Phylogenetic variation in hind-limb bone scaling of flightless theropods

Paleobiology ◽  
2016 ◽  
Vol 43 (1) ◽  
pp. 129-143 ◽  
Author(s):  
Nicholas R. Chan
Keyword(s):  
Weight Bearing ◽  
Center Of Mass ◽  
Linear Scaling ◽  
Large Species ◽  
Limb Bone ◽  
Limb Bones ◽  
Scaling Relationships ◽  
Taxonomic Groups ◽  
Leg Bones ◽  
Polynomial Regressions

AbstractThe robusticity of the weight-bearing limbs of large terrestrial animals is expected to increase at a more rapid rate than in their smaller relatives. This scaling has been hypothesized to allow large species to maintain stresses in the limb bones that are similar to those seen in smaller ones. Curvilinear scaling has previously been found in mammals and nonavian theropods but has not been demonstrated in birds. In this study, polynomial regressions of leg-bone length and circumference in terrestrial flightless birds were carried out to test for a relationship similar to that seen in nonavian theropods. Flightless birds exhibit curvilinear scaling, with the femora of large taxa becoming thicker relative to length at a greater rate than in smaller taxa. Evidence was found for nonlinear scaling in the leg bones of nonavian theropods. However, unlike in avians, there is also phylogenetic variation between taxonomic groups, with tyrannosaur leg bones in particular scaling differently than other groups. Phylogenetically corrected quadratic regressions and separate analyses of taxonomic groupings found little phylogenetic variation in flightless birds. It is suggested here that the nonlinear scaling seen in avian femora is due to the need to maintain the position of the knee under a more anterior center of mass, thereby restricting femoral length. The femur of nonavian theropods is not so constrained, with greater variability of the linear scaling relationships between clades. Phylogenetic variation in limb-bone scaling may broaden the errors for mass-predictive scaling equations based on limb-bone measurements of nonavian theropods.

scholarly journals Functional Morphology and Morphological Diversification of Hind Limb Cross-Sectional Traits in Mustelid Mammals

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
P Parsi-Pour ◽  
B M Kilbourne
Keyword(s):  
Hind Limb ◽  
Structural Strength ◽  
Aquatic Environments ◽  
Sectional Area ◽  
Cross Sectional ◽  
Phylogenetic Relatedness ◽  
Limb Bone ◽  
Limb Bones ◽  
Section Modulus ◽  
Second Moments

Synopsis Locomotor habits in mammals are strongly tied to limb bones’ lengths, diameters, and proportions. By comparison, fewer studies have examined how limb bone cross-sectional traits relate to locomotor habit. Here, we tested whether climbing, digging, and swimming locomotor habits reflect biomechanically meaningful differences in three cross-sectional traits rendered dimensionless— cross-sectional area (CSA), second moments of area (SMA), and section modulus (MOD)—using femora, tibiae, and fibulae of 28 species of mustelid. CSA and SMA represent resistance to axial compression and bending, respectively, whereas MOD represents structural strength. Given the need to counteract buoyancy in aquatic environments and soil’s high density, we predicted that natatorial and fossorial mustelids have higher values of cross-sectional traits. For all three traits, we found that natatorial mustelids have the highest values, followed by fossorial mustelids, with both of these groups significantly differing from scansorial mustelids. However, phylogenetic relatedness strongly influences diversity in cross-sectional morphology, as locomotor habit strongly correlates with phylogeny. Testing whether hind limb bone cross-sectional traits have evolved adaptively, we fit Ornstein–Uhlenbeck (OU) and Brownian motion (BM) models of trait diversification to cross-sectional traits. The cross-sectional traits of the femur, tibia, and fibula appear to have, respectively, diversified under a multi-rate BM model, a single rate BM model, and a multi-optima OU model. In light of recent studies on mustelid body size and elongation, our findings suggest that the mustelid body plan—and perhaps that of other mammals—is likely the sum of a suite of traits evolving under different models of trait diversification.

Appendix 4. The Hoxne mammalian remains

1956 ◽  
Vol 239 (665) ◽  
pp. 354-356 ◽  
Keyword(s):  
Pollen Analysis ◽  
Cervus Elaphus ◽  
Equus Caballus ◽  
Bone Surface ◽  
Limb Bone ◽  
Limb Bones

