Brain expansion and comparative prenatal ontogeny of the non-hominoid primate cranial base

Jeffery, Nathan

doi:10.1016/j.jhevol.2003.08.002

Cited by 51 publications

(60 citation statements)

References 54 publications

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“…The age variable EGA was computed from biparietal diameter and is therefore susceptible to added variances such as head shrinkage and deformation. However, this and previous studies Spoor, 2002, 2004;Jeffery, 2003) have shown that the informative and comparative value of this computed age variable far outweighs any possible deleterious effects of the added noise. Head position is another possible source of unaccounted variance since it may have directly affected laryngeal position and thereby indirectly influenced pharyngeal dimensions in a number of specimens.…”

Section: Discussionsupporting

confidence: 41%

“…Although the value of the coefficient is low, it remained statistically significant while controlling for background growth-related variances. These findings may explain the continued discrepancy between adult interspecific data that point to increases in relative brain size as the major influence on cranial base angulation and fetal data that do not [compare Ross and Ravosa (1993), Spoor (1997), and Ross et al (2004) to Jeffery and Spoor (2002) and Jeffery (2003)]. It is plausible that the fetal data reflect a different mechanism of basicranial angulation (i.e., retroflexion due to oropharyngeal enlargement) that may also be present across genera but is masked by the more prevailing influence of brain expansion (Jeffery, 2003).…”

Section: Table 2 Landmarks and Measurementsmentioning

confidence: 97%

“…The major benefits include that hrMRI is noninvasive and can demonstrate soft as well as hard tissues, albeit indirectly by contrast against softer tissues (i.e., greater water or fat content). Details of the imaging gradients, probes, and pulse sequence employed are also given in detail elsewhere (Jeffery, 1999(Jeffery, , 2002(Jeffery, , 2003Jeffery and Spoor, 2002). For each specimen, the hrMRI acquisition matrix was maintained at 256 ϫ 256.…”

Section: Sample and Imagingmentioning

confidence: 99%

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Cranial base angulation and growth of the human fetal pharynx

Jeffery

2005

Anat. Rec.

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The upper airway controls the mechanisms of breathing, swallowing, and vocalization. Information on its normal ontogenetic associations is therefore crucial for understanding human speech evolution as well as the developmental etiology of speech abnormalities. Of particular interest to evolutionary morphologists is the proposed structural association between the upper airway and the cranial base. The present study aims to elucidate whether cranial base angulation is linked to growth of the upper airway during human fetal life. Forty postmortem human fetuses ranging from 10 to 29 weeks of gestation were imaged with high-resolution magnetic resonance imaging. Measurements of basicranial angle, hyoid depth, hormion height, and pharyngeal area were taken from sagittal images. Results show a significant correlation between the internal and external basicranial angles but the correlation between relative hyoid depth and internal cranial base angle was not significant. Findings show a significant correlation between increases in the size of the oropharynx relative to the nasopharynx and increases in the internal cranial base angle (retroflexion). These findings give limited support (r rank ϭ 0.46; P Ͻ 0.01) for the hypothesis that restructuring of the upper airway underlies basicranial retroflexion during prenatal life.

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Section: Discussionsupporting

confidence: 41%

Section: Table 2 Landmarks and Measurementsmentioning

confidence: 97%

Section: Sample and Imagingmentioning

confidence: 99%

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Cranial base angulation and growth of the human fetal pharynx

Jeffery

2005

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“…Note that Alouatta seniculus, an arboreal quadrupedal taxon that can maintain more orthograde body postures during bouts of locomotion (i.e., climbing, walking, and bridging) (Fleagle and Mittermeier, 1980;Youlatos, 1993Youlatos, , 1998, exhibits a very large angle value and often groups with Lemur catta and Varecia variegata, both dedicated terrestrial/arboreal quadrupeds (Rowe, 1996;Fleagle, 1999). Such a value indicates pronograde head and neck postures (Strait and Ross, 1999), probably related to this species' enlarged hyolaryngeal complex (Biegert 1963;Jeffery, 2003). …”

mentioning

confidence: 99%

Functional morphology of the primate head and neck

Nalley

Grider-Potter

2015

American J Phys Anthropol

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The vertebral column plays a key role in maintaining posture, locomotion, and transmitting loads between body components. Cervical vertebrae act as a bridge between the torso and head and play a crucial role in the maintenance of head position and the visual field.Despite its importance in positional behaviors, the functional morphology of the cervical region remains poorly understood, particularly in comparison to the thoracic and lumbar sections of the spinal column. This study tests whether morphological variation in the primate cervical vertebrae correlates with differences in postural behavior. Phylogenetic generalized least-squares analyses were performed on a taxonomically broad sample of 26 extant primate taxa to test the link between vertebral morphology and posture. Kinematic data on primate head and neck postures were used instead of behavioral categories, in an effort to provide a more direct analysis of our functional hypothesis. Results provide evidence for a function-form link between cervical vertebral shape and postural behaviors. Specifically, taxa with more pronograde heads and necks and less kyphotic orbits exhibit cervical vertebrae with longer spinous processes, indicating increased mechanical advantage for deep nuchal musculature, and craniocaudally longer vertebral bodies and more coronally oriented zygapophyseal articular facets, suggesting an emphasis on curve formation and maintenance within the cervical lordosis, coupled with a greater resistance to translation and ventral displacement. These results not only document support for functional relationships in cervical vertebrae features across a wide range of primate taxa, but highlight the utility of quantitative behavioral data in functional investigations. ! !Despite the critical role of the vertebral column in postural and locomotor behaviors, our understanding of primate cervical vertebral form and function is markedly limited compared to knowledge of thoracolumbar functional morphology (Schultz, 1942(Schultz, , 1961Toerien, 1961;Mercer, 1999;Manfreda et al., 2006; Ankel-Simons, 2007;Mitteroecker et al., 2007). Many early descriptions of primate cervical morphology as a whole concluded that skeletal variation was limited and that the region was thus relatively uninformative regarding functional or phylogenetic questions (e.g., Toerien, 1961; Ankel 1967 Ankel , 1970 Ankel , 1972. Notable exceptions include Slijper (1946) and Schultz (1961). Slijper's 1946 work investigated the presacral vertebral column across animals and developed several body-axis models stilled used today (e.g., Clauser, 1980;Shapiro, 1991;Dunbar et al., 2008;Stevens, 2013). Furthermore, the author recognized the positive relationship between body size and spinous process size and argued that the differences in cervical spinous process length between humans, great apes, and monkeys was related to head posture and position maintenance (see Toerien (1961) as well). Schultz (1961) focused mostly on measurements of the thoracic and lumbar regions, but descr...

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“…• Jeffery 33 , in a comparative study of intrauterine skull base growth in nonhuman primates, questions the spatial-packing hypothesis.…”

Section: Mccarthymentioning

confidence: 99%