Christoph P. E. Zollikofer | University of Zurich, Switzerland (original) (raw)
Papers by Christoph P. E. Zollikofer
As one of the essential components of the fossil record, shells of molluscs provide crucial data ... more As one of the essential components of the fossil record, shells of molluscs provide crucial data for taxonomic, phylogenetic or evolutionary studies. The mollusc shell has often very few discrete morphological characters, and its most important character is its three-dimensional (3-D) geometry, which is well diversified, continuous and highly inte-grated. However, standard morphometric methods remain mostly two-dimensional (2-D) and do not account for the ontogenetic changes of the shell, which are preserved thanks to its accretionary mode of growth. This study proposes a new non-destructive method enabling acquisition of three-dimensional quantitative morphometric parame-ters that thoroughly describe the geometry of coiled mollusc shells throughout their ontogeny. First, digital three-dimensional data of a shell is acquired by means of micro-computed tomography, which produces a series of grey-scaled, two-dimensional images. Second, all these stacked images are processed to obtain ...
The Plio-Pleistocene site of Dmanisi (Georgia) has yielded an exceptionally well-preserved and mo... more The Plio-Pleistocene site of Dmanisi (Georgia) has yielded an exceptionally well-preserved and morphologically diverse sample of cranial and postcranial remains of early Homo within a rich archeological and faunal context. This unique ensemble offers new comparative perspectives on the origin and dispersal of our own genus in Africa and Asia. Here we ask how patterns of morphological diversity within the Dmanisi paleopopulation, and between Dmanisi and African/Asian H. erectus, are related to processes of hominin phylogeography. Variation in size and shape within the Dmanisi sample is considerable and, like in modern human populations, a large proportion of it can be related to variation in basic developmental processes. This perspective has several implications for the interpretation of H.erectus sensu lato: (1)at its lower (Plio-Pleistocene) boundary, separation from early Homo (cf. habilis)becomes increasingly difficult; (2) during the Pleistocene, links between Dmanisi and East ...
Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on mod... more Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on modern data acquisition and imaging technologies such as micro-computed or synchrotron tomography and interactive visualization. The acquired high-resolution volume data sets have sizes in the order of tens to hundreds of GBs, and typically exhibit spatially complex internal structures. Such large structural volume data sets represent a grand challenge to be explored, analyzed and interpreted by means of interactive visualization, since the amount of data to be rendered is typically far beyond the current performance limits of interactive graphics systems. As a new approach to tackle this bottleneck problem, we employ higher-order tensor approximations (TAs). We demonstrate the power of TA to represent, and focus on, structural features in volume data. We show that TA yields a high data reduction at competitive rate distortion and that, at the same time, it provides a natural means for mult...
Summary Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fo... more Summary Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Formicidae: Hymenoptera) were recorded during outward and homeward trips to and from a food source. While returning homewards, the animals were supplied with food items of defined mass (load ratio from 1.3 to 6.4) and volume. Under the influence of load, the temporal interleg coordination pattern was maintained (alternating tripod gait), but the spatial tripod pattern was modified. Tripod deformation was found to be proportional to the displacement of the centre of mass induced by the load. Stride length and stride frequency were not altered at any speed when animals carried loads compared with trips without a load. However, in order to maintain stability, mean stride length, mean speed and mean stride frequency were reduced while carrying loads.
Journal of Experimental Biology, 1995
This study examines the effects of body size variation on the optical properties of the compound ... more This study examines the effects of body size variation on the optical properties of the compound eyes of visually guided desert ants belonging to the genus Cataglyphis. Although linear head size may vary by a factor of 2 within conspecific workers and most optical parameters change accordingly, the extent of the visual field remains constant. Comparative measurements carried out on workers of three species (C. albicans, C. bicolor and C. fortis) and on reproductive females and males of one species (C. bicolor) show that the form (size and shape) of the visual field is highly characteristic for each caste/species. A constant visual field is realised by reciprocal scaling rules for the number of ommatidia and the angular spacing of ommatidia. While larger ants have more ommatidia per compound eye, interommatidial angles are reduced accordingly, thus giving rise to a constant visual field. Among conspecific ant workers, the relationship between spatial visual acuity and eye size is sim...
