Nick Milne - Academia.edu (original) (raw)
Papers by Nick Milne
Carnivory has evolved independently several times in eutherian (including placental) and metather... more Carnivory has evolved independently several times in eutherian (including placental) and metatherian (including marsupial) mammals. We used geometric morphometrics to assess convergences associated with the evolution of carnivory across a broad suite of mammals, including the eutherian clades Carnivora and Creodonta and the metatherian clades Thylacoleonidae, Dasyuromorphia, Didelphidae and Borhyaenoidea. We further quantified cranial disparity across eutherians and metatherians to test the hypothesis that the marsupial mode of reproduction has constrained their morphological evolution. This study, to our knowledge the first to extensively sample pre-Pleistocene taxa, analysed 30 three-dimensional landmarks, focused mainly on the facial region, which were digitized on 130 specimens, including 36 fossil taxa. Data were analysed with principal components (PC) analysis, and three measures of disparity were compared between eutherians and metatherians. PC1 showed a shift from short to long faces and seemed to represent diet and ecology. PC2 was dominated by the unique features of sabre-toothed forms: dramatic expansion of the maxilla at the expense of the frontal bones. PC3, in combination with PC1, distinguished metatherians and eutherians. Metatherians, despite common comparisons with felids, were more similar to caniforms, which was unexpected for taxa such as the sabre-toothed marsupial Thylacosmilus. Contrary to previous studies, metatherian carnivores consistently exhibited disparity which exceeded that of the much more speciose eutherian carnivore radiations, refuting the hypothesis that developmental constraints have limited the morphological evolution of the marsupial cranium.
Journal of Zoology, 2015
ABSTRACT
ABSTRACT stresses in trabeculae
uniformity of stress @ a surface may be a parameter rel.d to adaptive bone remodelling
biomech explanation for normal pits and tubercles at entheses
This study investigated sexual dimorphism in body size and limb proportions in relation to mating... more This study investigated sexual dimorphism in body size and limb proportions in relation to mating systems among the Macropodidae. Species were categorised into monogamous, polygynous or promiscuous mating systems based on existing literature. Linear measurements of crania and limb bones of over 1600 museum specimens across 32 species were taken, and functional indices were calculated. Cranial lengths were adjusted for age (molar index) using linear regression for each species, and means for each sex were taken. These means were highly correlated with published data on species' mass. Indices did not change with age, enabling calculation of male and female species means. Dimorphism within a species was represented by male-to-female ratios of mean cranial lengths and indices. Dimorphism in cranial length, tibioradial index and metatarso-radial ratio increased significantly across mating systems, with a weak trend observed in intermembral index also. This corresponds with increased ...
This study investigated sexual dimorphism in body size and limb proportions in relation to mating... more This study investigated sexual dimorphism in body size and limb proportions in relation to mating systems among the Macropodidae. Species were categorised into monogamous, polygynous or promiscuous mating systems based on existing literature. Linear measurements of crania and limb bones of over 1600 sexed museum specimens across 32 species were taken, and functional indices of the limbs were calculated. Cranial lengths were adjusted for age (molar index) using linear regression for each species, and means for each sex were taken. These means were highly correlated with published data on species' mass. Indices did not change with age, enabling calculation of male and female species means. Dimorphism within a species was represented by male-to-female ratios of mean cranial lengths and indices. Dimorphism in cranial length, tibioradial index and metatarso-radial ratio increased significantly across mating systems, with a weak trend observed in intermembral index also. This correspo...
Evolutionary Biology, 2015
Among closely related species, larger mammals tend to have a longer face and proportionally small... more Among closely related species, larger mammals tend to have a longer face and proportionally smaller braincase. This putative 'rule' in mammalian macroevolution has been proposed for the first time in 2013 based on 3D geometric morphometrics of antelopes, fruit bats, tree squirrels and mongooses. To firmly demonstrate that this trend holds as a 'rule' requires expanding the analysis in more lineages and other mammalian orders: if supported in most groups, it may indeed become a new evolutionary 'rule' besides famous ones such as Bergmann's and Allen's. In this study, using statistical shape analysis and both standard and comparative methods on a sample of kangaroos, wallabies and other macropodine marsupials, we show that the 'big size-long face' pattern is indeed found also outside the placentals. This provides support to the hypothesis of an important role of size-related shape changes (i.e., allometry) in the origin of the exceptional disparity of mammals, that, only in terms of size, span more orders of magnitude than any other animal: from 3 to 4 g of a tiny bat to more than 100 tons in blue whales.
