The architectural and functional specifications of intrinsic muscles of the fore limb of the Egyptian Baladi goats (Capra hircus)

Gewaily, Mahmoud S.; Fayed, Masoud Hassan; Farrag, Foad

doi:10.5455/ajvs.280875

Cited by 3 publications

(1 citation statement)

References 28 publications

(43 reference statements)

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“…Based on our understanding of how morphometric features scale with changes in mass (Biewener 2003(Biewener , 2005, the similarities in flexor insertions and lever-arm measurements between the cursorial palaeotheres (20-80kg) and the more massive T. terrestris (~220kg) and T. indicus (~325kg) suggest that muscles acting on the shoulder of cursorial palaeotheres (e.g., Plagiolophus) were disproportionately smaller relative to those of extant tapirs. This means that the muscle mass around the shoulder would have been very limited, giving the shoulder region of smaller cursorial palaeotheres a very gracile appearance akin to small antelopes, chevrotains, and goats (Gewaily et al 2017). Interestingly, juvenile members of T. indicus demonstrate shoulder flexor insertions approximately central to the humeral diaphysis (MacLaren, pers.…”

Section: Cursorial Palaeothere Shoulder Analogymentioning

confidence: 99%

Modern Tapirs as Morphofunctional Analogues for Locomotion in Endemic Eocene European Perissodactyls

Maclaren

Nauwelaerts

2019

J Mammal Evol

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Tapirs have historically been considered as ecologically analogous to several groups of extinct perissodactyls based on dental and locomotor morphology. Here, we investigate comparative functional morphology between living tapirs and endemic Eocene European perissodactyls to ascertain whether tapirs represent viable analogues for locomotion in palaeotheres and lophiodontids.Forelimb bones from 20 species of Eocene European perissodactyls were laser scanned and compared to a forelimb dataset of extant Tapirus. Bone shape was quantified using 3D geometric morphometrics; coordinates were Procrustes aligned and compared using Principal Component Analysis and neighbor-joining trees. Functional traits included lever-arm ratios (LARs; proxy for joint angular velocity), long-bone proportions (speed proxy), and estimated body mass. Results suggest that Paralophiodon and Palaeotherium magnum resemble Neotropical tapirs in humeral morphology and LARs. Palaeotheres demonstrate extensive forelimb shape disparity. Despite previous assessments, metacarpal shape analyzes do not support a strong morphological similarity between palaeotheres and tapirs, with Tapirus pinchaque representing the closest analogue for Eocene European equoid manus morphology. Our analyzes suggest lophiodontids were not capable of moving as swiftly as tapirs due to greater loading over the manus. We conclude that the variation within modern tapir forelimb morphology confounds the assignment of one living analogue within Tapirus for extinct European equoids, whereas tapirs adapted for greater loading over the manus (e.g., T. bairdii, T. indicus) represent viable locomotor analogues for lophiodontids. This study represents a valuable first step toward locomotor simulation and behavioral inference for both hippomorph and tapiromorph perissodactyls in Eocene faunal communities.

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Section: Cursorial Palaeothere Shoulder Analogymentioning

confidence: 99%

Modern Tapirs as Morphofunctional Analogues for Locomotion in Endemic Eocene European Perissodactyls

Maclaren

Nauwelaerts

2019

J Mammal Evol

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From fibre to function: are we accurately representing muscle architecture and performance?

