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Jon H. Kaas - One of the best experts on this subject based on the ideXlab platform.
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differential expression patterns of striate cortex enriched genes among old world new world and Prosimian primates
Cerebral Cortex, 2012Co-Authors: Toru Takahata, Rammohan Shukla, Tetsuo Yamamori, Jon H. KaasAbstract:A group of 5 genes, OCC1, testican-1, testican-2, 5-HT1B, and 5-HT2A, are selectively expressed in layer 4 (4C of Brodmann) of striate cortex (visual area V1) of both Old World macaques and New World marmoset monkeys. The expression of these genes is activity dependent, as expression is reduced after blocking retinal activity. Surprisingly, the pronounced expression pattern has not been found in rodents or carnivores. Thus, these genes may be highly expressed in V1 of some but perhaps not all primates. Here, we compared the gene expression in members of 3 major branches of primate evolution: Prosimians, New World monkeys, and Old World monkeys. Although the expression pattern of 5-HT1B was well conserved, those of the other genes varied from the least distinct in Prosimian galagos to successively more in New World owl monkeys, marmosets, squirrel monkeys, and Old World macaque monkeys. In owl monkeys, the expression of 5-HT2A was significantly reduced by monocular tetrodotoxin injection, while those of OCC1 and 5-HT1B were not. Thus, we propose that early primates had low levels of expression and higher levels emerged with anthropoid primates and became further enhanced in the Old World catarrhine monkeys that are more closely related to humans.
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cortical projections to the superior colliculus in Prosimian galagos otolemur garnetti
The Journal of Comparative Neurology, 2012Co-Authors: Mary K L Baldwin, Jon H. KaasAbstract:The superior colliculus (SC) is a key structure within the extrageniculate pathway of visual information to cortex and is highly involved in visuomotor functions. Previous studies in anthropoid primates have shown that superficial layers of the SC receive direct inputs from various visual cortical areas such as V1, V2, and middle temporal (MT), while deeper layers receive direct inputs from visuomotor cortical areas within the posterior parietal cortex and the frontal eye fields. Very little is known, however, about the corticotectal projections in Prosimian primates. In the current study we investigated the sources of cortical inputs to the SC in Prosimian galagos (Otolemur garnetti) using retrograde anatomical tracers placed into the SC. The superficial layers of the SC in galagos received the majority of their inputs from early visual areas and visual areas within the MT complex. Yet, surprisingly, MT itself had relatively few corticotectal projections. Deeper layers of the SC received direct projections from visuomotor areas including the posterior parietal cortex and premotor cortex. However, relatively few corticotectal projections originated within the frontal eye fields. While Prosimian galagos resemble other primates in having early visual areas project to the superficial layers of the SC, with higher visuomotor regions projecting to deeper layers, the results suggest that MT and frontal eye field projections to the SC were sparse in early primates, remained sparse in present-day Prosimian primates, and became more pronounced in anthropoid primates.
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Neuron densities vary across and within cortical areas in primates
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Christine E Collins, David C. Airey, Nicole A. Young, Duncan B Leitch, Jon H. KaasAbstract:The numbers and proportion of neurons in areas and regions of cortex were determined for a single cortical hemisphere from two Prosimian galagos, one New World owl monkey, one Old World macaque monkey, and one baboon. The results suggest that there is a common plan of cortical organization across the species examined here and also differences that suggest greater specializations in the Old World monkeys. In all primates examined, primary visual cortex (V1) was the most neuron-dense cortical area and the secondary visual areas had higher-than-average densities. Primary auditory and somatosensory areas tended to have high densities in the Old World macaque and baboon. Neuronal density varies less across cortical areas in Prosimian galagos than in the Old World monkeys. Thus, cortical architecture varies greatly within and across primate species, but cell density is greater in cortex devoted to the early stages of sensory processing.