Scientific reports, Jan 26, 2018
The present study attempted to reconstruct 3D brain shape of Neanderthals and early Homo sapiens ... more The present study attempted to reconstruct 3D brain shape of Neanderthals and early Homo sapiens based on computational neuroanatomy. We found that early Homo sapiens had relatively larger cerebellar hemispheres but a smaller occipital region in the cerebrum than Neanderthals long before the time that Neanderthals disappeared. Further, using behavioural and structural imaging data of living humans, the abilities such as cognitive flexibility, attention, the language processing, episodic and working memory capacity were positively correlated with size-adjusted cerebellar volume. As the cerebellar hemispheres are structured as a large array of uniform neural modules, a larger cerebellum may possess a larger capacity for cognitive information processing. Such a neuroanatomical difference in the cerebellum may have caused important differences in cognitive and social abilities between the two species and might have contributed to the replacement of Neanderthals by early Homo sapiens.
Scientific reports, Jan 31, 2018
Inferring the morphology of the last common ancestor of humans, chimpanzees and gorillas is a mat... more Inferring the morphology of the last common ancestor of humans, chimpanzees and gorillas is a matter of ongoing debate. Recent findings and reassessment of fossil hominins leads to the hypothesis that the last common ancestor was not extant African ape-like. However, an African great-ape-like ancestor with knuckle walking features still remains plausible and the most parsimonious scenario. Here we address this question via an evolutionary developmental approach, comparing taxon-specific patterns of shape change of the femoral diaphysis from birth to adulthood in great apes, humans, and macaques. While chimpanzees and gorillas exhibit similar locomotor behaviors, our data provide evidence for distinct ontogenetic trajectories, indicating independent evolutionary histories of femoral ontogeny. Our data further indicate that anthropoid primates share a basic pattern of femoral diaphyseal ontogeny that reflects shared developmental constraints. Humans escaped from these constraints via ...
International Journal of Osteoarchaeology, 2014
Paleopathological cases of skeletal dysplasias (SD) are particularly interesting from a biologica... more Paleopathological cases of skeletal dysplasias (SD) are particularly interesting from a biological as well as biocultural perspective. Evidence of SD is relevant when discussing the antiquity of specific mutations, as well as the social perception of disease in the past. Here we propose a differential diagnosis for a Neolithic case of SD and discuss the possible social correlates of the observed condition. The subject of this study, a child with an age at death of about 12 years from the Late Neolithic site of Schweizersbild (Northern Switzerland), presents a bilateral shortening of the forearm and lower leg, with no further modifications affecting the cranial and postcranial skeleton. Morphological, metric, as well as radiographic analyses point to a diagnosis of Léri Weill dyschondrosteosis (LWD), making the present case the earliest known paleopathological example of this condition. From a biocultural perspective, the skeletal changes affecting the child, together with her/his relatively advanced age, suggest active support from the community, providing new data to inform the debate on the cultural dimensions of disease in prehistory.
Anatomical record (Hoboken, N.J. : 2007), Apr 1, 2017
The bony pelvis of primates is a composite structure serving a variety of functions, and exhibiti... more The bony pelvis of primates is a composite structure serving a variety of functions, and exhibiting a complex pattern of modularity and integration. Still little is known, however, about how patterns of modularity and integration arise, and how they change throughout ontogeny. Here we study the ontogeny of modularity and integration in developmental and functional units of the pelvis of our closest living relatives, the chimpanzees. We use methods of biomedical imaging and geometric morphometrics to quantify pelvic shape change from late fetal stages to adulthood, and to track changes in patterns of covariation within and among pelvic regions. Our results show that both developmental and functional units of the pelvis exhibit significant levels of modularity throughout ontogeny. Modularity of developmental units (ilium, ischium, and pubis) decreases with increasing age, whereas modularity of functional units tends to increase. We suggest that the decreasing modularity and increasing...
