Hypaxial Motor Patterns and the Function of Epipubic Bones in Primitive Mammals

Reilly, Steve; White, Thomas D.

doi:10.1126/science.1074905

Cited by 33 publications

(29 citation statements)

References 16 publications

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“…As this study shows, as well as previous investigations, sagittal bending is more widespread among eutherian and also metatherian mammals (Pridmore, 1992;Schilling and Fischer, 1999) (this study). This is clearly in contrast to Reilly and White (Reilly and White, 2003), who argued that some metatherians, including the gray short-tailed opossum studied herein, do not exhibit asymmetrical gaits because of their epipubic bones which are part of a kinetic linkage. This cross-couplet kinetic connection between the hindlimb and the abdominal body wall is presumed to restrict the animals to symmetrical gaits (Reilly and White, 2003).…”

Section: The Journal Of Experimental Biologycontrasting

confidence: 51%

“…This is clearly in contrast to Reilly and White (Reilly and White, 2003), who argued that some metatherians, including the gray short-tailed opossum studied herein, do not exhibit asymmetrical gaits because of their epipubic bones which are part of a kinetic linkage. This cross-couplet kinetic connection between the hindlimb and the abdominal body wall is presumed to restrict the animals to symmetrical gaits (Reilly and White, 2003). But the use of asymmetrical gaits in the gray short-tailed opossum has been reported earlier and its locomotor parameters have been analyzed quantitatively (Pridmore, 1992;Kühnapfel, 1996;Fischer et al, 2002).…”

Section: The Journal Of Experimental Biologycontrasting

confidence: 51%

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Sagittal spine movements of small therian mammals during asymmetrical gaits

Schilling

Hackert

2006

Journal of Experimental Biology

112

111

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SUMMARY Mammalian locomotion is characterized by the use of asymmetrical gaits associated with extensive flexions and extensions of the body axis. Although the impact of sagittal spine movements on locomotion is well known, little information is available on the kinematics of spinal motion. Intervertebral joint movements were studied in two metatherian and three eutherian species during the gallop and halfbound using high-speed cineradiography. Fast-Fourier transformation was used to filter out high frequency digitizing errors and keep the lower frequency sinusoid oscillations that characterize the intervertebral angular movements. Independent of their regional classification as thoracic or lumbar vertebrae, 7±1 presacral intervertebral joints were involved in sagittal bending movements. In only one species, no more than five intervertebral joints contributed to the resulting `pelvic movement'. In general, the trunk region involved in sagittal bending during locomotion did not correspond to the traditional subdivisions of the vertebral column (e.g. as thoracic and lumbar or pre- and postdiaphragmatic region). Therefore, these classifications do not predict the regions involved in spinal oscillations during locomotion. Independent of the gait, maximum flexion of the spine was observed in the interval between the last third of the swing phase and touch-down. This results in a retraction of the pelvis and hindlimbs before touch-down and, we hypothesize, enhances the stability of the system. Maximum extension occurred during the first third of the swing phase (i.e. after lift-off) in all species. In general, the observed timing of dorsoventral oscillations of the spine are in accordance with that observed in other mammals and with activity data of respiratory and epaxial back muscles. Although no strict craniocaudal pattern was observable, the more cranial intervertebral joints tend to flex and extend earlier than the more caudal ones. This is in accordance with the organization and the activation of the paravertebral musculature in mammals. The amplitude of intervertebral joint movements increased caudally, reaching its highest values in the presacral joint. The more intense sagittal bending movements in the caudal intervertebral joints are reflected by the muscle fiber type composition of the back muscles involved. Despite the highly similar amplitude of `pelvic motion', touch-down and lift-off positions of the pelvis were clearly different between the species with a long, external tail and those with no external tail.

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Section: The Journal Of Experimental Biologycontrasting

confidence: 51%

Section: The Journal Of Experimental Biologycontrasting

confidence: 51%

Sagittal spine movements of small therian mammals during asymmetrical gaits

Schilling

Hackert

2006

Journal of Experimental Biology

112

111

View full text Add to dashboard Cite

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“…Many paleontologists have considered epipubic bones as evidence that mammaliaforms and early mammals (including early eutherians) carried eggs or young in a pouch or suspended from the abdomen; however, others argue that epipubic bones rather had a function in locomotion as the structure of the pelvis evolved (Novacek et al, 1997;Reilly and White, 2003). Pouches have evolved in both monotremes (e.g.…”