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cortical connections of the visual pulvinar complex in Prosimian galagos otolemur garnetti
The Journal of Comparative Neurology, 2009Co-Authors: Peiyan Wong, Christine E Collins, Mary K L Baldwin, Jon H. KaasAbstract:The present study focuses on determining the cortical and tectal connections with subdivisions of the visual pulvinar in Prosimian galagos. Traditionally, the pulvinar complex of primates has been divided into inferior (PI), lateral (PL), and medial (PM) regions (Stepniewska and Kaas, 1997; Stepniewska et al., 1999; Kaas and Lyon, 2007; Jones, 2007). The inferior pulvinar, once thought to be a single nucleus, has been divided into four nuclei in monkeys that can be distinguished by histochemical differences and patterns of projections to areas of visual cortex (for review see Kaas and Lyon, 2007). In monkeys, the most lateral part of PI, the large central lateral nucleus (PIcl), projects to primary and secondary visual areas, V1 and V2, as well as the dorsolateral visual area (DL or V4), whereas a smaller, medial nucleus (PIm) projects to the middle temporal visual area, MT. The posterior (PIp) and central medial (PIcm) nuclei receive inputs from the superior colliculus and project to areas of the dorsal stream of visual processing that are connected with MT. The lateral pulvinar largely consists of a large ventral lateral nucleus (PLvl) that projects to V1, V2, and DL(V4). A dorsomedial nucleus (PLdm) is sometimes distinguished as part of the lateral pulvinar, but its connections with prefrontal and inferior parietal cortex suggest that it more appropriately should be considered part of the medial pulvinar, which has widespread connections that are not strictly visual. An anterior or oral pulvinar is associated with somatosensory cortex and clearly is not part of the visual pulvinar. The visual pulvinar (also called the lateral posterior nucleus or the lateral posterior pulvinar complex) appears to be organized somewhat differently in carnivores, rodents (Jones, 2007), and even tree shrews (Lyon et al., 2003), and common (homologous) nuclei have been difficult to identify. Understanding of the visual pulvinar organization in primates has largely been based on studies of New and Old World monkeys (see e.g., Allman et al., 1972; Gattass et al., 1978; Lin and Kaas, 1979; Bender, 1981; Ungerleider et al., 1983; Boussaoud et al., 1992; Cusick et al., 1993; Gutierrez et al., 1995; Gutierrez and Cusick, 1997; Stepniewska and Kaas, 1997; Stepniewska et al., 1999, 2000; Gray et al., 1999; Adams et al., 2000; O’Brien et al., 2001; Shipp, 2001; Weller et al., 2002; Cola et al., 2005), where major similarities in architectonic subdivisions and connection patterns are evident. However, little is known about the organization of the visual pulvinar in other primates. Broader comparisons across mammalian taxa might result in a fuller understanding of common and variable features of visual pulvinar organization across the major branches of the primate radiation. Toward this end, we sought to reveal patterns of visual pulvinar connections in a member of the Prosimian radiation, the Otolemur garnetti. The primate order has three major branches, the Prosimians, the tarsiers, and the anthropoid primates that include monkeys, apes, and humans. In general, the skull and brain shapes of extant Prosimian (strepsirrhine) primates resemble those of the earliest primate fossils (Radinsky, 1977; Jerison, 1979), suggesting that, in some respects, Prosimian brains have changed the least in primate evolution. An initial separation of the two main branches of early Prosimians into lemuriforms and lorisiforms occurred in Africa 50 – 80 million years ago. The lemuriform ancestor invaded Madagascar to initiate the highly varied radiation of lemurs (Horvath and Willard, 2007), and lorisiforms divided into lorisides and galagosides (Roos et al., 2004). The galagos, including Otolemur garnetti (formerly Galago garnetti), remained in Africa, whereas one of the two lorisid lineages migrated to Asia. Most of what is known about the organization of Prosimian brains comes from studies of galagos. Previously, several papers have described some aspects of pulvinar connections in galagos (Glendenning et al., 1975; Raczkowski and Diamond, 1978, 1980, 1981; Symonds and Kaas, 1978; Carey et al., 1979; Wall et al., 1982). The present results, together with previous findings, allow a more comprehensive understanding of pulvinar organization in galagos as well as a comparison with what is now known about pulvinar organization in monkeys. The major conclusion stemming from this comparison is that the inferior pulvinar of galagos, and perhaps other Prosimians, has fewer subdivisions than in monkeys, and cortical connections with various visual cortical areas are not as segregated. The cortical areas investigated in the present study include V1 and V2, areas common to most mammals, and MT, an area characteristic of all primates with no obvious homologue in other mammals (Kaas, 2004). In addition, we describe superior colliculus projections to the pulvinar.
