Primate cranial diversity

Abstract

Many studies in primate and human evolution focus on aspects of cranial morphology to address issues of systematics, phylogeny, and functional anatomy. However, broad analyses of cranial diversity within Primates as an Order are notably absent. In this study, we present a 3D geometric morphometric analysis of primate cranial morphology, providing a multivariate comparison of the major patterns of cranial shape change during primate evolution and quantitative assessments of cranial diversity among different clades. We digitized a set of 18 landmarks designed to capture overall cranial shape on male and female crania representing 66 genera of living primates. The landmark data were aligned using a Generalized Procrustes Analysis and then subjected to a principal components analysis to identify the major axes of cranial variation. Cranial diversity among clades was compared using multivariate measurements of variance. The first principal component axis reflects differences in cranial flexion, orbit size and orientation, and relative neurocranial volume. In general, it separates strepsirrhines from anthropoids. The second axis reflects differences in relative cranial height and snout length and primarily describes differences among anthropoids. Eulemur, Mandrillus, Pongo, and Homo are among the extremes in cranial shape. Anthropoids, catarrhines, and haplorhines show a higher variance than prosimians or strepsirrhines. Hominoids show the highest variance in cranial shape among extant primate clades, and much of this diversity is driven by the unique cranium of Homo sapiens.

Old World Monkeys

“…Scientists currently recognise 20 different living genera divided into two distinct adaptive radiations: the cercopithecines, who live in terrestrial and arboreal habitats and forage for a variety of foods, but mostly fruit; and the colobines, who live in arboreal habitats and rely upon leaves and seeds for major portions of their diet. Interestingly, cercopithecoids have achieved this diversity in spite of being less varied anatomically and in their social behaviour than other primate groups (Szalay and Delson, 1979;Di Fiore and Rendall, 1994; but see Fleagle et al, 2010). Cercopithecoids also have an extensive fossil record, especially in Africa, which shows that Old World monkeys are both a relatively recent adaptive radiation and that in the past they were even more diverse and occupied an even greater geographic, taxonomic and ecological range (Jablonski, 2002;Jablonski and Frost, 2010).…”

Evolução morfológica no crânio de Lemuriformes (Primates:Strepsirrhini)

“…These methods are based in simulating a large set of random selection vectors in order to measure a Matrix ability to respond. The Malagasy primates display an impressive range of sizes, specially considering the recently extinct forms (Bennett and Goswami, 2012;Fleagle et al, 2010;Godfrey and Jungers, 2003;Mittermeier et al, 2010). Given that our results suggest natural selection as an evolutionary process contributing to the divergence between 5 means, we can estimate selection gradients and evaluate species magnitudes of response to selection and its alignment with the adaptive landscape.…”

“…O primeiro trabalho a investigar a morfologia craniana em um contexto mais amplo da diversidade da ordem Primates foi Fleagle et al (2010 pecialmente no gênero Eulemur). Além disso, existem trabalhos que reportam dimorfismo de grau leve a moderado (quando comparado com aquele presente em demais primatas) em medidas relacionadas a tamanho corpóreo e de dentição, como caninos e premolares.…”

“…Com o intuito de ampliar as análises e resultados apresentados por Fleagle et al (2010) levando em consideração a diversidade morfólógica apresentada no registro fóssil, Bennett and Goswami (2012) utilizaram uma metodologia semelhante seguida por análise discriminante em um conjunto de 33 mar- …”

“…15 The relative brain size is usually adopted as a measure of encephalization and has been hypothesized as the main factor influencing the evolution of the cranial base angle among primates (Lieberman et al, 2008;Moss and Young, 1960). Although, Strepsirrhini primates show the lowest levels of encephalization among primates, while being notorious for their relative large eyes and a long rostrum (Bennett and Goswami, 2012;Fleagle et al, 2010;Isler et al, 2008).…”