Shoulder Muscle Architecture in the Echidna (Monotremata: Tachyglossus aculeatus) Indicates Conserved Functional Properties

Regnault, Sophie; Fahn-Lai, Philip; Norris, Regina D.; Pierce, Stephanie E.

doi:10.1007/s10914-020-09498-6

Cited by 21 publications

(39 citation statements)

References 21 publications

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“…The ability to tune also presents the future opportunity of solving and tuning for specific behaviours one-at-a-time, thereby shedding insight on how muscle–tendon anatomy may need to be adapted for the execution of a specific behaviour, how this may affect the execution of a different behaviour, and how trade-offs may exist for some muscles across disparate behaviours or performance requirements [ 149 , 150 ]. In turn, this tuning approach can provide the foundation to reconciling interspecific differences in muscle architecture (or more generally, musculoskeletal function) in terms of differences in ecology and selective regime [e.g., 151 , 152 , 153 ].…”

Section: Discussionmentioning

confidence: 99%

Computational modelling of muscle fibre operating ranges in the hindlimb of a small ground bird (Eudromia elegans), with implications for modelling locomotion in extinct species

et al. 2021

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The arrangement and physiology of muscle fibres can strongly influence musculoskeletal function and whole-organismal performance. However, experimental investigation of muscle function during in vivo activity is typically limited to relatively few muscles in a given system. Computational models and simulations of the musculoskeletal system can partly overcome these limitations, by exploring the dynamics of muscles, tendons and other tissues in a robust and quantitative fashion. Here, a high-fidelity, 26-degree-of-freedom musculoskeletal model was developed of the hindlimb of a small ground bird, the elegant-crested tinamou (Eudromia elegans, ~550 g), including all the major muscles of the limb (36 actuators per leg). The model was integrated with biplanar fluoroscopy (XROMM) and forceplate data for walking and running, where dynamic optimization was used to estimate muscle excitations and fibre length changes throughout both gaits. Following this, a series of static simulations over the total range of physiological limb postures were performed, to circumscribe the bounds of possible variation in fibre length. During gait, fibre lengths for all muscles remained between 0.5 to 1.21 times optimal fibre length, but operated mostly on the ascending limb and plateau of the active force-length curve, a result that parallels previous experimental findings for birds, humans and other species. However, the ranges of fibre length varied considerably among individual muscles, especially when considered across the total possible range of joint excursion. Net length change of muscle–tendon units was mostly less than optimal fibre length, sometimes markedly so, suggesting that approaches that use muscle–tendon length change to estimate optimal fibre length in extinct species are likely underestimating this important parameter for many muscles. The results of this study clarify and broaden understanding of muscle function in extant animals, and can help refine approaches used to study extinct species.

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Section: Discussionmentioning

confidence: 99%

Computational modelling of muscle fibre operating ranges in the hindlimb of a small ground bird (Eudromia elegans), with implications for modelling locomotion in extinct species

et al. 2021

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“…The echidna had the greatest summed MMAs for humeral pronation (figure 3) as expected based on its reliance on humeral long-axis rotation during propulsion [14,16]. Many of the echidna's individual muscles possessed higher MMAs for pronation than their homologues in the tegu (figure 4), but particularly the m. latissimus dorsi, which has a derived attachment site on the distal humeral entepicondyle [26]. The echidna also possesses muscles absent in the tegu; of these, the m. teres major has a substantial pronation MMA (figure 4).…”

Section: Shoulder Muscle Elevation Leverage Key To Parasagittal Posturementioning

confidence: 59%

“…All specimens used here were digitized as part of previous studies [13,16,26]. Briefly, specimens were contrast stained with Lugol's iodine and micro-CT scanned (for specimen details and scan parameters, see table S1) to capture both hard-and soft-tissue anatomy.…”

Section: Shoulder Musculoskeletal Geometrymentioning

confidence: 99%

“…proximally on the humerus, and the humerus itself is much more gracile [13,26]; this brings the muscle insertion sites closer to the axes of rotation, reducing MMAs but increasing the arc of the limb.…”