Australian Journal of Zoology, 2014
The western grey kangaroo, Macropus fuliginosus, is a large-bodied kangaroo that engages in penta... more The western grey kangaroo, Macropus fuliginosus, is a large-bodied kangaroo that engages in pentapedal locomotion at low speeds and bipedal hopping at high speeds. The tail is thought to have functional roles in both of these modes of locomotion. In pentapedal locomotion the tail acts as a 'fifth limb' to support the body weight together with the forelimbs while the hind limbs are drawn forward. The tail has also been suggested to have a role as a counterbalance during bipedal hopping. On the basis of these functional roles for the tail in locomotion, the caudal musculature of the western grey kangaroo was dissected and described in this study. The arrangement of the caudal musculature showed particular adaptations for the role of the tail in both pentapedal locomotion and bipedal hopping.
ABSTRACT Osteoarthritis is synonymous to the functional disorder of articular cartilage. Mechanic... more ABSTRACT Osteoarthritis is synonymous to the functional disorder of articular cartilage. Mechanical tests of articular cartilage offer a way to understand the tissue's functionality and osteoarthritis. During normal activities, chondrocytes (cells) are indirectly exposed to varied mechanical compressions exerted on articular cartilage. Study of the morphological response of chondrocytes to the mechanical compressions exerted on articular cartilage offers understanding the physical integrity of chondrocytes, and initial physiological change of articular cartilage for detecting early osteoarthritis. Fibre optic confocal microscopy uses fibre optic imaging technologies to study the internal microstructure of bulk articular cartilage. The technologies have led to develop confocal arthroscopy for in vivo studying the cellular structure of articular cartilage. Using fibre optic laser confocal microscopy and a developed computer image analysis software, we studied the morphological response of the chondrocytes in the superficial and transitional zone to the uniaxial compression of articular cartilage at 0.25MPa and 0.5MPa. The results suggest that the mechanical compression exerted on articular cartilage caused morphological changes of the chondrocytes, which can be measured by the technique described in this study. The technique developed in this study shows potential to develop a methodology for in vivo studying the physiological integrity of chondrocyte and early osteoarthritis.
Visual Communication, 2011
Abstract Traditional portraiture aims to produce a life-like representation of an individual'... more Abstract Traditional portraiture aims to produce a life-like representation of an individual's unique facial features, but there are a number of perceptual factors that may affect how an artist sees and depicts a sitter's facial shapes. The anatomical accuracy of a portrait is ...
Spine, 1996
Vertebral morphology of the cervicothoracic junctional region was studied using the C6 to T4 vert... more Vertebral morphology of the cervicothoracic junctional region was studied using the C6 to T4 vertebrae from 51 disarticulated skeletons (26 males and 25 females). Orientation of the facet joint pair relative to the plane of the superior endplate and the sagittal reference was recorded. A vertebral index was developed to compare the superior endplate surface area with the posterior vertebral body height. Vertebral morphometry was recorded for comparison with the limited published data for this region. The disc-facet angle was measured using a zygapophysial endplate protractor and the facet angle recorded from computer-aided digitizing of photographs of each segment. Vertebral dimensions were measured using Mitutoyo digital calipers. A marked change in disc-facet angle from C6 to T1 was recorded, with the incidence of right versus left asymmetry highest at the T1 level. The incidence of facet angle asymmetry greater than 10 degrees was 24% at C6, 18% at C7, and 16% at T1. The vertebral index indicated no significant gender difference. Consistent with other junctional regions of the spine, the cervicothoracic transition has significant morphological variations.
