Fiorenza L., Bruner E. 2017. Cranial shape variation in adult howler monkeys (Alouatta seniculus). Am. J. Primatol. [link]
Recently, Evin et al. 2016 have published a study comparing the accuracy of the three-dimensional reconstruction of five wolf crania using both photogrammetry and high-resolution surface scanner. For the photogrammetric images acquisition, they used an 8-megapixel (DSLR) Canon EOS 30D camera, mounted with a Canon EF 24–105mmf/4 L IS USMlens. The scanner-based 3D models were created using a Breuckmann StereoScan structured light scanner (http://www.breuckmann.com). The resulting 3D models were compared first through visual observation, and second with the computation of a mesh-to-mesh deviation map. The pairs of models were spatially aligned (using a least-square optimisation best-fit criterion), followed by a 3D landmark-based geometric morphometric approach using corresponding analyses. The results show that photogrammetric 3D models are as accurate in terms of coloration, texture, and geometry, as the highest-end surface scanners. Minimal differences between photogrammetric 3D models and surface scanner-based models have been only identified on intricate topological regions, such the tooth row. Photogrammetry is becoming a common tool in archaeological and anthropological research. The major advantage of this technique is the speed and ease of image acquisition and reconstruction. Photogrammetry is an equally good alternative and less expensive than other more common techniques, such as structured light or surface scanners. In terms of archaeological samples conservation, photogrammetry could be in the future an excellent alternative to provide accurate replica models that can be widely accessible for research, without affecting the original collections.
Gizéh Rangel de Lázaro
Emeritus Professor Colin Groves was an internationally-recognized and respected taxonomist in Mammalogy and Primatology. After completing his PhD dissertation at University College London in 1966 on Gorilla skull variation and taxonomy, Colin was appointed as lecturer at the Australian National University (ANU). Colin was an integral part of the ANU Biological Anthropology Department, welcoming discussions with internationally recognized researchers and undergraduate students alike, always made himself available and believed in an “open-door” policy for teaching. For me, he was an inspirational and influential mentor, teacher, colleague and friend who was an irreplaceable part of the Australian and International Primatology and Anthropology community. An online condolence book has been organised for those wishing to pay their respects.
In a recent paper, Fabbri et al analyzed the relationship between brain and cranial vault shape in the transition from reptiles to birds. To assess the evolution of this relationship they used a broad sample including Aves, Lepidosauria, Crocodylia, Archosauria, and Reptilia. To assess developmental differences they included an ontogenetic sample of Alligator mississipiensis and Gallus gallus. The results showed that the relationship between the vault bones and the brain is conserved across these taxa, with the frontal bone positioned over the forebrain and the parietal bone over the midbrain or over midbrain and posterior forebrain. Nonetheless, they observed some shape variations, namely on the relative sizes of the frontal and parietal bones and in the position of the fronto-parietal suture relative to the forebrain-midbrain boundary. These two structures are significantly correlated, with the fronto-parietal suture being either anterior to (e.g. stem reptiles) or nearly aligned with (e.g. crown birds) the forebrain-midbrain boundary. In terms of ontogeny, chickens have a shorter ontogenetic trajectory than alligators, as the brain and skull of embryos are similar to the adult ones. The brain and skull of alligators develop with negative allometry, with the brain relatively large in early stages but becoming relatively small during growth. Conversely, the skull and brain of chicken grow with positive allometry, and the authors suggest the brain should be considered peramorphic in Aves. Overall the results stress the important role of the brain in shaping the cranial vault. The authors wonder whether the intimate relationship between brain and frontal and parietal bones is the key for the conservation of the cranial vault across vertebrates.
The Scalable Brain Atlas (SBA) is a fully web-based display engine for brain atlases, imaging data and ontologies. It allows client websites to show brain region related data in a 3D interactive context and provides services to look up regions, generate thumbnails or download nomenclature – and delineation data … [Atlas] [3Dviewer]
Educational medical resources provided by IMAIOS include interactive atlases and tools. The human e-Anatomy atlas combines digital imaging and computational tools for all anatomical regions from the human brain , with 3D reconstruction and labeling of neuroanatomical features, extending to the human pelvic girdle with 3D reconstructions of bones and arteries. Subscription to these utilities is useful for healthcare professionals but is focused on educational institutions and lecturers with access available for students enrolled in courses. For educational purposes, the resource includes quiz templates for each anatomical region and a virtual environment with enjoyable but educational tools for human lower limb anatomy using the Ninja Lower Limb game. The inclusion of resources for Veterinary Medicine with the vet-Anatomy atlas in similar design as the Human e-Anatomy atlas. All these tools are accessible through computer access and common mobile and tablet platforms in multiple languages.
