Evolutionary Biomechanics

Archaeopteryx lithographica, a pivotal species in the evolutionary link between non-avian dinosaurs and birds, has long intrigued paleontologists due to its unique morphological and ecological features. Fossils from the Solnhofen region in Bavaria, dated to the Late Jurassic (~150 MYA), reveal exceptional preservation conditions that highlight its transitional characteristics. Exhibiting both primitive and derived traits, Archaeopteryx provides evidence of early avian adaptations, including asymmetrical feathers for limited flight or gliding. Its morphology supports the "trees-down" model of flight evolution, with adaptations such as airfoil-like wings and elongated hindlimb feathers serving thermoregulation, display, and stabilization purposes. Despite its significance, debates persist, particularly regarding its phylogenetic relationship with theropod dinosaurs, as exemplified by critiques of theropod origin theories. Continued research on Archaeopteryx lithographica advances our understanding of avian evolution, offering crucial insights into the origins of flight and the morphological innovations shaping bird evolution.

Pelvic evolution from non-avian to avian dinosaurs (modern birds) is often assessed biomechanically, with functions ranging from weight-carrying, ventilation, and locomotion/flight. Recently, reproduction has been hypothesized to have constrained and shaped pelvic morphology along this lineage. Opening of the pelvis by separating the pubes is thought to have allowed an increase in relative egg size and changes in the egg shape. Since reproductive ability would be advantageous for females, pelvic dimorphism may have evolved in this group. Pelvic dimorphism and its correlation with reproduction in non-avian reptiles and mammals have been extensively studied, but not in modern birds. We are currently investigating pelvic size dimorphism using a multiple regression on representative species from the major group of modern birds (n=30). This will test if there is a significant difference in pelvis dimensions between sexes after accounting for body size. We will also use phylogenetic regre...

The paper deals with the torques of external muscles acting on the upper ankle joint under weightbearing conditions and their importance in diagnosing and treating the human foot. Experimental data were collected and calculations were performed. Based on the experiments with the biomechanical model of the foot and upper ankle joint, it was shown how the changes in the force arms of the external muscles of the foot under weight-bearing conditions, change the torque. The real values of muscle forces and torques of the external muscles of the foot were calculated. Taking into account the distance of the lines of muscle action from the axis of rotation of the upper ankle joint the rotational force of the muscles was calculated. The influence of changing the force arm on the rotational efficiency of the muscle balancing the moment of gravity was shown. Knowledge of muscle torque under weight-bearing conditions is crucial for correctly assessing foot biomechanics. It has been shown that torque (gravitational and muscular), not pure force, is crucial when assessing the rotational capacity of the analyzed joint. A change in the approach to diagnostics and treating paresis or weakness of extrinsic foot muscles was proposed through the manipulation of the distance of their action line from the axis of joint rotation.

The extensor tendons of the foot are crucial for maintaining the intricate movements and stability of the foot and ankle complex. Understanding these variations is essential for health-care professionals involved in foot-related pathologies. Aims and Objective: The study was conducted to identify and document variations in extensor tendons of the foot during routine dissection of human cadavers and to highlight their clinical significance. Materials and Methods: This was an observational study conducted in the

Although the knowledges on morphological changes in cattle pelvic symphysis during gestation and obstetrics gives valuable information about the age of optimal primary calving of cows, up to now little research has been carried out about the ossification of pelvic symphysis. The aim of the study was to carry out histochemical and immunohistochemical comparative investigation of pelvic symphysis in calves, in-calfed and after-calved Estonian Holstein-Friesian's (EHF) cattle. The material from the cranial part of the pubic bone, pubo-ischiadic junction, symphyseal eminence and the body of the interischiadic bone was taken for immunohistochemical investigation from eight EHF cows divided into three age groups: calves, in-calfed and after-calved EHF's. Specimen were fixed with 10% formalin, demineralized thereafter in EDTA and embedded into paraffin, slices 7 μm in thickness were cut followed by histochemical staining by Safranin-O and immunohistochemical staining by primary antibodies Collagen-II and Periostin (Novus Biologicals, Littleton, CO, USA). Immunohistochemical staining was carried out according to the manufacturers quidleines (Invitrogen, Carlsbad, CA, USA). Our investigations proved that the main morphological changes, the retardation of ossification processes, in the pelvic symphysis occur in adult EHF kines during the second-half of gestation in the pubo-ischiadic junction.