Proceedings of the Royal Society B: Biological Sciences, 2012
How animals cope with increases in body size is a key issue in biology. Here, we consider scaling... more How animals cope with increases in body size is a key issue in biology. Here, we consider scaling of xenarthrans, particularly how femoral form and function varies to accommodate the size range between the 3 kg armadillo and its giant relative the 300 kg glyptodont. It has already been noted that femoral morphology differs between these animals and suggested that this reflects a novel adaptation to size increase in glyptodont. We test this idea by applying a finite element analysis of coronal plane forces to femoral models of these animals, simulating the stance phase in the hind limb; where the femur is subject to bending owing to longitudinal compressive as well as abduction loads on the greater trochanter. We use these models to examine the hypothesis that muscles attaching on the third trochanter (T3) can reduce this bending in the loaded femur and that the T3 forces are more effective at reducing bending in glyptodont where the T3 is situated at the level of the knee. The analysis uses traditional finite element methods to produce strain maps and examine strains at 200 points on the femur. The coordinates of these points before and after loading are also used to carry out geometric morphometric (GM) analyses of the gross deformation of the model in different loading scenarios. The results show that longitudinal compressive and abductor muscle loading increases bending in the coronal plane, and that loads applied to the T3 reduce that bending. In the glyptodont model, the T3 loads are more effective and can more readily compensate for the bending owing to longitudinal and abductor loads. This study also demonstrates the usefulness of GM methods in interpreting the results of finite element analyses.
Primates, 2008
In order to understand how mandibular structure differs among the Chinese cercopithecoids (Rhinop... more In order to understand how mandibular structure differs among the Chinese cercopithecoids (Rhinopithecus, Trachypithecus and Macaca), particularly the uniqueness of the snub-nosed monkeys (Rhinopithecus), we analysed ten mandibular measurements by principal components analysis (PCA), and examined scaling patterns. The results provided by the PCA illustrated differences due to size among the cercopithecoids and the relationship between colobines (Trachypithecus and Rhinopithecus) and cercopithecines, in which macaques (Macaca) are included. Allometric analysis indicated that, biomechanically, there is not a marked difference between macaques and leaf-eating monkeys. This may be associated with the fact that both share some similar ecology and niches in south and southwest China. The snub-nosed monkeys exhibit a significantly more robust mandible, evident in the symphysis, corpus, condyle, and masticatory momentum arm. This supports the hypothesis, based on the study of dental structure, that Rhinopithecus is a unique group in Asian Old World monkeys (OWMs) and has developed some unique characteristics in order to adapt to the tough food available in the severe cold climate of the Plateaux of Qinghai-Tibet, Yun-Gui and Qingling in China.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2006
The Santacrucian (early-middle Miocene) fauna is exceptional in its richness (over 70 species rec... more The Santacrucian (early-middle Miocene) fauna is exceptional in its richness (over 70 species recorded in 21 stratigraphic levels). In this contribution we attempt a preliminary paleobiological characterization of the armadillos (Dasypodidae and Peltephilidae). Santacrucian Dasypodidae includes the genera Prozaedyus Ameghino, Proeutatus Ameghino, Stenotatus Ameghino, and Stegotherium Ameghino. The Peltephilidae include the genus Peltephilus Ameghino and others undergoing systematic revision. Body masses and locomotory habits are inferred from the sizes of the proximal and middle shaft dimensions of the limb bones from allometric equations and indices previously modeled in living dasypodids. Masticatory and dietary interpretations are based on the jaw mechanics, the analysis of the temporomandibular joint and mandibular symphysis, and the shape, arrangement and wear patterns of teeth. The body mass averages are 15.28 kg for Proeutatus, 3.72 kg for Stenotatus, 1.12 kg for Prozaedyus, 11.47 for Stegotherium, and 11.07 kg for Peltephilus. The diversity in limb bone proportions is not so marked as in the living species; forelimb indices reflect proportions similar to those of the living dasypodines and euphractines, all of whom are relatively good diggers. None of the Santacrucian taxa reach the degree of cursoriality of Tolypeutes Illiger, the extreme fossoriality of Priodontes F. Cuvier, or the subterranean habits of Chlamyphorus Harlan. Within a potentially generalized omnivory, some specializations can be easily detected within the Santacrucian armadillos: herbivory in Proeutatus and Peltephilus, and myrmecophagy in Stegotherium. This could help to explain the potential coexistence of so many genera in a single area, diminishing the degree of competition for resources. D
Manual Therapy, 1998
S UMMA R Y. There have been no reports describing the pattern of degenerative changes of spinal s... more S UMMA R Y. There have been no reports describing the pattern of degenerative changes of spinal segments within the cervicothoracic (CT) transitional junction. To address this deficiency, intervertebral disc degenerative changes in this region were studied between the C6 to T4 vertebrae, using hemisected spinal columns from 96 individuals (69 male and 27 female). Sagittally sectioned spinal columns were inspected macroscopicaily by one observer and graded using previously reported grading scales. In addition, endplate irregularity, intervertebral disc degenerative changes, discal splitting and vertebral body marginal osteophytes were recorded. Combining all classifications of degeneration, the frequency of disc degeneration at C6-C7 was 49%, C7-T1 = 42%, T1-T2 = 40%, T2-T3 = 50% and T3-T4 = 44%. Significant age trends were noted, with 25% of all discs showing degeneration in the youngest group, compared to 58% in the oldest group. The incidence of disc degenerative changes through this transition declined from the C6-C7 to the T1-T2 segments but increased slightly for the more severe changes at the T2-T3 and T3-T4 segments. In one third of cases demonstrating degenerative discal changes no evidence of osteophyte formation was present. The manual therapist should not exclude the possibility of discal pathology in patients presenting with cervicothoracic pain, particularly if the patient is over 30 years of age.
