Patterns and magnitudes of craniofacial covariation in extant cercopithecids

Abstract

The cranium contains almost all of the vertebrate sensory organs and plays an essential role in vertebrate evolution. Research on the primate cranium has revealed that it is both highly integrated and modular, but studies have historically focused on covariance between the neurocranium and facial skeleton rather than on bones specific to special senses such as vision. The goal of this work is to investigate patterns and magnitudes of craniofacial covariation in extant cercopithecids with particular attention to the orbits. This study takes a quantitative approach using data collected from 38 homologous cranial landmarks across 11 genera of cercopithecid monkeys (Cercopithecidae, N = 291). These data demonstrate that both patterns and magnitudes of craniofacial covariation differ across Cercopithecidae at subfamily, tribe, and genus levels, with the strongest integration in the papionins (and specifically Papio) and significantly weaker covariation in the colobines, particularly Presbytis. Orbital height does not covary with other measurements of the cranium to the same degree as other cranial traits in Cercopithecidae and is highly constrained across the family. This study has important implications for our understanding of the evolution and development of morphological diversity in the cercopithecid cranium and evolution of the primate eye. This study also highlights the potential error of broad assumptions about generalizing patterns and magnitudes of modularity and integration across primates. Additionally, these findings reiterate the importance of trait selection for interpreting fossil taxonomy, as craniofacial covariation may impact phenotypes commonly used to differentiate fossil primate species.

A Pleistocene assemblage of near‐modern Papio hamadryas from the Middle Awash study area, Afar Rift, Ethiopia

“…All cranial data were collected by TAM from the Chai Baro fossils following standard protocols (see Monson, 2020; Monson et al, 2017). The 10 measurements collected include facial length, interorbital breadth, maximum width at the upper canines, muzzle width at ectomolare , muzzle width at the maxillary fossae, nasal height, nasal width, palatal length, palatal width at the third molars, and palatal width at the upper canines.…”

Keeping 21st Century Paleontology Grounded: Quantitative Genetic Analyses and Ancestral State Reconstruction Re-Emphasize the Essentiality of Fossils

“…The ANOVA also revealed a distinct separation of three of the papionin genera: Papio , Theropithecus , and Mandrillus . These three genera are derived among the cercopithecids in having elongated muzzles, which is well-known to demonstrate positive allometry [ 114 , 115 , 116 , 117 ]. Looking more closely, we see that Papio and Theropithecus differ from the other genera in all six dental traits.…”

Phylogenetic evolutionary aspects of the vertebrate skull - an approach for teaching: vertebrate skull

“…An important and interesting aspect about the human evolution starts from the modification of the jaw muscles that became weaker due to a putative mutation and allowed the growth of the hominids' encephalon (NODEN;TRAINOR, 2005). From this data, hypothetically, in association with the fact that this muscle, the masseter, originates from the supraorbital ridge in primates and australopithecines, and this origin is in the temporal of hominids, has allowed the growth of the frontal bone and the development of the part of the brain associated with language, the fine motor coordination, the abstraction, the higher cognitive functions, the frontal lobe (MADDIN et al, 2020;MONSON, 2020).…”

“…Due to the many data on the bones, mainly the skull, two situations can occur: the excess of information that should be the scope of the specialists, or an oversimplification that will fail in the teaching processes with the danger of generating errors of interpretation (HIDELBRAND; GOSLOW, 2006;MONSON, 2020).…”

“…MATA; MATA; AVERSI-FERREIRA, 2010; KOYABU; MAIER; SÁNCHEZ-VILLAGRA, 2012).In primates, the dermal bones of the upper-anterior portion of the skull have become enormous to house an encephalon of immense proportions compared to other animals(PEREIRA-DE-PAULA, 2010;MONSON, 2020;ABREU et al, 2021). The periotic bone fuses with the squamous bone to form a temporal bone, and the tympanic membrane is a new structure(NODEN;TRAINOR, 2005;MONSON, 2020). The basosphenoid and presphenoid bones lie anterior to the occipital bone and a new element, the mesoethmoid bone appears in the nasal portion and fuses with the orbitoesphenoid and aliesphenoid bones.…”