Microraptor gui, a four-winged dromaeosaur from the Early Cretaceous of China, provides strong evidence for an arboreal-gliding origin of avian flight. It possessed asymmetric flight feathers not only on the manus but also on the pes. A previously published reconstruction shows that the hindwing of Microraptor supported by a laterally extended leg would have formed a second pair of wings in tetrapteryx fashion. However, this wing design conflicts with known theropod limb joints that entail a parasagittal posture of the hindlimb. Here, we offer an alternative planform of the hindwing of Microraptor that is concordant with its feather orientation for producing lift and normal theropod hindlimb posture. In this reconstruction, the wings of Microraptor could have resembled a staggered biplane configuration during flight, where the forewing formed the dorsal wing and the metatarsal wing formed the ventral one. The contour feathers on the tibia were positioned posteriorly, oriented in a vertical plane for streamlining that would reduce the drag considerably. Leg feathers are present in many fossil dromaeosaurs, early birds, and living raptors, and they play an important role in flight during catching and carrying prey. A computer simulation of the flight performance of Microraptor suggests that its biplane wings were adapted for undulatory ''phugoid'' gliding between trees, where the horizontal feathered tail offered additional lift and stability and controlled pitch. Like the Wright 1903 Flyer, Microraptor, a gliding relative of early birds, took to the air with two sets of wings.

Horses and elephants have extreme foot designs; horses have an unguligrade foot posture with small, single-toed, rigid hooves housing a small fibrous digital cushion, whereas elephants have large, multi-toed, functionally plantigrade, compliant feet with large adipose filled digital cushions. The morphology of the digital cushion is divergent in these species, in terms of its size, shape, volume, composition and organisation. In the context of foot-ground contact this is interesting, because feet nonetheless have to perform similar mechanical functions in all terrestrial species. How well the digital cushion functions under load may contribute to the aetiopathogenesis of foot disease; a sub-optimal digital cushion is less likely to distribute (and thus reduce) high pressures, moderate impact shock and vibration, or prevent unwarranted bone displacement. In this study, we seek to understand how the digital cushion morphologies evident in horse and elephant feet influence internal and...

Modularity is considered a prerequisite for the evolvability of biological systems. This is because in theory, individual modules can follow quasi-independent evolutionary trajectories or evolve at different rates compared to other aspects of the organism. This may influence the potential of some modules to diverge, leading to differences in disparity. Here, we investigated this relationship between modularity, rates of morphological evolution and disparity using a phylogenetically diverse sample of ray-finned fishes. We compared the support for multiple hypotheses of evolutionary modularity and asked if the partitions delimited by the best-fitting models were also characterized by the highest evolutionary rate differentials. We found that an evolutionary module incorporating the dorsal, anal and paired fins was well supported by the data, and that this module evolves more rapidly and consequently generates more disparity than other modules. This suggests that modularity may indeed ...

Although several recent studies have described a vast mimicry complex among New World mutillid wasps (velvet ants), little is known about the potential predators that could be driving the colour convergence in these wasps. Identifying potential predators can be a necessary part of understanding the evolution of large mimicry complexes because predation pressures likely are a key evolutionary driver of aposematism in these systems. However, pinpointing potential predators is difficult given the rarity of observing predation events in the wild. Furthermore, laboratory-based feeding trials are difficult to design without a priori information about which potential predators should be investigated. In the present study, we explore the potential predator communities that may have driven the evolution of the large North American velvet ant mimicry complex. We hypothesize that potential predators can be identified by examining: (1) distributional similarities between predators and prey; (2) similarities of predator assemblages in areas where convergently coloured prey occur; (3) known dietary preferences of potential predators; and (4) evolutionary concordance (both spatially and temporally) of predator and prey clades. We find that iguanians are likely predators of two of the described mutillid mimicry rings. We hypothesize that the warning coloration of the Black-headed Timulla and Tropical mimicry rings is particularly directed towards dactyloids (anoles).

Bipedal locomotion evolved along the archosaurian lineage to birds, shifting from "hip-based" to "knee-based" mechanisms. However, the roles of individual muscles in these changes and their evolutionary timings remain obscure. Using 13 three-dimensional musculoskeletal models of the hindlimbs of bird-line archosaurs, we quantify how the moment arms (i.e., leverages) of 35 locomotor muscles evolved. Our results support two hypotheses: From early theropod dinosaurs to birds, knee flexors' moment arms decreased relative to knee extensors', and medial long-axis rotator moment arms for the hip increased (trading off with decreased hip abductor moment arms). Our results reveal how, from the Triassic Period, bipedal theropod dinosaurs gradually modified their hindlimb form and function, shifting more from hip-based to knee-based locomotion and hip-abductor to hip-rotator balancing mechanisms inherited by birds. Yet, we also discover unexpected ancestral specializations in larger Jurassic theropods, lost later in the bird-line, complicating the paradigm of gradual transformation.

