The ontogeny of sexual dimorphism in the cranium of Bornean orang-utans (Pongo pygmaeus pygmaeus) as detected by principal-components analysis

Masterson, Thomas J; Leutenegger, Walter

doi:10.1007/bf02197055

Cited by 21 publications

(13 citation statements)

References 43 publications

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“…Among the taxa investigated in this study, males show a higher frequency of sagittal cresting than do females. These results are consistent with patterns of cranial growth beyond dental maturity and with spheno‐occipital fusion being delayed in gorillas and orangutans (Randall, ; Röhrer‐Ertl, ; Leutenegger & Masterson, ,b; Masterson & Leutenegger, , ; Uchida, ; Hens, , ; Balolia et al. ; Gordon et al.…”

Section: Discussionsupporting

confidence: 81%

“…Other evidence of a secondary growth spurt in Po. pygmaeus comes from the facial skeleton and the cranium (Röhrer‐Ertl, ; Leutenegger & Masterson, ,b; Masterson & Leutenegger, , ; Uchida, ; Hens, , ; Balolia et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…Finally, an understanding of the biological basis of sagittal crest development related to the timing of other indicators of maturity (e.g. Shea, , ; Röhrer‐Ertl, ; Leutenegger & Masterson, ,b; Masterson & Leutenegger, , ; Uchida, ; Hens, , ; Balolia et al. ; Gordon et al.…”

Section: Discussionmentioning

confidence: 99%

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Sagittal crest formation in great apes and gibbons

2017

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The frequency of sagittal crest expression and patterns of sagittal crest growth and development have been documented in hominoids, including some extinct hominin taxa, and the more frequent expression of the sagittal crest in males has been traditionally linked with the need for larger-bodied individuals to have enough attachment area for the temporalis muscle. In the present study, we investigate sagittal cresting in a dentally mature sample of four hominoid taxa (Pan troglodytes schweinfurthii, Gorilla gorilla gorilla, Pongo pygmaeus pygmaeus and Hylobates lar). We investigate whether sagittal crest size increases with age beyond dental maturity in males and females of G. g. gorilla and Po. pyg. pygmaeus, and whether these taxa show sex differences in the timing of sagittal crest development. We evaluate the hypothesis that the larger sagittal crest of males may not be solely due to the requirement for a larger surface area than the un-crested cranial vault can provide for the attachment of the temporalis muscle, and present data on sex differences in temporalis muscle attachment area and sagittal crest size relative to cranial size. Gorilla g. gorilla and Po. pyg. pygmaeus males show significant relationships between tooth wear rank and sagittal crest size, and they show sagittal crest size differences between age groups that are not found in females. The sagittal crest emerges in early adulthood in the majority of G. g. gorilla males, whereas the percentage of G. g. gorilla females possessing a sagittal crest increases more gradually. Pongo pyg. pygmaeus males experience a three-fold increase in the number of specimens exhibiting a sagittal crest in mid-adulthood, consistent with a secondary growth spurt. Gorilla g. gorilla and Po. pyg. pygmaeus show significant sex differences in the size of the temporalis muscle attachment area, relative to cranial size, with males of both taxa showing positive allometry not shown in females. Gorilla g. gorilla males also show positive allometry for sagittal crest size relative to cranial size. Our results suggest that although patterns of sagittal crest expression have limited utility for taxonomy and phylogeny reconstruction, they could be useful for reconstructing aspects of social behaviour in some extinct hominin taxa. In particular, our results in G. g. gorilla and Po. pyg. pygmaeus, which suggest that the size of sagittal crests in males cannot be solely explained by the surface area required for attachment of the temporalis muscle, offer partial support for the hypothesis that large sagittal crests form in response to sexual selection and may play a role in social signalling.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

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Sagittal crest formation in great apes and gibbons

2017

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“…Rather than being surprising, this result serves to confirm a growing body of allometric work which indicates the prevalence of ontogenetic scaling in the development of sexual dimorphism among higher primates including Pongo pygmaeus (Leutenegger & Masterson, 1989a, 1989bMasterson & Leutenegger, 1990), both Pan and Gorilla (Shea, 1985a(Shea, , 1985b(Shea, , 1986, and several cercopithecoid taxa (Freedman, 1962;Swindler et al, 1968;Cochard, 1985;Cheverud & Richtsmeier, 1986;Leigh & Cheverud, 1991 ;Ravosa 1991 ;German et al, 1994). Furthermore, the evidence supports the hypothesis that two processes, rate and time hypermorphosis, are the means by which sexual dimorphism develops among Liberian chimpanzees.…”

Section: Discussionsupporting

confidence: 57%

Heterochrony and sexual dimorphism in the skull of the Liberian chimpanzee (Pan troglodytes verus)

Anemone

Swindler

1999

Int. J. Anthropol.

