distally and is of lower statistical significance. This distribution seems to tie in with the greater growth arrest in the above sutural areas in the maxilla of short-faced dogs and the lesser growth arrest of their mandible.     

Platyrrhine incisors and diet

Despite the relatively large size of anthropoid incisors in relation to the remainder of the dental arcade, and their prominent role in the preprocessing of food prior to ingestion, comparatively little is known about the functional morphology of anthropoid incisor shape and crown curvature. The relationship between incisor allometry and diet is well documented for both platyrrhines and catarrhines; however, similar relationships between incisor shape and crown curvature have to date only been reported for living and fossil members of the superfamily Hominoidea. Given the limited taxonomic diversity among the extant members of that group, it is difficult to firmly establish the relative influence of phylogeny and dietary function in the governance of incisor crown curvature. Unlike hominoids, which are represented by only five living genera, extant platyrrhines are a more varied group that includes 16 ecologically diverse genera. In an effort to clarify the functional relationship between maxillary and mandibular incisor crown curvature and diet, this study uses high resolution polynomial curve fitting to quantify mesiodistal and cervicoincisal curvature for a taxonomically diverse platyrrhine sample (n = 133 individuals representing 18 taxa) with well documented dietary behavior. Results were consistent with prior analyses of hominoid incisor curvature and identify a significant and positive correlation between incisor crown curvature and diet such that increasing curvature is associated with a proportionate increase in frugivory. These results are independent confirmation of the results reported from a previous analysis of hominoid incisor curvature and provide new evidence to suggest that diet is the primary governing factor influencing anthropoid incisor curvature.