Scale effects on whole limb morphology (i.e. bones together with in situ overlying muscles) are well understood for the neognath forelimb. However, scale effects on neognath gross hindlimb morphology remain largely unexplored. To broaden our understanding of avian whole limb morphology, I investigated the scaling of hindlimb inertial properties in neognath birds, testing empirical scaling relationships against the model of geometric similarity. Inertial property data-mass, moment of inertia, centre of mass distance, and radius of gyration-were collected from 22 neognath species representing a wide range of locomotor specializations. When scaled against body mass, hindlimb inertial properties scale with positive allometry. Thus, in terms of morphology, larger bodied neognaths possess hindlimbs requiring disproportionately more energy to accelerate and decelerate relative to body mass than smaller bodied birds. When scaled against limb length, hindlimb inertial properties scale according to isometry. In the subclade Land Birds (sensu Hackett et al.), hindlimb inertial properties largely scale according to positive allometry. The contrasting results of positive allometry vs. isometry in neognaths are due to how hindlimb length scales against body mass. Negative allometry of hindlimb inertial properties, which would reduce terrestrial locomotion costs, would probably make the hindlimb susceptible to mechanical failure or too diminutive for its many ecological functions. Comparing the scaling relationships of wings and hindlimbs highlights how locomotor costs influence the scaling of limb inertial properties.

This slide presentation paper contains compilation of certain tutorial slides prepared by the author as to respond to the members' questions regarding our Ascension and especially how it is accomplished, with a particular reference of the role that the Aurora Beings play in all this.

Mechanisms of aerial righting in juvenile Chukar Partridge (Alectoris chukar) were studied from hatching through 14 days-post-hatching (dph). Asymmetric movements of the wings were used from 1?8 dph to effect progressively more successful righting behaviour via body roll. Following 8 dph, wing motions transitioned to bilaterally symmetric flapping that yielded aerial righting via nose-down pitch, along with substantial increases in vertical force production during descent. Ontogenetically, the use of such wing motions to effect aerial righting precedes both symmetric flapping and a previously documented behaviour in chukar (i.e., wing-assisted incline running) hypothesized to be relevant to incipient flight evolution in birds. These findings highlight the importance of asymmetric wing activation and controlled aerial manoeuvres during bird development, and are potentially relevant to understanding the origins of avian flight.

Even though specialty literature includes a series of publications regarding the muscles of pelvic limb of the African ostrich, there are still a couple of aspects that aren’t entirely understood. Therefore, a series of differences in regards to the insertions of the pectineus muscle and ambiens muscle can be described, as well as the usage of different terminology for the identification of the cranial muscles of the thigh. This study, conducted on 10 african ostriches of different ages and sexes, realized through classic methods and macroscopic investigations, aims to conduct a detailed anatomization of pelvic muscles, more precisely of the muscles whose topography is adjacent to the pelvic region. The nomenclature used was in concordance with the Nomina Anatomica Avium 1993, although this study also suggests other naming options, which from our point of view better reflect the morphological and topographical realities.

The equine radius is a useful subject for examining the adaptation of bone histology to loading because in life the anterior cortex is loaded almost entirely in tension, the posterior cortex in compression. The histology of the two cortices is correspondingly different, the osteones and the interstitial lamellae in the posterior cortex having a more transversely oriented fibre arrangement than those in the anterior cortex. Presumably as a result of this histological difference, the posterior cortex is stronger in compression than the anterior cortex; the anterior cortex is stronger in tension than the posterior cortex. We here use nanoindentation to examine how the Young’s modulus of elasticity of secondary osteones and interstitial lamellae in the anterior and posterior cortices varied as a function of angle. The anterior osteones were stiffer than the posterior osteones when tested in the direction parallel to the bone’s long axis, but became progressively relatively less stiff as...