We have published one more paper on the morphology of the precuneus, this time featuring a sample of non-human primates, in collaboration with James Rilling and Todd Preuss from the Emory University (Atlanta, USA). Modern humans have a much larger precuneus than chimpanzees both in absolute and relative size. Taking into account the large brain size in our species, we investigated the midsagittal morphology in non-human primates as to test whether precuneus proportions are influenced by allometric factors. We did a geometric morphometric analysis on a total of 42 MRIs from the National chimpanzee brain resource database, including 5 species of apes and 4 species of monkeys. A first analysis, conducted on the species averages, showed that the main pattern of midsagittal variation involves the general shape of the braincase, which might be due to cranial constraints rather than to changes in proportions of specific brain regions. This main shape pattern separates monkeys from apes, as the former display flatter, elongated brains (with capuchins being the flattest), while the latter exhibit rounder brains with frontal bulging (especially orangutans). This morphological variation correlates with brain size, except for gorillas (which brain is large but elongated), and gibbons (which have smaller but round brains). A second analysis was conducted only on chimpanzees and macaques, to compare two species with different brain size. In neither case the proportions of the precuneus displayed major differences between species or size-related changes. However, as in humans, precuneus size is very variable within each species, suggesting a remarkable plasticity. Overall, the results suggest that precuneus expansion in modern humans is a species-specific characteristic of our species, rather than a simple consequence of increase in brain size. Further studies should address the histological and functional processes involved in this morphological change.
We have just published a new study on the spatial relationship between visual and endocranial structures in adult modern humans, chimpanzees, and fossil humans. The survey was conducted in collaboration with Michael Masters from Montana Tech (USA), who previously hypothesized that, in modern humans, the positioning of the orbits below the frontal lobes coupled with a reduced face could result in spatial conflict among ocular, cerebral, and craniofacial structures. This could lead to vision problems, such as myopia. In addition, another study evidenced that eye and orbit dimensions have a stronger correlation with the frontal lobes, rather than with the occipital lobes, indicating that the ocular structures can be more constrained by spatial (physical) than by functional (vision) relationships. In this study we used geometric morphometrics to investigate the longitudinal (antero-posterior) spatial relationships between orbito-ocular and endocranial structures. First, we addressed the the position of the eye relatively to the frontal and temporal cortex, on a sample of 63 modern humans’ MRIs. Second, we addressed the spatial relationship between orbital and endocranial structures on a CT sample comprising 30 modern humans, 3 chimpanzees, and 3 fossil humans (Bodo, Broken Hill 1, Gibraltar 1).
The results of the MRI analysis show that in adult modern humans the main pattern of shape variation deals with the antero-posterior position of the eye relative to the temporal lobes. Individuals which eyes are closer to the temporal lobes exhibit rounder frontal outline and antero-posterior shorter eyes, indicating a possible physical constraint associated with the spatial contiguity between the eye and the middle cranial fossa. A second pattern describes the supero-inferior position of the eye, relatively to the frontal lobe. Also in this case, proximity is apparently associated with slight changes in eye form. Individuals with larger volumes of the frontal and temporal lobes tend to have eyes located more posteriorly, closer to the temporal lobe, although with no apparent change in the shape of the eye. These results partially support Master’s hypothesis, suggesting reciprocal spatial patterns influencing brain and eye form.
When analyzing orbits and braincase through CT data, the main intra-specific variation among modern humans concerns the orientation of the orbit, not the position. Nonetheless, analyzing humans, apes, and fossil hominids all together, the main differences deal with the distance between orbits and braincase: they are separated in chimps, overlapped in modern humans, and in intermediate position in fossils. In this case, fossils belong to the hypodigm of Homo heidelbergensis. Modern humans are characterized by larger temporal lobes when compared with other living primates, and longer middle cranial fossa. The proximity with the eyeballs due to face reduction can stress further a morphogenetic spatial conflict between orbits and brain. Next step: 3D analyses, ontogenetic series, and vision impairment.
Since brain does not fossilize, brain endocast (i.e., replica of the inner surface of the braincase, Figure 1) constitutes the only direct evidence for reconstructing hominin brain evolution (Holloway, 1978; Holloway et al., 2004a). In this context, paleoneurology has suffered from strong limitations due to the fragmentary nature of the fossil record and the absence of any information regarding subcortical elements in extinct taxa. Additionally, variation in brain shape and organization (and in the corresponding endocast) is technically difficult to capture, as stated by Bruner (2017a, p. 64): “[…] the smooth and blurred geometry of the brain, its complex and complicated mechanisms, and its noticeable individual variability make any research associated with its morphology very entangled and difficult to develop within fixed methodological approaches.” An emblematic example might be the reluctance of paleoneurologists to consider the sulcal imprints visible on the endocranial surface because of the substantial uncertainties in describing such features in fossil specimens and related debates (e.g., the lunate sulcus in the Taung child’s endocast; Falk, 1980a, 2009, 2014; Holloway, 1981a; Holloway et al., 2004b). In 1987, Tobias even came to the conclusion that “The recognition of specific cerebral gyri and sulci from their impressions on an endocast is a taxing, often subjective and even invidious undertaking which arouses much argumentation” (p. 748) …