Lethaia, 2011
1. Sergio F. Vizcaíno [vizcaino@ fcnym. unlp. edu. ar], División Paleontología Vertebrados, Museo... more 1. Sergio F. Vizcaíno [vizcaino@ fcnym. unlp. edu. ar], División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, B1900FWA La Plata, Argentina, CONICET; R. Ernesto Blanco [ernesto@ fisica. edu. uy], Instituto de Física, Facultad de Ciencias, Iguá ...
Journal of Zoology, 2013
Hypertrophied canines evolved several times among mammalian carnivores. Several palaeobiological ... more Hypertrophied canines evolved several times among mammalian carnivores. Several palaeobiological hypotheses related to sabretooth evolution and killing behaviours have been suggested based on biomechanical and functional considerations. However, the lack of well-studied extant analogues makes it difficult to test these hypotheses. Here we propose the South American short-tailed opossum Monodelphis dimidiata as a living analogue of extinct sabretooth predators. Our morphological analysis shows that M. dimidiata not only has relatively the largest canines among extant marsupial carnivores, but they are also within the range of those of sabretooth predators. It also has cranial adaptations for a wide gape typical of sabretooth carnivores. The small body size of this species allows further biological studies that can provide useful information to understand the evolution, behaviour and physiology of extinct sabretooth carnivores.
Carnivory has evolved independently several times in eutherian (including placental) and metather... more Carnivory has evolved independently several times in eutherian (including placental) and metatherian (including marsupial) mammals. We used geometric morphometrics to assess convergences associated with the evolution of carnivory across a broad suite of mammals, including the eutherian clades Carnivora and Creodonta and the metatherian clades Thylacoleonidae, Dasyuromorphia, Didelphidae and Borhyaenoidea. We further quantified cranial disparity across eutherians and metatherians to test the hypothesis that the marsupial mode of reproduction has constrained their morphological evolution. This study, to our knowledge the first to extensively sample pre-Pleistocene taxa, analysed 30 three-dimensional landmarks, focused mainly on the facial region, which were digitized on 130 specimens, including 36 fossil taxa. Data were analysed with principal components (PC) analysis, and three measures of disparity were compared between eutherians and metatherians. PC1 showed a shift from short to long faces and seemed to represent diet and ecology. PC2 was dominated by the unique features of sabre-toothed forms: dramatic expansion of the maxilla at the expense of the frontal bones. PC3, in combination with PC1, distinguished metatherians and eutherians. Metatherians, despite common comparisons with felids, were more similar to caniforms, which was unexpected for taxa such as the sabre-toothed marsupial Thylacosmilus. Contrary to previous studies, metatherian carnivores consistently exhibited disparity which exceeded that of the much more speciose eutherian carnivore radiations, refuting the hypothesis that developmental constraints have limited the morphological evolution of the marsupial cranium.
Journal of Zoology, 2015
ABSTRACT
ABSTRACT stresses in trabeculae
uniformity of stress @ a surface may be a parameter rel.d to adaptive bone remodelling
biomech explanation for normal pits and tubercles at entheses
This study investigated sexual dimorphism in body size and limb proportions in relation to mating... more This study investigated sexual dimorphism in body size and limb proportions in relation to mating systems among the Macropodidae. Species were categorised into monogamous, polygynous or promiscuous mating systems based on existing literature. Linear measurements of crania and limb bones of over 1600 museum specimens across 32 species were taken, and functional indices were calculated. Cranial lengths were adjusted for age (molar index) using linear regression for each species, and means for each sex were taken. These means were highly correlated with published data on species' mass. Indices did not change with age, enabling calculation of male and female species means. Dimorphism within a species was represented by male-to-female ratios of mean cranial lengths and indices. Dimorphism in cranial length, tibioradial index and metatarso-radial ratio increased significantly across mating systems, with a weak trend observed in intermembral index also. This corresponds with increased ...