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cortical connections of the middle temporal and the middle temporal crescent visual areas in Prosimian galagos otolemur garnetti
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2007Co-Authors: Peter M Kaskan, Jon H. KaasAbstract:While considerable progress has been made in understanding the organization of visual cortex in monkeys, less is known about the visual systems of Prosimians. The middle temporal visual area (MT), an area involved in motion perception, is common to all primates. We placed injections of tracers in MT and just caudal to MT in cortex expected to be the MT crescent (MTc), an area previously identified in monkeys but not in Prosimians. We analyzed the patterns of projections in sections of the flattened cortex and used sections stained for cytochrome oxidase (CO) and myelin to identify the borders of MT, MTc, middle superior temporal (MST), superior temporal sulcus (FST), and V1 and V2 and to identify possible subdivisions of these areas. As in owl monkeys, MTc is a belt around most of MT that consists of a single row of CO-dense patches in a CO-light surround. Injections placed in MT revealed connections with V1, V2, V3, FST, MST, MTc, dorsomedial, dorsolateral (DL), posterior parietal cortex, and inferotemporal (IT) cortex. Injections localized to MTc displayed a slightly different pattern of connections with more involvement of DL and IT cortex, though other aspects, including patchy connections with V1 and V2, were similar to MT connections. The results indicate that Prosimian galagos have an MT area with connection patterns that are similar to those in New and Old World monkeys. The MTc, initially described in owl monkeys, is present in galagos and is likely to be a common component of primate visual cortex. Anat Rec 2007. © 2007 Wiley-Liss, Inc.
Peter M Kappeler - One of the best experts on this subject based on the ideXlab platform.
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patterns of sexual dimorphism in body weight among Prosimian primates
Folia Primatologica, 1991Co-Authors: Peter M KappelerAbstract:Many primatologists believe that there is no sexual dimorphism in body size in Prosimian primates. Because this belief is based upon data that came from only a few species and were largely flawed in s
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the evolution of sexual size dimorphism in Prosimian primates
American Journal of Primatology, 1990Co-Authors: Peter M KappelerAbstract:: The four major hypotheses advanced to explain the evolution of sexually dimorphic characters invoke sexual selection, natural selection, allometry, and phylogenetic inertia. In this paper, each of these hypotheses is examined for its usefulness in explaining the inter-specific variation in sexual size dimorphism among Prosimian primates. Data on body weight and the degree of sexual dimorphism were obtained for 32 Prosimian and 95 simian species. Although Prosimians exhibited significantly less sexual dimorphism than simians, there was nevertheless significant variation in dimorphism among them. The degree of sexual dimorphism in Prosimians did not show significant variance at any taxonomic level, but the majority of variance occurred within genera. Thus, sexual dimorphism in size among Prosimians is probably not constrained by phylogeny at the generic level and above. There was no significant correlation between body size and the degree of sexual dimorphism in Prosimians, suggesting the absence of an allometric effect. Similarly there was no relationship between body size and sexual dimorphism among simians in this size range. This result suggested that the expression of sexual dimorphism may nevertheless be influenced by absolute size. In Prosimians, inter-specific differences in sexual dimorphism were not correlated with variance in male reproductive success. It is suggested that speed and agility of males, rather than size and strength, might have been favored by intra-sexual selection in most Prosimians. It seems also plausible that the relative monomorphism of most Prosimians, especially in the Lemuriformes, might be a result of increased female size favored by natural selection. Consideration of all natural and sexual selective pressures that affect size in both sexes separately is required to understand the adaptive function and evolution of primate size dimorphism.
Christine E Collins - One of the best experts on this subject based on the ideXlab platform.
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Neuron densities vary across and within cortical areas in primates
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Christine E Collins, David C. Airey, Nicole A. Young, Duncan B Leitch, Jon H. KaasAbstract:The numbers and proportion of neurons in areas and regions of cortex were determined for a single cortical hemisphere from two Prosimian galagos, one New World owl monkey, one Old World macaque monkey, and one baboon. The results suggest that there is a common plan of cortical organization across the species examined here and also differences that suggest greater specializations in the Old World monkeys. In all primates examined, primary visual cortex (V1) was the most neuron-dense cortical area and the secondary visual areas had higher-than-average densities. Primary auditory and somatosensory areas tended to have high densities in the Old World macaque and baboon. Neuronal density varies less across cortical areas in Prosimian galagos than in the Old World monkeys. Thus, cortical architecture varies greatly within and across primate species, but cell density is greater in cortex devoted to the early stages of sensory processing.