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Heterochrony and Sexual Dimorphism in the Skull of the Liberian Chimpanzee (Pan troglodytes verus)AIIometric methods and theory derived from principles of relative growth provide new and powerful approaches to an understanding of the nature and development of sexual d imorphism among living primates. The Frankfurt collection of Liberian chimpanzee skulls and mandibles provides a large skeletal sample from a single natural population of wild shot animals, including individuals of all ages and both sexes, and allows investigation of allometric and heterochronic patterns of sexual dimorphism. Univariate, bivariate, and multivariate analyses are utilized in this study in order to ascertain the ontogenetie nature of male-female differences in the skull of the Liberian chimpanzee. The results of univariate and multivariate analyses indicate that, while overall levels of sexual dimorphism in the chimpanzee skull are small, the greatest differences are in dimensions of the viscerocranium, while neurocranial dimensions and orbital size tend to be less dimorphic. Bivariate regressions of 21 cranial variables against basicranial length document positive allometry in many iacial and mandibular dimensions, and isometry or negative allometry for most neurocranial dimensions. The data confirm previous work in chimpanzees and other anthropoid primates suggesling that males and females are "ontogenetically scaled" in most cranial traits.That is, males and females share the same cranial growth trajectories, although ending up at different points. Both rate and time hypermorphosis are suggested as underlying causes of ontogenetie scaling in the Liberian chimpanzee.

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“…Such developmental variation is likely to influence the expression of sexual dimorphism in the skeleton by varying the relative duration of growth among skeletal components. Studies of craniofacial development generally point to patterns of ontogenetic scaling between males and females, i.e., male growth curves tend to be extensions of the female growth curves (Leutenegger and Masterson, 1989a,b;Richtsmeier and Cheverud, 1989;Masterson and Leutenegger, 1990;Ravosa, 1991;Corner and Richtsmeier, 1991Ravosa and Ross, 1994). Heterogeneity in the rate and duration of growth among different skeletal regions accounts for different patterns of dimorphism.…”

Section: "Reverse Dimorphism"mentioning

confidence: 99%

Sexual dimorphism in primate evolution

Plavcan

2001

Am. J. Phys. Anthropol.

164

175

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Sexual dimorphism is a pervasive phenomenon among anthropoid primates. Comparative analyses over the past 30 years have greatly expanded our understanding of both variation in the expression of dimorphism among primates, and the underlying causes of sexual dimorphism. Dimorphism in body mass and canine tooth size is familiar, as is pelage and "sex skin" dimorphism. More recent analyses are documenting subtle differences in the pattern of skeletal dimorphism among primates. Comparative analyses have corroborated the sexual selection hypotheses, and have provided a more detailed understanding of the relationship between sexual selection, natural selection, and mating systems in primates. A clearer picture is emerging of the relative contribution of various selective and nonselective mechanisms in the evolution and expression of dimorphism. Most importantly, recent studies have shown that dimorphism is the product of changes in both male and female traits. Developmental studies demonstrate the variety of ontogenetic pathways that can lead to dimorphism, and provide additional insight into the selective mechanisms that influence dimorphism throughout the lifetime of an animal. Evidence from the fossil record suggests that dimorphism probably evolved in parallel twice, and the dimorphism in some extinct hominoids probably exceeded that of any living primate. Our advances in understanding the behavioral/ecological correlates of dimorphism in living primates have not improved our ability to reconstruct social systems in extinct species on the basis of dimorphism alone, beyond the inference of polygyny or intense male-male competition. However, our understanding of the behavioral/ecological correlates of growth and development, and of the expression of dimorphism as a function of separate changes in male and female traits, offers great potential for inferring evolutionary changes in behavior over time

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The ontogeny of sexual dimorphism in the cranium of Bornean orang-utans (Pongo pygmaeus pygmaeus) as detected by principal-components analysis

Cited by 21 publications

References 43 publications

Sagittal crest formation in great apes and gibbons

Sagittal crest formation in great apes and gibbons

Heterochrony and sexual dimorphism in the skull of the Liberian chimpanzee (Pan troglodytes verus)

Sexual dimorphism in primate evolution

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