The mammalian remains from Hoxne are few in number and variety. Of the fossils which have been collected only a part have been preserved. Most of these are in the collections at Ipswich Museum and are from Moir’s (1926, 1935) excavations, and these are listed below. The stratigraphical horizon is given where known. Trogontherium sp. Femur and eight molars from stratum E. Provisionally determined by Dr T. M. Stout as T. lydekkeri Schlosser. Cervus elaphus L. Limb bones, antler fragments and a vertebra. These remains represent at least six animals. A radius and a metacarpal were found together in stratum F lying on the Lowestoft Till; these were the only finds during the recent investigations. Their position in the stratigraphy was verified by pollen analysis (no. 10, table 5) of sediment from the bone surface. Bos or Bison sp. Tooth and a limb bone. Equus caballus L. Teeth and limb bones. These belong to at least eight beasts. Several of the teeth are known to have come from stratum A 2. Elephas sp. Ilium.

scholarly journals Correlated evolution of neck length and leg length in birds

2019 ◽  
Vol 6 (5) ◽  
pp. 181588 ◽  
Author(s):  
Christine Böhmer ◽  
Olivia Plateau ◽  
Raphäel Cornette ◽  
Anick Abourachid
Keyword(s):  
Body Size ◽  
Vertebral Column ◽  
High Variability ◽  
Large Species ◽  
Leg Length ◽  
Neck Length ◽  
Correlated Evolution ◽  
Scaling Relationships ◽  
Extant Species ◽  
Total Leg

Despite a diversity of about 10 000 extant species, the sophisticated avian ‘body plan’ has not much changed once it was achieved around 160 Ma after the origin of powered flight. All birds are bipedal having wings, a rigid trunk, a short and ossified tail, a three-segmented leg and digitigrade feet. The avian neck, however, has always been regarded as a classic example of high variability ranging from short necks in songbirds to extremely long, serpentine necks in herons. Yet, the wide array of small to very large species makes it difficult to evaluate the actual neck length. Here, we investigate the evolution of the vertebral formulae in the neck of birds and the scaling relationships between skeletal dimensions and body size. Cervical count in birds is strongly related to phylogeny, with only some specialists having an exceptional number of vertebrae in the neck. In contrast with mammals, the length of the cervical vertebral column increases as body size increases and, thus, body size does not constrain neck length in birds. Indeed, neck length scales isometrically with total leg length suggesting a correlated evolution between both modules. The strong integration between the cervical and pelvic module in birds is in contrast with the decoupling of the fore- and hindlimb module and may be the result of the loss of a functionally versatile forelimb due to the evolution of powered flight.

scholarly journals Biomechanical Control of Paretic Lower Limb During Imposed Weight Transfer in Individuals Post-Stroke

2020 ◽  
Author(s):  
Hao-Yuan Hsiao ◽  
Vicki L Gray ◽  
James Borrelli ◽  
Mark W Rogers
Keyword(s):  
Lower Limb ◽  
Center Of Pressure ◽  
Weight Bearing ◽  
Center Of Mass ◽  
Step Test ◽  
Control Group ◽  
Post Stroke ◽  
Paretic Limb ◽  
Four Square ◽  
Weight Transfer

Abstract Background: stroke is a leading cause of disability with associated hemiparesis resulting in difficulty bearing and transferring weight on to the paretic limb. Difficulties in weight bearing and weight transfer may result in impaired mobility and balance, increased fall risk, and decreased community engagement. Despite considerable efforts aimed at improving weight transfer after stroke, impairments in its neuromotor and biomechanical control remain poorly understood. In the present study, a novel experimental paradigm was used to characterize differences in weight transfer biomechanics in individuals with chronic stroke versus able-bodied controls. Methods: fifteen participants with stroke and fifteen age-matched able-bodied controls participated in the study. Participants stood with one foot on each of two custom built platforms. One of the platforms dropped 4.3 cm vertically to induce lateral weight transfer and weight bearing. Paretic lower extremity joint kinematics, vertical ground reaction forces, and center of pressure velocity were measured. All participants completed the clinical Step Test and Four-Square Step Test. Results: reduced paretic ankle, knee, and hip joint angular displacement and velocity, delayed ankle and knee inter-joint timing, and altered center of pressure (COP) and center of mass control were exhibited in the stroke group compared to the control group. In addition, paretic COP velocity stabilization time during induced weight transfer predicted Four-Square Step Test scores in individuals post-stroke. Conclusions: the induced weight transfer approach identified stroke-related abnormalities in the control of weight transfer towards the paretic limb side compared to controls. Decreased joint flexion of the paretic ankle and knee, altered inter-joint timing, and altered COP and center of mass control appear to limit rapid lower limb loading ability. Future work will investigate the potential of improving functional weight transfer through induced weight transfer training exercise.