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cortical connections of the visual pulvinar complex in Prosimian galagos otolemur garnetti
The Journal of Comparative Neurology, 2009Co-Authors: Peiyan Wong, Christine E Collins, Mary K L Baldwin, Jon H. KaasAbstract:The present study focuses on determining the cortical and tectal connections with subdivisions of the visual pulvinar in Prosimian galagos. Traditionally, the pulvinar complex of primates has been divided into inferior (PI), lateral (PL), and medial (PM) regions (Stepniewska and Kaas, 1997; Stepniewska et al., 1999; Kaas and Lyon, 2007; Jones, 2007). The inferior pulvinar, once thought to be a single nucleus, has been divided into four nuclei in monkeys that can be distinguished by histochemical differences and patterns of projections to areas of visual cortex (for review see Kaas and Lyon, 2007). In monkeys, the most lateral part of PI, the large central lateral nucleus (PIcl), projects to primary and secondary visual areas, V1 and V2, as well as the dorsolateral visual area (DL or V4), whereas a smaller, medial nucleus (PIm) projects to the middle temporal visual area, MT. The posterior (PIp) and central medial (PIcm) nuclei receive inputs from the superior colliculus and project to areas of the dorsal stream of visual processing that are connected with MT. The lateral pulvinar largely consists of a large ventral lateral nucleus (PLvl) that projects to V1, V2, and DL(V4). A dorsomedial nucleus (PLdm) is sometimes distinguished as part of the lateral pulvinar, but its connections with prefrontal and inferior parietal cortex suggest that it more appropriately should be considered part of the medial pulvinar, which has widespread connections that are not strictly visual. An anterior or oral pulvinar is associated with somatosensory cortex and clearly is not part of the visual pulvinar. The visual pulvinar (also called the lateral posterior nucleus or the lateral posterior pulvinar complex) appears to be organized somewhat differently in carnivores, rodents (Jones, 2007), and even tree shrews (Lyon et al., 2003), and common (homologous) nuclei have been difficult to identify. Understanding of the visual pulvinar organization in primates has largely been based on studies of New and Old World monkeys (see e.g., Allman et al., 1972; Gattass et al., 1978; Lin and Kaas, 1979; Bender, 1981; Ungerleider et al., 1983; Boussaoud et al., 1992; Cusick et al., 1993; Gutierrez et al., 1995; Gutierrez and Cusick, 1997; Stepniewska and Kaas, 1997; Stepniewska et al., 1999, 2000; Gray et al., 1999; Adams et al., 2000; O’Brien et al., 2001; Shipp, 2001; Weller et al., 2002; Cola et al., 2005), where major similarities in architectonic subdivisions and connection patterns are evident. However, little is known about the organization of the visual pulvinar in other primates. Broader comparisons across mammalian taxa might result in a fuller understanding of common and variable features of visual pulvinar organization across the major branches of the primate radiation. Toward this end, we sought to reveal patterns of visual pulvinar connections in a member of the Prosimian radiation, the Otolemur garnetti. The primate order has three major branches, the Prosimians, the tarsiers, and the anthropoid primates that include monkeys, apes, and humans. In general, the skull and brain shapes of extant Prosimian (strepsirrhine) primates resemble those of the earliest primate fossils (Radinsky, 1977; Jerison, 1979), suggesting that, in some respects, Prosimian brains have changed the least in primate evolution. An initial separation of the two main branches of early Prosimians into lemuriforms and lorisiforms occurred in Africa 50 – 80 million years ago. The lemuriform ancestor invaded Madagascar to initiate the highly varied radiation of lemurs (Horvath and Willard, 2007), and lorisiforms divided into lorisides and galagosides (Roos et al., 2004). The galagos, including Otolemur garnetti (formerly Galago garnetti), remained in Africa, whereas one of the two lorisid lineages migrated to Asia. Most of what is known about the organization of Prosimian brains comes from studies of galagos. Previously, several papers have described some aspects of pulvinar connections in galagos (Glendenning et al., 1975; Raczkowski and Diamond, 1978, 1980, 1981; Symonds and Kaas, 1978; Carey et al., 1979; Wall et al., 1982). The present results, together with previous findings, allow a more comprehensive understanding of pulvinar organization in galagos as well as a comparison with what is now known about pulvinar organization in monkeys. The major conclusion stemming from this comparison is that the inferior pulvinar of galagos, and perhaps other Prosimians, has fewer subdivisions than in monkeys, and cortical connections with various visual cortical areas are not as segregated. The cortical areas investigated in the present study include V1 and V2, areas common to most mammals, and MT, an area characteristic of all primates with no obvious homologue in other mammals (Kaas, 2004). In addition, we describe superior colliculus projections to the pulvinar.