This study investigated sexual dimorphism in body size and limb proportions in relation to mating... more This study investigated sexual dimorphism in body size and limb proportions in relation to mating systems among the Macropodidae. Species were categorised into monogamous, polygynous or promiscuous mating systems based on existing literature. Linear measurements of crania and limb bones of over 1600 sexed museum specimens across 32 species were taken, and functional indices of the limbs were calculated. Cranial lengths were adjusted for age (molar index) using linear regression for each species, and means for each sex were taken. These means were highly correlated with published data on species' mass. Indices did not change with age, enabling calculation of male and female species means. Dimorphism within a species was represented by male-to-female ratios of mean cranial lengths and indices. Dimorphism in cranial length, tibioradial index and metatarso-radial ratio increased significantly across mating systems, with a weak trend observed in intermembral index also. This correspo...
Evolutionary Biology, 2015
Among closely related species, larger mammals tend to have a longer face and proportionally small... more Among closely related species, larger mammals tend to have a longer face and proportionally smaller braincase. This putative 'rule' in mammalian macroevolution has been proposed for the first time in 2013 based on 3D geometric morphometrics of antelopes, fruit bats, tree squirrels and mongooses. To firmly demonstrate that this trend holds as a 'rule' requires expanding the analysis in more lineages and other mammalian orders: if supported in most groups, it may indeed become a new evolutionary 'rule' besides famous ones such as Bergmann's and Allen's. In this study, using statistical shape analysis and both standard and comparative methods on a sample of kangaroos, wallabies and other macropodine marsupials, we show that the 'big size-long face' pattern is indeed found also outside the placentals. This provides support to the hypothesis of an important role of size-related shape changes (i.e., allometry) in the origin of the exceptional disparity of mammals, that, only in terms of size, span more orders of magnitude than any other animal: from 3 to 4 g of a tiny bat to more than 100 tons in blue whales.
Australian Journal of Zoology, 2014
The western grey kangaroo, Macropus fuliginosus, is a large-bodied kangaroo that engages in penta... more The western grey kangaroo, Macropus fuliginosus, is a large-bodied kangaroo that engages in pentapedal locomotion at low speeds and bipedal hopping at high speeds. The tail is thought to have functional roles in both of these modes of locomotion. In pentapedal locomotion the tail acts as a 'fifth limb' to support the body weight together with the forelimbs while the hind limbs are drawn forward. The tail has also been suggested to have a role as a counterbalance during bipedal hopping. On the basis of these functional roles for the tail in locomotion, the caudal musculature of the western grey kangaroo was dissected and described in this study. The arrangement of the caudal musculature showed particular adaptations for the role of the tail in both pentapedal locomotion and bipedal hopping.
ABSTRACT Osteoarthritis is synonymous to the functional disorder of articular cartilage. Mechanic... more ABSTRACT Osteoarthritis is synonymous to the functional disorder of articular cartilage. Mechanical tests of articular cartilage offer a way to understand the tissue's functionality and osteoarthritis. During normal activities, chondrocytes (cells) are indirectly exposed to varied mechanical compressions exerted on articular cartilage. Study of the morphological response of chondrocytes to the mechanical compressions exerted on articular cartilage offers understanding the physical integrity of chondrocytes, and initial physiological change of articular cartilage for detecting early osteoarthritis. Fibre optic confocal microscopy uses fibre optic imaging technologies to study the internal microstructure of bulk articular cartilage. The technologies have led to develop confocal arthroscopy for in vivo studying the cellular structure of articular cartilage. Using fibre optic laser confocal microscopy and a developed computer image analysis software, we studied the morphological response of the chondrocytes in the superficial and transitional zone to the uniaxial compression of articular cartilage at 0.25MPa and 0.5MPa. The results suggest that the mechanical compression exerted on articular cartilage caused morphological changes of the chondrocytes, which can be measured by the technique described in this study. The technique developed in this study shows potential to develop a methodology for in vivo studying the physiological integrity of chondrocyte and early osteoarthritis.