Journal of Experimental Biology, 1994
Journal of Experimental Biology, 1994
Proceedings of the National Academy of Sciences of the United States of America, Jan 25, 2016
The bony pelvis of adult humans exhibits marked sexual dimorphism, which is traditionally interpr... more The bony pelvis of adult humans exhibits marked sexual dimorphism, which is traditionally interpreted in the framework of the "obstetrical dilemma" hypothesis: Giving birth to large-brained/large-bodied babies requires a wide pelvis, whereas efficient bipedal locomotion requires a narrow pelvis. This hypothesis has been challenged recently on biomechanical, metabolic, and biocultural grounds, so that it remains unclear which factors are responsible for sex-specific differences in adult pelvic morphology. Here we address this issue from a developmental perspective. We use methods of biomedical imaging and geometric morphometrics to analyze changes in pelvic morphology from late fetal stages to adulthood in a known-age/known-sex forensic/clinical sample. Results show that, until puberty, female and male pelves exhibit only moderate sexual dimorphism and follow largely similar developmental trajectories. With the onset of puberty, however, the female trajectory diverges subst...
International Journal of Oral and Maxillofacial Surgery, 1998
The purpose of this study was to assess the importance of stereolithographic models (SLMs) for pr... more The purpose of this study was to assess the importance of stereolithographic models (SLMs) for preoperative diagnosis and planning in craniofacial surgery and to examine whether these models offer valuable additional information as compared to normal CT scans and 3D CT images. Craniofacial SLMs of 20 patients with craniomaxillofacial pathology were made. A helical volume CT scan of the anatomic area involved delivered the necessary data for their construction. These were built with an SLA 250 stereolithography apparatus (3D-Systems, Valencia, CA, USA), steered by FORM-IT/DCS software (University of Zurich, Switzerland). The stereolithography models were classified according to pathology, type of surgery and their relevance for surgical planning. Though not objectively measurable, it was beyond doubt that relevant additional information for the surgeon was obtained in cases of hypertelorism, severe asymmetries of the neuro- and viscerocranium, complex cranial synostoses and large skull defects. The value of these models as realistic "duplicates" of complex or rare dysmorphic craniofacial pathology for the purpose of creating a didactic collection should also be emphasized. The models proved to be less useful in cases of consolidated fractures of the periorbital and naso-ethmoidal complex, except where there was major dislocation.
Journal of Experimental Biology
Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Fo... more Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Formicidae: Hymenoptera) were recorded during outward and homeward trips to and from a food source. While returning homewards, the animals were supplied with food items of defined mass (load ratio from 1.3 to 6.4) and volume. Under the influence of load, the temporal interleg coordination pattern was maintained (alternating tripod gait), but the spatial tripod pattern was modified. Tripod deformation was found to be proportional to the displacement of the centre of mass induced by the load. Stride length and stride frequency were not altered at any speed when animals carried loads compared with trips without a load. However, in order to maintain stability, mean stride length, mean speed and mean stride frequency were reduced while carrying loads.
Journal of Experimental Biology
The locomotory behaviour of workers of 12 ant species belonging to four different genera (Formici... more The locomotory behaviour of workers of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals walking on smoked-glass plates. Subsequent multivariate analyses of footfall positions and walking kinematics revealed a set of constant features characterizing ant locomotion. The alternating tripod gait prevails over a wide range of speeds. The temporal rigidity of tripod coordination is paralleled by spatially rigid footfall patterns. Tripod geometry is preserved irrespective of speed and curvature. When walking around curves, tripods are rotated relative to the walking trajectory. Whereas stride length on the inner side of the curve is shortened, that on the outer side is independent of curvature.
Journal of Experimental Biology
The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Catagl... more The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals during walking on smoked-glass plates. Subsequent multivariate analyses of walking kinematics and footfall positions showed marked species-specific as well as size-dependent differences in the locomotory behaviour. The geometric properties of the footfall patterns resulting from the alternating tripod gait scale to leg dimensions in a geometric manner. At high speed, footprint distances between succeeding tripods exceed maximum leg extension, indicating that ants are 'trotting' from one tripod to the next one with intermittent aerial phases. In at least one species (Cataglyphis bombycina), there is evidence for quadrupedal locomotion at the highest speed. The functional relationship between stride length (s, the distance between successive footprints of the same foot) and speed (v) was best described by a curvilinear model, s=av b. Exponent b ranges from 0.3 to 0.6 and reveals differences between species. Within species, exponent b is constant, whereas factor a scales to leg length. Females and males show metachronal interleg coordination patterns rather than the alternating tripod coordination pattern seen in workers of the same species.
Fossil molluscs are one of the essential components of the fossil record. They are a crucial sour... more Fossil molluscs are one of the essential components of the fossil record. They are a crucial source of data for biochronozones, palaeoenvironmental reconstructions and macroevolutionary patterns, as well. However, the rather simple morphology of their shell, with very few ...