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optical imaging of visually evoked responses in Prosimian primates reveals conserved features of the middle temporal visual area
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Xiangmin Xu, Christine E Collins, Jon H. Kaas, Peter M Kaskan, Ilya Khaytin, Vivien A CasagrandeAbstract:Optical imaging of intrinsic cortical responses to visual stimuli was used to characterize the organization of the middle temporal visual area (MT) of a Prosimian primate, the bush baby (Otolemur garnetti). Stimulation with moving gratings revealed a patchwork of oval-like domains in MT. These orientation domains could, in turn, be subdivided into zones selective to directional movements that were mainly orthogonal to the preferred orientation. Similar, but not identical, zones were activated by movements of random dots in the preferred direction. Orientation domains shifted in preference systematically either around a center to form pinwheels or as gradual linear shifts. Stimuli presented in different portions of the visual field demonstrated a global representation of visual space in MT. As optical imaging has revealed similar features in MT of New World monkeys, MT appears to have retained these basic features of organization for at least the 60 million years since the divergence of Prosimian and simian primates.
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topographic patterns of v2 cortical connections in a Prosimian primate galago garnetti
The Journal of Comparative Neurology, 2001Co-Authors: Christine E Collins, Iwona Stepniewska, Jon H. KaasAbstract:: Topographic patterns of cortical connections of the second visual area (V2) were examined in a lorisiform Prosimian primate (Galago garnetti). Up to five different tracers were injected into dorsal and ventral V2. Tracers included wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and up to four fluorochromes. Tracer injections consistently labeled neurons and terminals in primary visual cortex (V1), V2, the middle temporal area (MT), and the dorsolateral visual area (DL). Labeled neurons were also found in other proposed extrastriate areas such as the dorsomedial visual area (DM), dorsointermediate area (DI), middle temporal crescent (MTc), medial superior temporal area (MST), ventral posterior parietal area (VPP), and caudal inferotemporal cortex (ITc), but these connections were more variable and less dependent on the retinotopic position of injection sites in V2. Areal boundaries were identified by differences in cytochrome oxidase (CO) and myelin staining. We conclude that V2 cortical connections in Prosimian galagos are similar to those in simian primates, suggesting that Prosimians and other lines of primate evolution have retained several visual areas from a common ancestor that relate to V2 in similar ways. Architectural features of striate and extrastriate areas in Prosimian galagos are similar to simian primates, with notable exceptions such as stripes in V2, which appear to be less differentiated in galagos.
Vivien A Casagrande - One of the best experts on this subject based on the ideXlab platform.
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optical imaging of visually evoked responses in Prosimian primates reveals conserved features of the middle temporal visual area
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Xiangmin Xu, Christine E Collins, Jon H. Kaas, Peter M Kaskan, Ilya Khaytin, Vivien A CasagrandeAbstract:Optical imaging of intrinsic cortical responses to visual stimuli was used to characterize the organization of the middle temporal visual area (MT) of a Prosimian primate, the bush baby (Otolemur garnetti). Stimulation with moving gratings revealed a patchwork of oval-like domains in MT. These orientation domains could, in turn, be subdivided into zones selective to directional movements that were mainly orthogonal to the preferred orientation. Similar, but not identical, zones were activated by movements of random dots in the preferred direction. Orientation domains shifted in preference systematically either around a center to form pinwheels or as gradual linear shifts. Stimuli presented in different portions of the visual field demonstrated a global representation of visual space in MT. As optical imaging has revealed similar features in MT of New World monkeys, MT appears to have retained these basic features of organization for at least the 60 million years since the divergence of Prosimian and simian primates.
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visual field representation in striate and prestriate cortices of a Prosimian primate galago garnetti
Journal of Neurophysiology, 1997Co-Authors: Marcello G P Rosa, Todd M Preuss, Vivien A Casagrande, Jon H. KaasAbstract:Rosa, Marcello G. P., Vivien A. Casagrande, Todd Preuss, and Jon H. Kaas. Visual field representation in striate and prestriate cortices of a Prosimian primate (Galago garnetti). J. Neurophysiol. 7...