Visual Communication, 2011
Abstract Traditional portraiture aims to produce a life-like representation of an individual'... more Abstract Traditional portraiture aims to produce a life-like representation of an individual's unique facial features, but there are a number of perceptual factors that may affect how an artist sees and depicts a sitter's facial shapes. The anatomical accuracy of a portrait is ...
Spine, 1996
Vertebral morphology of the cervicothoracic junctional region was studied using the C6 to T4 vert... more Vertebral morphology of the cervicothoracic junctional region was studied using the C6 to T4 vertebrae from 51 disarticulated skeletons (26 males and 25 females). Orientation of the facet joint pair relative to the plane of the superior endplate and the sagittal reference was recorded. A vertebral index was developed to compare the superior endplate surface area with the posterior vertebral body height. Vertebral morphometry was recorded for comparison with the limited published data for this region. The disc-facet angle was measured using a zygapophysial endplate protractor and the facet angle recorded from computer-aided digitizing of photographs of each segment. Vertebral dimensions were measured using Mitutoyo digital calipers. A marked change in disc-facet angle from C6 to T1 was recorded, with the incidence of right versus left asymmetry highest at the T1 level. The incidence of facet angle asymmetry greater than 10 degrees was 24% at C6, 18% at C7, and 16% at T1. The vertebral index indicated no significant gender difference. Consistent with other junctional regions of the spine, the cervicothoracic transition has significant morphological variations.
Proceedings of the Royal Society B: Biological Sciences, 2012
How animals cope with increases in body size is a key issue in biology. Here, we consider scaling... more How animals cope with increases in body size is a key issue in biology. Here, we consider scaling of xenarthrans, particularly how femoral form and function varies to accommodate the size range between the 3 kg armadillo and its giant relative the 300 kg glyptodont. It has already been noted that femoral morphology differs between these animals and suggested that this reflects a novel adaptation to size increase in glyptodont. We test this idea by applying a finite element analysis of coronal plane forces to femoral models of these animals, simulating the stance phase in the hind limb; where the femur is subject to bending owing to longitudinal compressive as well as abduction loads on the greater trochanter. We use these models to examine the hypothesis that muscles attaching on the third trochanter (T3) can reduce this bending in the loaded femur and that the T3 forces are more effective at reducing bending in glyptodont where the T3 is situated at the level of the knee. The analysis uses traditional finite element methods to produce strain maps and examine strains at 200 points on the femur. The coordinates of these points before and after loading are also used to carry out geometric morphometric (GM) analyses of the gross deformation of the model in different loading scenarios. The results show that longitudinal compressive and abductor muscle loading increases bending in the coronal plane, and that loads applied to the T3 reduce that bending. In the glyptodont model, the T3 loads are more effective and can more readily compensate for the bending owing to longitudinal and abductor loads. This study also demonstrates the usefulness of GM methods in interpreting the results of finite element analyses.
Primates, 2008
In order to understand how mandibular structure differs among the Chinese cercopithecoids (Rhinop... more In order to understand how mandibular structure differs among the Chinese cercopithecoids (Rhinopithecus, Trachypithecus and Macaca), particularly the uniqueness of the snub-nosed monkeys (Rhinopithecus), we analysed ten mandibular measurements by principal components analysis (PCA), and examined scaling patterns. The results provided by the PCA illustrated differences due to size among the cercopithecoids and the relationship between colobines (Trachypithecus and Rhinopithecus) and cercopithecines, in which macaques (Macaca) are included. Allometric analysis indicated that, biomechanically, there is not a marked difference between macaques and leaf-eating monkeys. This may be associated with the fact that both share some similar ecology and niches in south and southwest China. The snub-nosed monkeys exhibit a significantly more robust mandible, evident in the symphysis, corpus, condyle, and masticatory momentum arm. This supports the hypothesis, based on the study of dental structure, that Rhinopithecus is a unique group in Asian Old World monkeys (OWMs) and has developed some unique characteristics in order to adapt to the tough food available in the severe cold climate of the Plateaux of Qinghai-Tibet, Yun-Gui and Qingling in China.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2006