As one of the essential components of the fossil record, shells of molluscs provide crucial data ... more As one of the essential components of the fossil record, shells of molluscs provide crucial data for taxonomic, phylogenetic or evolutionary studies. The mollusc shell has often very few discrete morphological characters, and its most important character is its three-dimensional (3-D) geometry, which is well diversified, continuous and highly integrated. However, standard morphometric methods remain mostly two-dimensional (2-D) and do not account for the ontogenetic changes of the shell, which are preserved thanks to its accretionary mode of growth. This study proposes a new non-destructive method enabling acquisition of three-dimensional quantitative morphometric parameters that thoroughly describe the geometry of coiled mollusc shells throughout their ontogeny. First, digital three-dimensional data of a shell is acquired by means of microcomputed tomography, which produces a series of grey-scaled, two-dimensional images. Second, all these stacked images are processed to obtain a three-dimensional reconstruction of the shell, from which a centreline is extracted. Finally, the geometry of shell aperture through ontogeny is extracted by successive cross-sectioning of the shell with a succession of planes, each of these being perpendicular to this centreline. The resulting outlines of the successive apertures can be quantified by elliptic Fourier analysis. These geometric parameters, coupled with the displacement vector of the successive cross-sectioning planes, constitute an n-dimensional morphometric space, in which ontogenetic trajectories of different individuals and species can be compared. The approach proposed in this study provides a basis for the quantitative analysis of growth patterns within and across species.
Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on mod... more Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on modern data acquisition and imaging technologies such as micro-computed or synchrotron tomography and interactive visualization. The acquired volume data sets are not only of high-resolution but in particular exhibit complex spatial structures at different levels of scale (e.g. variable spatial expression of multiscale periodic growth structures in tooth enamel). Such highly structured volume data sets represent a tough challenge to be analyzed and explored by means of interactive visualization due to the amount of raw volume data to be processed and filtered for the desired features. As an approach to address this bottleneck by multiscale feature preserving data reduction, we propose higher-order tensor approximations (TAs). We demonstrate the power of TA to represent, and highlight the structural features in volume data. We visually and quantitatively show that TA yields high data reducti...
As one of the essential components of the fossil record, shells of molluscs provide crucial data ... more As one of the essential components of the fossil record, shells of molluscs provide crucial data for taxonomic, phylogenetic or evolutionary studies. The mollusc shell has often very few discrete morphological characters, and its most important character is its three-dimensional (3-D) geometry, which is well diversified, continuous and highly inte-grated. However, standard morphometric methods remain mostly two-dimensional (2-D) and do not account for the ontogenetic changes of the shell, which are preserved thanks to its accretionary mode of growth. This study proposes a new non-destructive method enabling acquisition of three-dimensional quantitative morphometric parame-ters that thoroughly describe the geometry of coiled mollusc shells throughout their ontogeny. First, digital three-dimensional data of a shell is acquired by means of micro-computed tomography, which produces a series of grey-scaled, two-dimensional images. Second, all these stacked images are processed to obtain ...
The Plio-Pleistocene site of Dmanisi (Georgia) has yielded an exceptionally well-preserved and mo... more The Plio-Pleistocene site of Dmanisi (Georgia) has yielded an exceptionally well-preserved and morphologically diverse sample of cranial and postcranial remains of early Homo within a rich archeological and faunal context. This unique ensemble offers new comparative perspectives on the origin and dispersal of our own genus in Africa and Asia. Here we ask how patterns of morphological diversity within the Dmanisi paleopopulation, and between Dmanisi and African/Asian H. erectus, are related to processes of hominin phylogeography. Variation in size and shape within the Dmanisi sample is considerable and, like in modern human populations, a large proportion of it can be related to variation in basic developmental processes. This perspective has several implications for the interpretation of H.erectus sensu lato: (1)at its lower (Plio-Pleistocene) boundary, separation from early Homo (cf. habilis)becomes increasingly difficult; (2) during the Pleistocene, links between Dmanisi and East ...
Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on mod... more Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on modern data acquisition and imaging technologies such as micro-computed or synchrotron tomography and interactive visualization. The acquired high-resolution volume data sets have sizes in the order of tens to hundreds of GBs, and typically exhibit spatially complex internal structures. Such large structural volume data sets represent a grand challenge to be explored, analyzed and interpreted by means of interactive visualization, since the amount of data to be rendered is typically far beyond the current performance limits of interactive graphics systems. As a new approach to tackle this bottleneck problem, we employ higher-order tensor approximations (TAs). We demonstrate the power of TA to represent, and focus on, structural features in volume data. We show that TA yields a high data reduction at competitive rate distortion and that, at the same time, it provides a natural means for mult...
Summary Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fo... more Summary Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Formicidae: Hymenoptera) were recorded during outward and homeward trips to and from a food source. While returning homewards, the animals were supplied with food items of defined mass (load ratio from 1.3 to 6.4) and volume. Under the influence of load, the temporal interleg coordination pattern was maintained (alternating tripod gait), but the spatial tripod pattern was modified. Tripod deformation was found to be proportional to the displacement of the centre of mass induced by the load. Stride length and stride frequency were not altered at any speed when animals carried loads compared with trips without a load. However, in order to maintain stability, mean stride length, mean speed and mean stride frequency were reduced while carrying loads.
Journal of Experimental Biology, 1995
This study examines the effects of body size variation on the optical properties of the compound ... more This study examines the effects of body size variation on the optical properties of the compound eyes of visually guided desert ants belonging to the genus Cataglyphis. Although linear head size may vary by a factor of 2 within conspecific workers and most optical parameters change accordingly, the extent of the visual field remains constant. Comparative measurements carried out on workers of three species (C. albicans, C. bicolor and C. fortis) and on reproductive females and males of one species (C. bicolor) show that the form (size and shape) of the visual field is highly characteristic for each caste/species. A constant visual field is realised by reciprocal scaling rules for the number of ommatidia and the angular spacing of ommatidia. While larger ants have more ommatidia per compound eye, interommatidial angles are reduced accordingly, thus giving rise to a constant visual field. Among conspecific ant workers, the relationship between spatial visual acuity and eye size is sim...
Scientific reports, Jan 26, 2018
The present study attempted to reconstruct 3D brain shape of Neanderthals and early Homo sapiens ... more The present study attempted to reconstruct 3D brain shape of Neanderthals and early Homo sapiens based on computational neuroanatomy. We found that early Homo sapiens had relatively larger cerebellar hemispheres but a smaller occipital region in the cerebrum than Neanderthals long before the time that Neanderthals disappeared. Further, using behavioural and structural imaging data of living humans, the abilities such as cognitive flexibility, attention, the language processing, episodic and working memory capacity were positively correlated with size-adjusted cerebellar volume. As the cerebellar hemispheres are structured as a large array of uniform neural modules, a larger cerebellum may possess a larger capacity for cognitive information processing. Such a neuroanatomical difference in the cerebellum may have caused important differences in cognitive and social abilities between the two species and might have contributed to the replacement of Neanderthals by early Homo sapiens.
Scientific reports, Jan 31, 2018
Inferring the morphology of the last common ancestor of humans, chimpanzees and gorillas is a mat... more Inferring the morphology of the last common ancestor of humans, chimpanzees and gorillas is a matter of ongoing debate. Recent findings and reassessment of fossil hominins leads to the hypothesis that the last common ancestor was not extant African ape-like. However, an African great-ape-like ancestor with knuckle walking features still remains plausible and the most parsimonious scenario. Here we address this question via an evolutionary developmental approach, comparing taxon-specific patterns of shape change of the femoral diaphysis from birth to adulthood in great apes, humans, and macaques. While chimpanzees and gorillas exhibit similar locomotor behaviors, our data provide evidence for distinct ontogenetic trajectories, indicating independent evolutionary histories of femoral ontogeny. Our data further indicate that anthropoid primates share a basic pattern of femoral diaphyseal ontogeny that reflects shared developmental constraints. Humans escaped from these constraints via ...