Section: Shoulder Muscle Elevation Leverage Key To Parasagittal Posturementioning

confidence: 99%

“…This is also true if we only compare poses which are viable in both taxa (figure S5). Compared to the echidna, many muscles in the tegu insert more proximally on the humerus, and the humerus itself is much more gracile [13,26]; this brings the muscle insertion sites closer to the axes of rotation, reducing MMAs but increasing the arc of the limb.…”

Section: Shoulder Muscle Elevation Leverage Key To Parasagittal Posturementioning

confidence: 99%

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Musculoskeletal modelling of sprawling and parasagittal forelimbs provides insight into synapsid postural transition

Brocklehurst

Fahn-Lai

Regnault

et al. 2021

Preprint

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The sprawling-parasagittal postural shift was a major transition during synapsid evolution and is considered key to mammalian ecological diversity. Despite a good fossil record, debate remains over when the shift to parasagittal posture occurred, primarily due to limited comparative biomechanical data on extant species. Here, we built forelimb musculoskeletal models of three extant taxa that bracket the sprawling-parasagittal transition: a tegu lizard, an echidna, and an opossum. We measured shoulder joint range of motion (ROM) about all three degrees of rotational freedom and characterized shoulder muscle moment arms (MMAs) across the entire pose space. Our results show that both the opossum and the tegu had high shoulder joint ROM, and both were substantially higher than the echidna. However, the opossum occupied a distinct region of pose space characterized by high humeral retraction angles. There are clear interspecific differences in MMAs related to posture, with the sprawling tegu and echidna emphasizing humeral depression, and the parasagittal opossum emphasizing humeral elevation. There are also notable differences between our sprawling taxa, with the echidna possessing much greater moment arms for humeral pronation than the tegu. We demonstrate clear functional variation between locomotor grades and use these data to hypothesize major shifts in forelimb function and posture along the mammalian stem.

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The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb

Bishop,

Pierce

2023

The Anatomical Record

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This paper is the first in a two‐part series that charts the evolution of appendicular musculature along the mammalian stem lineage, drawing upon the exceptional fossil record of extinct synapsids. Here, attention is focused on muscles of the forelimb. Understanding forelimb muscular anatomy in extinct synapsids, and how this changed on the line to mammals, can provide important perspective for interpreting skeletal and functional evolution in this lineage, and how the diversity of forelimb functions in extant mammals arose. This study surveyed the osteological evidence for muscular attachments in extinct mammalian and nonmammalian synapsids, two extinct amniote outgroups, and a large selection of extant mammals, saurians, and salamanders. Observations were integrated into an explicit phylogenetic framework, comprising 73 character–state complexes covering all muscles crossing the shoulder, elbow, and wrist joints. These were coded for 33 operational taxonomic units spanning >330 Ma of tetrapod evolution, and ancestral state reconstruction was used to evaluate the sequence of muscular evolution along the stem lineage from Amniota to Theria. In addition to producing a comprehensive documentation of osteological evidence for muscle attachments in extinct synapsids, this work has clarified homology hypotheses across disparate taxa and helped resolve competing hypotheses of muscular anatomy in extinct species. The evolutionary history of mammalian forelimb musculature was a complex and nonlinear narrative, punctuated by multiple instances of convergence and concentrated phases of anatomical transformation. More broadly, this study highlights the great insight that a fossil‐based perspective can provide for understanding the assembly of novel body plans.

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Shoulder Muscle Architecture in the Echidna (Monotremata: Tachyglossus aculeatus) Indicates Conserved Functional Properties

Cited by 21 publications

References 21 publications

Computational modelling of muscle fibre operating ranges in the hindlimb of a small ground bird (Eudromia elegans), with implications for modelling locomotion in extinct species

Computational modelling of muscle fibre operating ranges in the hindlimb of a small ground bird (Eudromia elegans), with implications for modelling locomotion in extinct species

Musculoskeletal modelling of sprawling and parasagittal forelimbs provides insight into synapsid postural transition

The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb

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