The Guinea fowl (Numida meleagridis) is a semi-domestic bird whose commercial popularity is on the increase. The gross anatomy of the hindlimbs of 8 helmeted Guinea fowls of equal sexes were studied. The pubic shafts were free, thus they did not fuse ventrally to form a symphysis. The ilium had a quadrilateral and roughly triangular pre and post acetabular wings, respectively. A conspicuous renal fossa was observed in the post acetabular wing. An incomplete concentric obturator foramen, lacking a caudal margin, was formed by the ventral border of the ischium and dorsal border of the cranial pubic shaft, while a prominent ischiopubic fissure was formed by the same bones, caudally. The incomplete concentric nature of the obturator foramen created a common space between it and the ischiopubic fissure. The femoral major trochanter was more proximal than the head, while the minor trochanter and the head were on the same horizontal level. The femur lacked a visible pneumatic foramen. The tibiotarsus had a prominent cranial cnemial crest. The fibular spine terminated at the tibia mid-shaft, leaving one interosseous space. An intertarsal sesamoid bone was identified, indicative of an adult skeleton. Crests and channels depicted the hypotarsus. Vascular foramen was identified in the distal extremity of the tibiotarsus. Digit I was oriented to the planter direction.

Since the 19th century, identification of muscle attachment sites on bones has been important for muscle reconstructions, especially in fossil tetrapods, and therefore has been the subject of numerous biological and paleontological studies. At the microscopic level, in histological thin sections, the only features that can be used reliably for identifying tendon–bone or muscle–tendon‐bone interactions are Sharpey's fibers. Muscles, however, do not only attach to the bone indirectly with tendons, but also directly. Previous studies failed to provide new indicators for muscle attachment, or to address the question of whether muscles with direct attachment can be identified histologically. However, histological identification of direct muscle attachments is important because these attachments do not leave visible marks (e.g. scars and rugosities) on the bone surface. We dissected the right hind limb and mapped the muscle attachment sites on the femur of one rabbit (Oryctolagus cuni...

The current study investigates the effect of altering the point of force application (PFA) from the rearfoot towards the fore of the foot on the metabolic energy consumption and the influence of transitioning to this technique over a short or a longer timeframe. The participants were randomly assigned into two experimental and one control group: a short-term intervention group (STI, N=17; two training sessions), a long-term intervention group (LTI, N=10; 14-week gradual transition) and a control group (CG, N=11). Data were collected at two running velocities (2.5 and 3.0 m s −1). The cost coefficient (i.e. energy required per unit of vertical ground reaction force; J N −1) decreased (P<0.001) after both interventions due to a more anterior PFA during running (STI: 12%, LTI: 11%), but led to a higher (P<0.001) rate of force generation (STI: 17%, LTI: 15.2%). Dynamic stability of running showed a significant (P<0.001) decrease in the STI (2.1%), but no differences (P=0.673) in the LTI. The rate of metabolic energy consumption increased in the STI (P=0.038), but remained unchanged in the LTI (P=0.660). The CG had no changes. These results demonstrate that the cost coefficient was successfully decreased following an alteration in the running technique towards a more anterior PFA. However, the energy consumption remained unchanged because of a simultaneous increase in rate of force generation due to a decreased contact time per step. The increased instability found during the short-term intervention and its neutralization after the long-term intervention indicates a role of motor control errors in the economy of running after acute alterations in habitual running execution.

The respiratory turbinates of mammals are complex bony plates within the nasal chamber that are covered with moist epithelium and provide an extensive surface area for the exchange of heat and water. Given their functional importance, maxilloturbinate size and structure are expected to vary predictably among species adapted to different environments. Here the first quantitative analysis is provided of maxilloturbinate structure based on high‐resolution computed tomography (CT) scans of the skulls of eight canid and seven felid species. The key parameters examined were the density of the maxilloturbinate bones within the nasal chamber and how that density varied along the air pathway. In both canids and felids, total maxilloturbinate chamber volume and bone volume increased with body size, with canids having c. 1.5–2.0 times the volume of maxilloturbinate than felids of similar size. In all species, the volume of the maxilloturbinates varies from rostral to caudal, with the peak volu...

The shape of the cranium varies widely among members of the order Carnivora, but the factors that drive the evolution of differences in shape remain unclear. Selection for increased bite force, bite speed or skull strength may all affect cranial morphology. We investigated the relationship between cranial form and function in the trophically diverse dog family, Canidae, using linear morphometrics and finite element (FE) analyses that simulated the internal and external forces that act on the skull during the act of prey capture and killing. In contrast to previous FE‐based studies, we compared models using a newly developed method that removes the effects of size and highlights the relationship between shape and performance. Cranial shape varies among canids based on diet, and different selective forces presumably drove evolution of these phenotypes. The long, narrow jaws of small prey specialists appear to reflect selection for fast jaw closure at the expense of bite force. General...