International Journal of Osteoarchaeology, 2014
Paleopathological cases of skeletal dysplasias (SD) are particularly interesting from a biologica... more Paleopathological cases of skeletal dysplasias (SD) are particularly interesting from a biological as well as biocultural perspective. Evidence of SD is relevant when discussing the antiquity of specific mutations, as well as the social perception of disease in the past. Here we propose a differential diagnosis for a Neolithic case of SD and discuss the possible social correlates of the observed condition. The subject of this study, a child with an age at death of about 12 years from the Late Neolithic site of Schweizersbild (Northern Switzerland), presents a bilateral shortening of the forearm and lower leg, with no further modifications affecting the cranial and postcranial skeleton. Morphological, metric, as well as radiographic analyses point to a diagnosis of Léri Weill dyschondrosteosis (LWD), making the present case the earliest known paleopathological example of this condition. From a biocultural perspective, the skeletal changes affecting the child, together with her/his relatively advanced age, suggest active support from the community, providing new data to inform the debate on the cultural dimensions of disease in prehistory.
Anatomical record (Hoboken, N.J. : 2007), Apr 1, 2017
The bony pelvis of primates is a composite structure serving a variety of functions, and exhibiti... more The bony pelvis of primates is a composite structure serving a variety of functions, and exhibiting a complex pattern of modularity and integration. Still little is known, however, about how patterns of modularity and integration arise, and how they change throughout ontogeny. Here we study the ontogeny of modularity and integration in developmental and functional units of the pelvis of our closest living relatives, the chimpanzees. We use methods of biomedical imaging and geometric morphometrics to quantify pelvic shape change from late fetal stages to adulthood, and to track changes in patterns of covariation within and among pelvic regions. Our results show that both developmental and functional units of the pelvis exhibit significant levels of modularity throughout ontogeny. Modularity of developmental units (ilium, ischium, and pubis) decreases with increasing age, whereas modularity of functional units tends to increase. We suggest that the decreasing modularity and increasing...
Journal of Experimental Biology, 1994
Journal of Experimental Biology, 1994
Proceedings of the National Academy of Sciences of the United States of America, Jan 25, 2016
The bony pelvis of adult humans exhibits marked sexual dimorphism, which is traditionally interpr... more The bony pelvis of adult humans exhibits marked sexual dimorphism, which is traditionally interpreted in the framework of the "obstetrical dilemma" hypothesis: Giving birth to large-brained/large-bodied babies requires a wide pelvis, whereas efficient bipedal locomotion requires a narrow pelvis. This hypothesis has been challenged recently on biomechanical, metabolic, and biocultural grounds, so that it remains unclear which factors are responsible for sex-specific differences in adult pelvic morphology. Here we address this issue from a developmental perspective. We use methods of biomedical imaging and geometric morphometrics to analyze changes in pelvic morphology from late fetal stages to adulthood in a known-age/known-sex forensic/clinical sample. Results show that, until puberty, female and male pelves exhibit only moderate sexual dimorphism and follow largely similar developmental trajectories. With the onset of puberty, however, the female trajectory diverges subst...
International Journal of Oral and Maxillofacial Surgery, 1998
The purpose of this study was to assess the importance of stereolithographic models (SLMs) for pr... more The purpose of this study was to assess the importance of stereolithographic models (SLMs) for preoperative diagnosis and planning in craniofacial surgery and to examine whether these models offer valuable additional information as compared to normal CT scans and 3D CT images. Craniofacial SLMs of 20 patients with craniomaxillofacial pathology were made. A helical volume CT scan of the anatomic area involved delivered the necessary data for their construction. These were built with an SLA 250 stereolithography apparatus (3D-Systems, Valencia, CA, USA), steered by FORM-IT/DCS software (University of Zurich, Switzerland). The stereolithography models were classified according to pathology, type of surgery and their relevance for surgical planning. Though not objectively measurable, it was beyond doubt that relevant additional information for the surgeon was obtained in cases of hypertelorism, severe asymmetries of the neuro- and viscerocranium, complex cranial synostoses and large skull defects. The value of these models as realistic "duplicates" of complex or rare dysmorphic craniofacial pathology for the purpose of creating a didactic collection should also be emphasized. The models proved to be less useful in cases of consolidated fractures of the periorbital and naso-ethmoidal complex, except where there was major dislocation.
Journal of Experimental Biology
Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Fo... more Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Formicidae: Hymenoptera) were recorded during outward and homeward trips to and from a food source. While returning homewards, the animals were supplied with food items of defined mass (load ratio from 1.3 to 6.4) and volume. Under the influence of load, the temporal interleg coordination pattern was maintained (alternating tripod gait), but the spatial tripod pattern was modified. Tripod deformation was found to be proportional to the displacement of the centre of mass induced by the load. Stride length and stride frequency were not altered at any speed when animals carried loads compared with trips without a load. However, in order to maintain stability, mean stride length, mean speed and mean stride frequency were reduced while carrying loads.