William L Jungers - One of the best experts on this subject based on the ideXlab platform.
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body size and scaling of the hands and feet of Prosimian primates
American Journal of Physical Anthropology, 2007Co-Authors: Pierre Lemelin, William L JungersAbstract:The hands and feet of primates fulfill a variety of biological roles linked with food acquisition and positional behavior. Current explanations of shape differences in cheiridial morphology among Prosimians are closely tied to body size differences. Although numerous studies have examined the relationships between body mass and limb morphology in Prosimians, no scaling analysis has specifically considered hand and foot dimensions and intrinsic proportions. In this study, we present such an analysis for a sample of 270 skeletal specimens distributed over eight Prosimian families. The degree of association between size and shape was assessed using nonparametric correlational techniques, while the relationship between each ray element length and body mass (from published data and a body mass surrogate) was tested for allometric scaling. Since tarsiers and strepsirrhines encompass many taxa of varying degrees of phylogenetic relatedness, effective degrees of freedom were calculated, and comparisons between families were performed to partially address the problem of statistical nonindependence and “phylogenetic inertia.” Correlational analyses indicate negative allometry between relative phalangeal length (as reflected by phalangeal indices) and body mass, except for the pollex and hallux. Thus, as size increases, there is a significant decrease in the relative length of the digits when considering all Prosimian taxa sampled. Regression analyses show that while the digital portion of the rays scales isometrically with body mass, the palmar/plantar portion of the rays often scales with positive allometry. Some but not all of these broadly interspecific allometric patterns remain statistically significant when effective degrees of freedom are taken into account. As is often the case in interspecific scaling, comparisons within families show different scaling trends in the cheiridia than those seen across families (i.e., lorisids, indriids, and lemurids exhibit rather different allometries). The interspecific pattern of positive allometry that appears to best characterize the metapodials of Prosimians, especially those of the foot, parallels differences found in the morphology of the volar skin. Indeed, relatively longer metapodials appear to covary with flatter and more coalesced volar pads, which in turn slightly improve frictional force for animals that are at a comparative disadvantage while climbing because of their larger mass. Despite the essentially isometric relationship found between digit length and body mass across Prosimians, examination of the residual variation reveals that tarsiers and Daubentonia possess, relative to their body sizes, remarkably long fingers. Such marked departures between body size and finger length observed in these particular primates are closely linked with specialized modes of prey acquisition and manipulation involving the hands. Am J Phys Anthropol, 2007. © 2007 Wiley-Liss, Inc.
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long bone cross sectional dimensions locomotor adaptations and body size in Prosimian primates
Journal of Human Evolution, 1993Co-Authors: Brigitte Demes, William L JungersAbstract:The cross-sectional geometry of primate long bones appears to be closely related to body size and locomotor behavior. This study investigates this aspect of skeletal design in the humerus and femur of living Prosimian primates, a group characterized by a diversity of locomotor modes and a wide range of body sizes. The geometrical variables were collected from biplanar radiographs using formulae for hollow ellipses to approximate cortical area, wall thickness, second and polar moments of area, and section modulus. Indices of strength in static compression and bending were also derived from these data, limb length and body mass. For Prosimians as a group, all cross-sectional geometrical properties scale in a positive allometric fashion with body mass (although some of the humeral values have confidence limits that include isometry). Despite positive allometry, measures of strength in static loading decrease as a function of body size and imply that alterations in body posture and locomotion are necessary in order to maintain stress/strain similarity. Within Prosimians, leapers tend to have more robust femora (with elongated anteroposterior axes) than non-saltatory species of the same size; no such distinctions exist for the humerus (but Daubentonia exhibits an unusually strong humerus). Slow climbing lorisines, although exposed to only moderate locomotor forces, are not at the low end of absolute and relative bone strength variation. Prosimians less than 1·2 kg exhibit considerable variation in cross-sectional geometry, a finding that could complicate attempts to use such data to reconstruct body size in small-bodied fossil Prosimians. Measures of wall thickness (K-values) appear to be of limited utility in the functional analysis of skeletal design in extant Prosimians. Compound indices of relative strength—although useful in functional allometric analyses—do not reliably differentiate among either locomotor or taxonomic groups. Functional differences among taxa are more obvious in geometrical properties when body size is used as a covariate.