Synopsis The fossil record of the order Carnivora extends back at least 60 million years and documents a remarkable history of adaptive radiation characterized by the repeated, independent evolution of similar feeding morphologies in distinct clades. Within the order, convergence is apparent in the iterative appearance of a variety of ecomorphs, including cat-like, hyena-like, and wolf-like hypercarnivores, as well as a variety of less carnivorous forms, such as foxes, raccoons, and ursids. The iteration of similar forms has multiple causes. First, there are a limited number of ways to ecologically partition the carnivore niche, and second, the material properties of animal tissues (muscle, skin, bone) have not changed over the Cenozoic. Consequently, similar craniodental adaptations for feeding on different proportions of animal versus plant tissues evolve repeatedly. The extent of convergence in craniodental form can be striking, affecting skull proportions and overall shape, as well as dental morphology. The tendency to evolve highly convergent ecomorphs is most apparent among feeding extremes, such as sabertooths and bone-crackers where performance requirements tend to be more acute. A survey of the fossil record indicates that large hypercarnivores evolve frequently, often in response to ecological opportunity afforded by the decline or extinction of previously dominant hypercarnivorous taxa. While the evolution of large size and carnivory may be favored at the individual level, it can lead to a macroevolutionary ratchet, wherein dietary specialization and reduced population densities result in a greater vulnerability to extinction. As a result of these opposing forces, the fossil record of Carnivora is dominated by successive clades of hypercarnivores that diversify and decline, only to be replaced by new hypercarnivorous clades. This has produced a marvelous set of natural experiments in the evolution of similar ecomorphs, each of which start from phylogenetically and morphologically unique positions. From the symposium ''The Evolution of Feeding Mechanisms in Vertebrates'' presented at the annual meeting of the Society for Integrative and Comparative Biology,

SynopsisTyrannosaurid dinosaurs had large preserved leg muscle attachments and low rotational inertia relative to their body mass, indicating that they could turn more quickly than other large theropods.MethodsTo compare turning capability in theropods, we regressed agility estimates against body mass, incorporating superellipse-based modeled mass, centers of mass, and rotational inertia (mass moment of inertia). Muscle force relative to body mass is a direct correlate of agility in humans, and torque gives potential angular acceleration. Agility scores therefore include rotational inertia values divided by proxies for (1) muscle force (ilium area and estimates of m. caudofemoralis longus cross-section), and (2) musculoskeletal torque. Phylogenetic ANCOVA (phylANCOVA) allow assessment of differences in agility between tyrannosaurids and non-tyrannosaurid theropods (accounting for both ontogeny and phylogeny). We applied conditional error probabilitiesa(p) to stringently test the nul...

Modern birds are derived from a group of carnivorous bipedal dinosaurs known as theropods, with which they share many morphological characteristics [1-7]. For this reason cursorial birds have been widely used as models for understanding the locomotion of their non-avian ancestors (non avian theropods) [8-11]. In our research we have demonstrated that chickens grown with artificial tails exhibit a kinematic locomotive response in their limbs similar to what we would have seen in their extinct ancestors [11]. Our results support the hypothesis that gradual changes in the location of the center of mass resulted in more crouched hind-limb postures, and a shift from hip-driven to knee-driven limb movements through theropod evolution. This suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can potentially be used to gain important insights into previously unexplored aspects of bipedal non-avian theropod locomotion. The wide variabil...

In the dinosaurs, the lateral condyle of the femur is subdivided into two parts, here termed semicondyles: cranial semicondyle which articulates primarily with the fibula, and caudal semicondyle which is known in the theropods as the ectocondylar tuber and articulates with the tibia. Modern birds also have two semicondyles, fibular and tibiofibular ("tibiofibular crest"), which roughly correspond in position to the non-avian theropod semicondyles. However, the basal birds have a single rounded lateral condyle which must have undergone differentiation into two modern avian semicondyles independently of those in the non-avian theropods. Since extrapolating anatomical terms for details of the femoral lateral condyle between modern birds and theropods seems unwarranted, I propose to use two separate, consistent sets of terms, both based on the subdivision of the lateral condyle into two semicondyles, as implemented for modern birds in Table 1.