Section: Milk Secretion In the Context Of Synapsid Evolutionmentioning

confidence: 99%

The evolution of milk secretion and its ancient origins

Oftedal

2012

Animal

198

142

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Lactation represents an important element of the life history strategies of all mammals, whether monotreme, marsupial, or eutherian. Milk originated as a glandular skin secretion in synapsids (the lineage ancestral to mammals), perhaps as early as the Pennsylvanian period, that is, approximately 310 million years ago (mya). Early synapsids laid eggs with parchment-like shells intolerant of desiccation and apparently dependent on glandular skin secretions for moisture. Mammary glands probably evolved from apocrine-like glands that combined multiple modes of secretion and developed in association with hair follicles. Comparative analyses of the evolutionary origin of milk constituents support a scenario in which these secretions evolved into a nutrient-rich milk long before mammals arose. A variety of antimicrobial and secretory constituents were co-opted into novel roles related to nutrition of the young. Secretory calcium-binding phosphoproteins may originally have had a role in calcium delivery to eggs; however, by evolving into large, complex casein micelles, they took on an important role in transport of amino acids, calcium and phosphorus. Several proteins involved in immunity, including an ancestral butyrophilin and xanthine oxidoreductase, were incorporated into a novel membrane-bound lipid droplet (the milk fat globule) that became a primary mode of energy transfer. An ancestral c-lysozyme lost its lytic functions in favor of a role as a-lactalbumin, which modifies a galactosyltransferase to recognize glucose as an acceptor, leading to the synthesis of novel milk sugars, of which free oligosaccharides may have predated free lactose. An ancestral lipocalin and an ancestral whey acidic protein four-disulphide core protein apparently lost their original transport and antimicrobial functions when they became the whey proteins b-lactoglobulin and whey acidic protein, which with a-lactalbumin provide limiting sulfur amino acids to the young. By the late Triassic period (ca 210 mya), mammaliaforms (mammalian ancestors) were endothermic (requiring fluid to replace incubatory water losses of eggs), very small in size (making large eggs impossible), and had rapid growth and limited tooth replacement (indicating delayed onset of feeding and reliance on milk). Thus, milk had already supplanted egg yolk as the primary nutrient source, and by the Jurassic period (ca 170 mya) vitellogenin genes were being lost. All primary milk constituents evolved before the appearance of mammals, and some constituents may have origins that predate the split of the synapsids from sauropsids (the lineage leading to 'reptiles' and birds). Thus, the modern dairy industry is built upon a very old foundation, the cornerstones of which were laid even before dinosaurs ruled the earth in the Jurassic and Cretaceous periods.Keywords: evolution, lactation, milk composition, casein, milk fat globule ImplicationsLactation has an evolutionary origin and biological context within which its secretory processes and milk constituents evolved. This revi...

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“…For example, unlike many mammalian species in which limb bone safety factors have been measured [e.g. horses Biewener et al, 1988)], opossums are constrained to trotting, rather than transitioning to a gallop, as they run at higher speeds (Peters et al, 1984;White, 1990;Reilly and White, 2003). Yet, the question remains why high limb bone safety factors might be maintained in opossums despite the potentially lower demands that they face .…”

Section: Safety Factors In Opossum Femora: Mechanical Basis and Evolumentioning

confidence: 99%

Femoral loading mechanics in the Virginia opossum,Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion

Gosnell

Butcher

Maie

et al. 2011

Journal of Experimental Biology

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SUMMARYStudies of limb bone loading in terrestrial mammals have typically found anteroposterior bending to be the primary loading regime, with torsion contributing minimally. However, previous studies have focused on large, cursorial eutherian species in which the limbs are held essentially upright. Recent in vivo strain data from the Virginia opossum (Didelphis virginiana), a marsupial that uses a crouched rather than an upright limb posture, have indicated that its femur experiences appreciable torsion during locomotion as well as strong mediolateral bending. The elevated femoral torsion and strong mediolateral bending observed in D. virginiana might result from external forces such as a medial inclination of the ground reaction force (GRF), internal forces deriving from a crouched limb posture, or a combination of these factors. To evaluate the mechanism underlying the loading regime of opossum femora, we filmed D. virginiana running over a force platform, allowing us to measure the magnitude of the GRF and its three-dimensional orientation relative to the limb, facilitating estimates of limb bone stresses. This three-dimensional analysis also allows evaluations of muscular forces, particularly those of hip adductor muscles, in the appropriate anatomical plane to a greater degree than previous two-dimensional analyses. At peak GRF and stress magnitudes, the GRF is oriented nearly vertically, inducing a strong abductor moment at the hip that is countered by adductor muscles on the medial aspect of the femur that place this surface in compression and induce mediolateral bending, corroborating and explaining loading patterns that were identified in strain analyses. The crouched orientation of the femur during stance in opossums also contributes to levels of femoral torsion as high as those seen in many reptilian taxa. Femoral safety factors were as high as those of non-avian reptiles and greater than those of upright, cursorial mammals, primarily because the load magnitudes experienced by opossums are lower than those of most mammals. Thus, the evolutionary transition from crouched to upright posture in mammalian ancestors may have been accompanied by an increase in limb bone load magnitudes.

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Hypaxial Motor Patterns and the Function of Epipubic Bones in Primitive Mammals

Cited by 33 publications

References 16 publications

Sagittal spine movements of small therian mammals during asymmetrical gaits

Sagittal spine movements of small therian mammals during asymmetrical gaits

The evolution of milk secretion and its ancient origins

Femoral loading mechanics in the Virginia opossum,Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion

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