Activity-Based Screening of Homogeneous Catalysts through the Rapid Assessment of Theoretically Derived Turnover Frequencies

2019 ◽  
Author(s):  
Matthew Wodrich ◽  
Boodsarin Sawatlon ◽  
Ephrath Solel ◽  
sebastian kozuch ◽  
Clemence Corminboeuf
Keyword(s):  
Free Energy ◽  
Rapid Assessment ◽  
Linear Scaling ◽  
Computational Studies ◽  
Turnover Frequency ◽  
Turnover Number ◽  
Pincer Ligand ◽  
Scaling Relationships ◽  
Energy Profiles ◽  
Hydrogenation Of Co

In homogeneous catalysis, the turnover frequency (TOF) and turnover number (TON) are the most commonly used quantities that experimentally describe catalytic activity. Computational studies, on the other hand, generally yield the ubiquitous free energy profile, which only provides the relative heights of different intermediates and transition states for a given reaction mechanism. This information, however, can be converted into a theoretical TOF through use of the energy span model. Clearly, directly computing turnover frequencies not only allows easy comparison of the activity of different catalysts, but also provides a means of directly comparing theory and experiment. Nonetheless, obtaining detailed free energy profiles for many catalysts is computationally costly. To overcome this and accelerate the rate at which prospective catalysts can be screened, here we use linear scaling relationships in tandem with the energy span model to create volcano plots that relate an easily and quickly computed energetic descriptor variable with a catalyst’s turnover frequency. As a demonstration of their ability, we use these “TOF volcanoes” to rapidly screen prospective transition metal/pincer-ligand catalysts based on activity in facilitating the hydrogenation of CO<sub>2</sub>to formate.

The Differential Growth Response of Embryonic Chick Limb-bone Rudiments to Triiodothyronine in vitro

Development ◽  
1961 ◽  
Vol 9 (1) ◽  
pp. 42-51
Author(s):  
Kirstie Lawson
Keyword(s):  
Vitamin A ◽  
Thyroid Hormones ◽  
Growth Response ◽  
Nutritional Deficiencies ◽  
Embryonic Chick ◽  
Differential Growth ◽  
Relative Growth ◽  
Limb Bone ◽  
Leg Bones

The proportionate development of the embryonic chick skeleton can be influenced experimentally by a variety of factors such as nutritional deficiencies (Byerly, Titus, Ellis, & Landauer, 1935; Landauer, 1936; Romanoff & Bauernfeind, 1942; Couch, Cravens, Elvehjem, & Halpin, 1948), teratogens (Ancel & Lallemand, 1942; Zwilling & de Bell, 1950; Landauer, 1952, 1953a, 1954) and excess hormones (Willier, 1924; Landauer & Bliss, 1946; Duraiswami, 1950). The leg bones are generally more severely affected than the wing bones, but a comparison of the action of several teratogens on the character of the malformations and on the relative growth of the leg bones indicated that the response of individual bones varies with the different agents (Landauer & Rhodes, 1952; Landauer, 1953 a, b, 1954). Cartilaginous limb-bone rudiments also respond differentially when they are isolated from the embryo and exposed in culture to various compounds, such as insulin (Chen, 1954), vitamin A, and the thyroid hormones (Fell & Mellanby, 1955, 1956).

scholarly journals Limb bone loading in swimming turtles: changes in loading facilitate transitions from tubular to flipper-shaped limbs during aquatic invasions

2015 ◽  
Vol 11 (6) ◽  
pp. 20150110 ◽  
Author(s):  
Vanessa K Hilliard Young ◽  
Richard W. Blob
Keyword(s):  
Cross Sections ◽  
Morphological Changes ◽  
Skeletal Morphology ◽  
Limb Bone ◽  
Limb Bones ◽  
Terrestrial Vertebrate ◽  
Aquatic Invasions ◽  
Torsional Loads ◽  
The Impact

Members of several terrestrial vertebrate lineages have returned to nearly exclusive use of aquatic habitats. These transitions were often accompanied by changes in skeletal morphology, such as flattening of limb bone shafts. Such morphological changes might be correlated with the exposure of limb bones to altered loading. Though the environmental forces acting on the skeleton differ substantially between water and land, no empirical data exist to quantify the impact of such differences on the skeleton, either in terms of load magnitude or regime. To test how locomotor loads change between water and land, we compared in vivo strains from femora of turtles ( Trachemys scripta ) during swimming and terrestrial walking. As expected, strain magnitudes were much lower (by 67.9%) during swimming than during walking. However, the loading regime of the femur also changed between environments: torsional strains are high during walking, but torsion is largely eliminated during swimming. Changes in loading regime between environments may have enabled evolutionary shifts to hydrodynamically advantageous flattened limb bones in highly aquatic species. Although circular cross sections are optimal for resisting torsional loads, the removal of torsion would reduce the advantage of tubular shapes, facilitating the evolution of flattened limbs.

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