et al. 2022

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The size and arrangement of fibres play a determinate role in the kinetic and energetic performance of muscles. Extrapolations between fibre architecture and performance underpin our understanding of how muscles function and how they are adapted to power specific motions within and across species. Here we provide a synopsis of how this 'fibre to function' paradigm has been applied to understand muscle design, performance and adaptation in animals. Our review highlights the widespread application of the fibre to function paradigm across a diverse breadth of biological disciplines but also reveals a potential and highly prevalent limitation running through past studies. Specifically, we find that quantification of muscle architectural properties is almost universally based on an extremely small number of fibre measurements. Despite the volume of research into muscle properties, across a diverse breadth of research disciplines, the fundamental assumption that a small proportion of fibre measurements can accurately represent the architectural properties of a muscle has never been quantitatively tested. Subsequently, we use a combination of medical imaging, statistical analysis, and physics-based computer simulation to address this issue for the first time. By combining diffusion tensor imaging (DTI) and deterministic fibre tractography we generated a large number of fibre measurements (>3000) rapidly for individual human lower limb muscles. Through statistical subsampling simulations of these measurements, we demonstrate that analysing a small number of fibres (n < 25) typically used in previous studies may lead to extremely large errors in the characterisation of overall muscle architectural properties such as mean fibre length and physiological cross-sectional area. Through dynamic musculoskeletal simulations of human walking and jumping, we demonstrate that recovered errors in fibre architecture characterisation have significant implications for quantitative predictions of in-vivo dynamics and muscle fibre function within a species. Furthermore, by applying data-subsampling simulations to comparisons of muscle function in humans and chimpanzees, we demonstrate that error magnitudes significantly impact both qualitative and quantitative assessment of muscle specialisation, potentially generating highly erroneous conclusions about the absolute and relative adaption of muscles across species and evolutionary transitions. Our findings have profound implications for how a broad diversity of research fields quantify muscle architecture and interpret muscle function.

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Comparative forelimb myology and muscular architecture of a juvenile Malayan tapir (Tapirus indicus)

Maclaren

McHorse

2019

Journal of Anatomy

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The absence of preserved soft tissues in the fossil record is frequently a hindrance for palaeontologists wishing to investigate morphological shifts in key skeletal systems, such as the limbs. Understanding the soft tissue composition of modern species can aid in understanding changes in musculoskeletal features through evolution, including those pertaining to locomotion. Establishing anatomical differences in soft tissues utilising an extant phylogenetic bracket can, in turn, assist in interpreting morphological changes in hard tissues and modelling musculoskeletal movements during evolutionary transitions (e.g. digit reduction in perissodactyls). Perissodactyls (horses, rhinoceroses, tapirs and their relatives) are known to have originated with a four‐toed (tetradactyl) forelimb condition. Equids proceeded to reduce all but their central digit, resulting in monodactyly, whereas tapirs retained the ancestral tetradactyl state. The modern Malayan tapir (Tapirus indicus) has been shown to exhibit fully functional tetradactyly in its forelimb, more so than any other tapir, and represents an ideal case‐study for muscular arrangement and architectural comparison with the highly derived monodactyl Equus. Here, we present the first quantification of muscular architecture of a tetradactyl perissodactyl (T. indicus), and compare it to measurements from modern monodactyl caballine horse (Equus ferus caballus). Each muscle of the tapir forelimb was dissected out from a cadaver and measured for architectural properties: muscle‐tendon unit (MTU) length, MTU mass, muscle mass, pennation angle, and resting fibre length. Comparative parameters [physiological cross‐sectional area (PCSA), muscle volume, and % muscle mass] were then calculated from the raw measurements. In the shoulder region, the infraspinatus of T. indicus exhibits dual origination sites on either side of the deflected scapular spine. Within ungulates, this condition has only been previously reported in suids. Differences in relative contribution to limb muscle mass between T. indicus and Equus highlight forelimb muscles that affect mobility in the lateral and medial digits (e.g. extensor digitorum lateralis). These muscles were likely reduced in equids during their evolutionary transition from tetradactyl forest‐dwellers to monodactyl, open‐habitat specialists. Patterns of PCSA across the forelimb were similar between T. indicus and Equus, with the notable exceptions of the biceps brachii and flexor carpi ulnaris, which were much larger in Equus. The differences observed in PCSA between the tapir and horse forelimb muscles highlight muscles that are essential for maintaining stability in the monodactyl limb while moving at high speeds. This quantitative dataset of muscle architecture in a functionally tetradactyl perissodactyl is a pivotal first step towards reconstructing the locomotor capabilities of extinct, four‐toed ancestors of modern perissodactyls, and providing further insights into the equid locomotor transition.

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The architectural and functional specifications of intrinsic muscles of the fore limb of the Egyptian Baladi goats (Capra hircus)

Cited by 3 publications

References 28 publications

Modern Tapirs as Morphofunctional Analogues for Locomotion in Endemic Eocene European Perissodactyls

Modern Tapirs as Morphofunctional Analogues for Locomotion in Endemic Eocene European Perissodactyls

From fibre to function: are we accurately representing muscle architecture and performance?

Comparative forelimb myology and muscular architecture of a juvenile Malayan tapir (Tapirus indicus)

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