The pattern of thickness arrangement is established early in ontogeny but CVT increases and changes in distribution until adolescence. Several factors may influence CVT, such as the brain, muscles, vessels, and sutures.

Background/Aim: Computed Tomography (CT) is a powerful tool in craniofacial research that focuses on morphological variation. In this field, an ontogenetic approach has been taken to study the developmental sources of variation and to understand the basis of morphological evolution. This work aimed to determine measurement error (ME) in cranial CT in diverse developmental stages and to characterize how this error relates to different types of landmarks.

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In humans, the frontal sinus (FS) is located in the medial part of the supraorbital region, sometimes expanded throughout the frontal squama. It exhibits high morphological variability, but its general form appears to be constrained by surrounding structures. The goal of this study is to analyze FS growth and test for covariation between FS volume and the glabellar region, upper nasal region, bone thickness and endocranial size in a human sample from Argentina. The sample comprises 149 reconstructions derived from computed tomography images of individuals aged 0–31 years. Volume of the FS and measurements of the surrounding structures were recorded. The FS growth trajectory was assessed by parametric and nonparametric methods, and covariation was determined using correlations and partial correlations. The FS volume could be measured at an age of about 6 years and older; adults had no aplasia but hyperplasia was found in some cases. Since the most conspicuous characteristic found was variation among individuals, the nonparametric smoothing spline produced very poor fitting. The modified logistic function was the only parametric method providing significant parameters. Sexes differed in the age at which FS growth began and ended, with FS developing earlier but at a slower rate in females than in males. The FS volume did not correlate with either upper nasal width or endocranial volume, but it correlated with bone thickness measurements (mainly from the glabellar region), even when age was held constant. Expansion of the FS at the frontal poles also correlated with frontal bone thickness. Despite the difficulty in modeling and predicting the trajectory and morphology of FS, our results suggest that it is affected by its surrounding bony environment.

Most studies on craniofacial morphology have focused on adult individuals, but patterns of variation are the outcome of genetic and epigenetic variables that interact throughout ontogeny. Among cranial regions, the orbits exhibit morphological variation and occupy an intermediate position between neurocranial and facial structures. The main objective of this work was to analyze postnatal ontogenetic variation and covariation in the morphology of the orbital region in a cross-sectional series of humans from 0 to 31 years old. Landmarks and semilandmarks were digitized on the orbital rim, as well as in neighboring neural and facial structures. Data were analyzed using geometric morphometrics. Results indicated that orbital size increases during the first years of postnatal life, while the shape of the orbital aperture does not change significantly with age. In general, the pattern and magnitude of shape covariation do not vary markedly during postnatal life although some subtle shifts were documented. Additionally, the shape of the orbital aperture is more related to the anterior neurocranium than to zygomatic structures, even when the allometry is adjusted. Although we expected some influence from postnatal craniofacial growth and from some functional factors, such as mastication, on the development of the orbits, this assumption was not completely supported by our results. As a whole, our findings are in line with the prediction of an early influence of the eyes and extraocular tissues on orbital morphology, and could be interpreted in relation to processes promoting early neural development that coordinately affects orbital traits and the neurocranial skeleton. Anat Rec,

The skull is considered a modular structure in which different parts are influenced by different factors and, as a result, achieve adult shape at different ages. Previous studies have suggested that the basicranium presents a modular pattern that distinguishes sagittal and lateral parts, probably affected by the brain and masticatory structures, respectively. The vault of modern humans, in contrast, has been considered as a highly integrated system mainly influenced by brain growth. Here, we explored developmental shape variation in sagittal and lateral ectocranial vault in humans in order to assess if both regions are ontogenetically dissociated. We used a sample of 135 cranial computed tomography images from 0 to 31 ages. Landmarks and semilandmarks were collected on sagittal and lateral regions and geometric morphometric techniques were applied separately for each region. On the shape coordinates, we used Goodall's Ftest in order to assess the age when the adult configuration is attained. Principal component analysis enabled us to evaluate shape variation during ontogeny. Results indicated that both sagittal and lateral structures attain adult shape at early adolescence. Both regions express coordinated shape modifications probably due to shared developmental factors. It is concluded that masticatory muscles may not exert a strong enough influence to produce independent variation in the lateral traits. Thus, it is likely that the brain integrates sagittal and lateral parts of the vault across human ontogeny.

The neurocranium of hominid species has been largely studied with reference to the midsagittal plane, with variations being attributed to brain evolution. By contrast, there is limited information on variation in non-midsagittal regions, which are the points of insertion of muscles and bony structures related to mastication. This work aims to analyze ontogenetic changes and sexual dimorphism (SD) in midsagittal and non-midsagittal neurocranial structures from a contemporary human sample comprising 138 computed tomography (CT) cranial images of individuals ranging from infants to adults. Morphology of the vault and the base was assessed by registering landmarks and semilandmarks, which were analyzed by geometric morphometrics, and the endocranial volume (EV). The results of regressions and Kruskal-Wallis test indicate that the major size and shape changes in both midsagittal and non-midsagittal regions occur during infancy and juvenility; shape changes are also associated with an increase in EV. The size of the midsagittal vault, the shape of the non-midsagittal vault and the size of the base show an extension of ontogenetic trajectories. Sexes show similar changes in shape but different changes in size. We conclude that brain growth appears to be an important factor influencing the morphology of the neurocranium, at least during infancy and childhood. Subsequent changes may be attributed to osteogenic activity and the differential growth of the brain lobes. Masticatory-related bony structures and muscles may not be strong enough factors to induce independent modifications in non-midsagittal structures. The small influence of the cranial muscles would explain why the human neurocranium is a quite integrated structure.

RESUMEN Diversos estudios proponen que el neurocráneo en Homo sapiens es una estructura integrada y que la morfología de la bóveda y la base se asocia con modificaciones del cerebro. En este estudio se evaluó la covariación ontogénica en el endocráneo PALABRAS CLAVE chimpancé; tomografía computada; integración; cerebro tegrados y se producen hasta etapas tardías de la ontogenia: elongación de la bóveda y la base, distanciamiento entre el foramen magnun y la placa cribiforme, retroflexión del ángulo basicraneano y descenso de los polos temporales. A partir del análisis PLS se observó que los cambios en la base y la bóve-da covarían, pero cuando se ajustó el efecto alométrico, dicha covariación se hizo no significativa, tal como ocurre en Homo sapiens. Esto sugiere que el aumento ontogénico del volumen endocraneano -en relación con el crecimiento cerebral-constituye un factor común de integración entre la bóveda y la base en ambas especies. Sin embargo, es probable que en el chimpancé se sume la influencia de distintas estructuras faciales que promuevan variación y covariación en el endocráneo. Rev Arg Antrop Biol 16(2):79-91, 2014.KEY WORDS chimpanzee; computed tomography; integration; brain ABSTRACT Several studies propose that the neurocranium in Homo sapiens is an integrated structure, being the growing brain the factor that influences the vault and the base morphology. The goal of this study is to assess endocranial ontogenetic covariation in Pan troglodytes, another encephalized primate. Fifty-two 3D reconstructions derived from computed tomographies of adult and subadult specimens were analyzed. After segmentation of the endocranial volumes, twenty-seven landmarks were registered. Through their configuration, Centroid size and Procrustes coordinates were obtained, and Principal Components Analysis, regression, correlation, ANOVA and Goodall's F-test were performed in order to evaluate size and shape changes against age and allometries. The results indicated that significant