In order to assess joint loads and to estimate joint reaction forces and net joint torques in human motion analysis, inverse dynamic approaches are commonly applied. These approaches rely on an accurate estimation of human body segment parameter values. The paper gives an overview of contemporary methods with a specific focus on approaches based on geometrical models, where image based or photogrammetric techniques are applied for estimating the parameter values fast and accurately.

Natural history museum collections hold extremely rare, extinct species often described from a single known specimen. On occasions, rediscoveries open new opportunities to understand selective forces acting on phenotypic traits. Recent rediscovery of few individuals of Bocourt´s Terrific Skink Phoboscincus bocourti, from a small and remote islet in New Caledonia allowed to genetically identify a species of land crab in its diet. To explore this further, we CT- and MRI-scanned the head of the holotype, the only preserved specimen dated to about 1870, segmented the adductor muscles of the jaw and bones, and estimated bite force through biomechanical models. These data were compared with those gathered for 332 specimens belonging to 44 other skink species. Thereafter we recorded the maximum force needed to generate mechanical failure of the exoskeleton of a crab specimen. The bite force is greater than the prey hardness, suggesting that predation on hard-shelled crabs may be an importa...

Genetic data of red junglefowl from southern Sumatra is valuable for conservation, unfortunately the data is not yet available. The purpose of this study was to elucidate genetic character, single nucleotide polymorphism, genetic distance, and phylogeny of red junglefowl based on mtDNA COI gene. Blood samples (20 individuals) of red junglefowl were taken from Bengkulu Province and South Sumatra Province from May to November 2021. Total DNA isolation followed the procedure of the Spin-Column Protocol Kit, Qiagen. DNA replication using the Polymerase Chain Reaction technique with specific primers. The results revealed 716 conserved, 16 variable, 9 parsimony, and 6 singleton sites from the 732 bp nucleotide sequence. Six specific sites (SNPs) as barcodes for Sumatran Junglefowl were found at sequences 51, 273, 327, 721, 729, and 732. The mean genetic distance between species was 7.4%. The red junglefowl of South Sumatra Province and Bengkulu Province are closely related with 98% bootstrapping and separated from another Gallus in the same group (ingroup) with 100% bootstrap. Red junglefowl from southern Sumatra has genetic differences from other chickens in the world and these differences can be used as a species barcode and as origin identification the widely traded red junglefowl.

The form and function of the sacrum are of great relevance to understand the evolution of locomotion in tetrapods because it is a key piece of the vertebrate skeleton. The sacrum connects the caudal and presacral regions of the vertebral column and the hindlimbs through the pelvis. Here, we investigate sacrum shape evolution in pinnipeds (Carnivora: Pinnipedia) in relation to terrestrial mammalian carnivorans (fissipeds), and we include crown and stem taxa to quantify the morphological changes they experience in relation to the aquatic environment they inhabit. We use 3D geometric morphometric methods to explore the morphological variability and disparity of the sacrum in a set of terrestrial and aquatic carnivoran species. Our results show that the morphology of the sacrum of each pinniped family is remarkably different and that these differences may be related to the aquatic mode of locomotion (pectoral or pelvic oscillation), the use of hindlimbs to support body weight on land (otariids in contrast with phocids), and the presence or absence of a functional tail. In addition, disparity-through-time analyses indicate that the sacrum of pinnipeds is less constrained than that of fissipeds, which suggests a gravitational origin of such constraints in fissipeds. In conclusion, our results give further support to the important role played by this skeletal structure in the locomotory adaptations of mammals.

SynopsisTyrannosaurid dinosaurs had large preserved leg muscle attachments and low rotational inertia relative to their body mass, indicating that they could turn more quickly than other large theropods.MethodsTo compare turning capability in theropods, we regressed agility estimates against body mass, incorporating superellipse-based modeled mass, centers of mass, and rotational inertia (mass moment of inertia). Muscle force relative to body mass is a direct correlate of agility in humans, and torque gives potential angular acceleration. Agility scores therefore include rotational inertia values divided by proxies for (1) muscle force (ilium area and estimates of m. caudofemoralis longus cross-section), and (2) musculoskeletal torque. Phylogenetic ANCOVA (phylANCOVA) allow assessment of differences in agility between tyrannosaurids and non-tyrannosaurid theropods (accounting for both ontogeny and phylogeny). We applied conditional error probabilitiesa(p) to stringently test the nul...