Journal of Experimental Biology
The locomotory behaviour of workers of 12 ant species belonging to four different genera (Formici... more The locomotory behaviour of workers of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals walking on smoked-glass plates. Subsequent multivariate analyses of footfall positions and walking kinematics revealed a set of constant features characterizing ant locomotion. The alternating tripod gait prevails over a wide range of speeds. The temporal rigidity of tripod coordination is paralleled by spatially rigid footfall patterns. Tripod geometry is preserved irrespective of speed and curvature. When walking around curves, tripods are rotated relative to the walking trajectory. Whereas stride length on the inner side of the curve is shortened, that on the outer side is independent of curvature.
Journal of Experimental Biology
The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Catagl... more The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals during walking on smoked-glass plates. Subsequent multivariate analyses of walking kinematics and footfall positions showed marked species-specific as well as size-dependent differences in the locomotory behaviour. The geometric properties of the footfall patterns resulting from the alternating tripod gait scale to leg dimensions in a geometric manner. At high speed, footprint distances between succeeding tripods exceed maximum leg extension, indicating that ants are 'trotting' from one tripod to the next one with intermittent aerial phases. In at least one species (Cataglyphis bombycina), there is evidence for quadrupedal locomotion at the highest speed. The functional relationship between stride length (s, the distance between successive footprints of the same foot) and speed (v) was best described by a curvilinear model, s=av b. Exponent b ranges from 0.3 to 0.6 and reveals differences between species. Within species, exponent b is constant, whereas factor a scales to leg length. Females and males show metachronal interleg coordination patterns rather than the alternating tripod coordination pattern seen in workers of the same species.
Fossil molluscs are one of the essential components of the fossil record. They are a crucial sour... more Fossil molluscs are one of the essential components of the fossil record. They are a crucial source of data for biochronozones, palaeoenvironmental reconstructions and macroevolutionary patterns, as well. However, the rather simple morphology of their shell, with very few ...
As one of the essential components of the fossil record, shells of molluscs provide crucial data ... more As one of the essential components of the fossil record, shells of molluscs provide crucial data for taxonomic, phylogenetic or evolutionary studies. The mollusc shell has often very few discrete morphological characters, and its most important character is its three-dimensional (3-D) geometry, which is well diversified, continuous and highly integrated. However, standard morphometric methods remain mostly two-dimensional (2-D) and do not account for the ontogenetic changes of the shell, which are preserved thanks to its accretionary mode of growth. This study proposes a new non-destructive method enabling acquisition of three-dimensional quantitative morphometric parameters that thoroughly describe the geometry of coiled mollusc shells throughout their ontogeny. First, digital three-dimensional data of a shell is acquired by means of microcomputed tomography, which produces a series of grey-scaled, two-dimensional images. Second, all these stacked images are processed to obtain a three-dimensional reconstruction of the shell, from which a centreline is extracted. Finally, the geometry of shell aperture through ontogeny is extracted by successive cross-sectioning of the shell with a succession of planes, each of these being perpendicular to this centreline. The resulting outlines of the successive apertures can be quantified by elliptic Fourier analysis. These geometric parameters, coupled with the displacement vector of the successive cross-sectioning planes, constitute an n-dimensional morphometric space, in which ontogenetic trajectories of different individuals and species can be compared. The approach proposed in this study provides a basis for the quantitative analysis of growth patterns within and across species.
Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on mod... more Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on modern data acquisition and imaging technologies such as micro-computed or synchrotron tomography and interactive visualization. The acquired volume data sets are not only of high-resolution but in particular exhibit complex spatial structures at different levels of scale (e.g. variable spatial expression of multiscale periodic growth structures in tooth enamel). Such highly structured volume data sets represent a tough challenge to be analyzed and explored by means of interactive visualization due to the amount of raw volume data to be processed and filtered for the desired features. As an approach to address this bottleneck by multiscale feature preserving data reduction, we propose higher-order tensor approximations (TAs). We demonstrate the power of TA to represent, and highlight the structural features in volume data. We visually and quantitatively show that TA yields high data reducti...