The Santacrucian (early-middle Miocene) fauna is exceptional in its richness (over 70 species rec... more The Santacrucian (early-middle Miocene) fauna is exceptional in its richness (over 70 species recorded in 21 stratigraphic levels). In this contribution we attempt a preliminary paleobiological characterization of the armadillos (Dasypodidae and Peltephilidae). Santacrucian Dasypodidae includes the genera Prozaedyus Ameghino, Proeutatus Ameghino, Stenotatus Ameghino, and Stegotherium Ameghino. The Peltephilidae include the genus Peltephilus Ameghino and others undergoing systematic revision. Body masses and locomotory habits are inferred from the sizes of the proximal and middle shaft dimensions of the limb bones from allometric equations and indices previously modeled in living dasypodids. Masticatory and dietary interpretations are based on the jaw mechanics, the analysis of the temporomandibular joint and mandibular symphysis, and the shape, arrangement and wear patterns of teeth. The body mass averages are 15.28 kg for Proeutatus, 3.72 kg for Stenotatus, 1.12 kg for Prozaedyus, 11.47 for Stegotherium, and 11.07 kg for Peltephilus. The diversity in limb bone proportions is not so marked as in the living species; forelimb indices reflect proportions similar to those of the living dasypodines and euphractines, all of whom are relatively good diggers. None of the Santacrucian taxa reach the degree of cursoriality of Tolypeutes Illiger, the extreme fossoriality of Priodontes F. Cuvier, or the subterranean habits of Chlamyphorus Harlan. Within a potentially generalized omnivory, some specializations can be easily detected within the Santacrucian armadillos: herbivory in Proeutatus and Peltephilus, and myrmecophagy in Stegotherium. This could help to explain the potential coexistence of so many genera in a single area, diminishing the degree of competition for resources. D
Manual Therapy, 1998
S UMMA R Y. There have been no reports describing the pattern of degenerative changes of spinal s... more S UMMA R Y. There have been no reports describing the pattern of degenerative changes of spinal segments within the cervicothoracic (CT) transitional junction. To address this deficiency, intervertebral disc degenerative changes in this region were studied between the C6 to T4 vertebrae, using hemisected spinal columns from 96 individuals (69 male and 27 female). Sagittally sectioned spinal columns were inspected macroscopicaily by one observer and graded using previously reported grading scales. In addition, endplate irregularity, intervertebral disc degenerative changes, discal splitting and vertebral body marginal osteophytes were recorded. Combining all classifications of degeneration, the frequency of disc degeneration at C6-C7 was 49%, C7-T1 = 42%, T1-T2 = 40%, T2-T3 = 50% and T3-T4 = 44%. Significant age trends were noted, with 25% of all discs showing degeneration in the youngest group, compared to 58% in the oldest group. The incidence of disc degenerative changes through this transition declined from the C6-C7 to the T1-T2 segments but increased slightly for the more severe changes at the T2-T3 and T3-T4 segments. In one third of cases demonstrating degenerative discal changes no evidence of osteophyte formation was present. The manual therapist should not exclude the possibility of discal pathology in patients presenting with cervicothoracic pain, particularly if the patient is over 30 years of age.
Lethaia, 2011
1. Sergio F. Vizcaíno [vizcaino@ fcnym. unlp. edu. ar], División Paleontología Vertebrados, Museo... more 1. Sergio F. Vizcaíno [vizcaino@ fcnym. unlp. edu. ar], División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, B1900FWA La Plata, Argentina, CONICET; R. Ernesto Blanco [ernesto@ fisica. edu. uy], Instituto de Física, Facultad de Ciencias, Iguá ...
Journal of Zoology, 2013
Hypertrophied canines evolved several times among mammalian carnivores. Several palaeobiological ... more Hypertrophied canines evolved several times among mammalian carnivores. Several palaeobiological hypotheses related to sabretooth evolution and killing behaviours have been suggested based on biomechanical and functional considerations. However, the lack of well-studied extant analogues makes it difficult to test these hypotheses. Here we propose the South American short-tailed opossum Monodelphis dimidiata as a living analogue of extinct sabretooth predators. Our morphological analysis shows that M. dimidiata not only has relatively the largest canines among extant marsupial carnivores, but they are also within the range of those of sabretooth predators. It also has cranial adaptations for a wide gape typical of sabretooth carnivores. The small body size of this species allows further biological studies that can provide useful information to understand the evolution, behaviour and physiology of extinct sabretooth carnivores.