Determining kinematics of hindlimbs of theropod dinosaurs has been a challenge. Since cursorial birds are phylogenetically closest to theropod dinosaurs they are commonly used as a kinematic model of theropod dinosaur locomotion. Using a comparative biomechanical approach, we found that cursorial birds have a different morphology of legs than non avian theropodos and that appears to be that felines and ungulates share more morphological properties in the hindlimbs with theropod dinosaurs than cursorial birds. We calculated the ratio between the lower leg and the femur, and the relative length of the tibia and the metatarsus with respect to the length of the femur in cursorial birds, as well as felines, ungulates and non-avian theropods. We found that as the length of the femur increases, the length of the lower leg increases similarly in felines, ungulates and non-avian theropods. On the other hand, existing and extinct cursorial birds did not follow this pattern. This observation suggests that the hindlimb of cursorial birds are not well suited to serve as kinematic models for hindlimb of extinct theropod dinosaur locomotion.

We report the first complete sclerotic ring of the Triassic dinosaur Coelophysis bauri from the New Mexico Museum of Natural History's Whitaker Quarry block, C-8-82. The block is from the Apachean Rock Point Formation of the Chinle Group in north-central New Mexico. Specimen P-42200 is a gracile morph of Coelophysis with a skull length of 123 mm, which places it in the large juvenile or small gracile adult range. The anterior orbit and sclerotic ring show no deformation, but the posterior portions show slight elongation in the caudal direction. The orbit has a mean diameter of 31 mm and contains ~20 articulated ossicles preserved in a ring measuring ~21 mm outside diameter, and ~12 mm inside diameter. As preserved, the ring occludes 63% of the orbit. Individual ossicles are sub-trapezoidal to subtriangular, except for the nasal and temporal ossicles, which are more elongate oval in shape. The ossicles show a sigmoid radial cross section. The ossicles typically measure ~7 mm wide (circumferentially) and ~5 mm high (radially), with the wider bases of the elements bounding the corneal aperture. The elongate nasal and temporal ossicles arẽ 10 to 12 mm long and ~5 mm high.

Emus (Dromaius novaehollandiae) are exclusively terrestrial, bipedal and cursorial ratites with some similar biomechanical characteristics to humans. Their growth rates are impressive, as their body mass increases eighty-fold from hatching to adulthood whilst maintaining the same mode of locomotion throughout life. These ontogenetic characteristics stimulate biomechanical questions about the strategies that allow emus to cope with their rapid growth and locomotion, which can be partly addressed via scaling (allometric) analysis of morphology. In this study we have collected pelvic limb anatomical data (muscle architecture, tendon length, tendon mass and bone lengths) and calculated muscle physiological cross sectional area (PCSA) and average tendon cross sectional area from emus across three ontogenetic stages (n = 17, body masses from 3.6 to 42 kg). The data were analysed by reduced major axis regression to determine how these biomechanically relevant aspects of morphology scaled with body mass. Muscle mass and PCSA showed a marked trend towards positive allometry (26 and 27 out of 34 muscles respectively) and fascicle length showed a more mixed scaling pattern. The long tendons of the main digital flexors scaled with positive allometry for all characteristics whilst other tendons demonstrated a less clear scaling pattern. Finally, the two longer bones of the limb (tibiotarsus and tarsometatarsus) also exhibited positive allometry for length, and two others (femur and first phalanx of digit III) had trends towards isometry. These results indicate that emus experience a relative increase in their muscle forcegenerating capacities, as well as potentially increasing the force-sustaining capacities of their tendons, as they grow. Furthermore, we have clarified anatomical descriptions and provided illustrations of the pelvic limb muscle-tendon units in emus.

extant crocodylia are exceptional because they employ almost the full range of quadrupedal footfall patterns ("gaits") used by mammals; including asymmetrical gaits such as galloping and bounding. perhaps this capacity evolved in stem crocodylomorpha, during the triassic when taxa were smaller, terrestrial, and long-legged. However, confusion about which crocodylia use asymmetrical gaits and why persists, impeding reconstructions of locomotor evolution. our experimental gait analysis of locomotor kinematics across 42 individuals from 15 species of Crocodylia obtained 184 data points for a wide velocity range (0.15-4.35 ms −1). our results suggest either that asymmetrical gaits are ancestral for crocodylia and lost in the alligator lineage, or that asymmetrical gaits evolved within crocodylia at the base of the crocodile line. Regardless, we recorded usage of asymmetrical gaits in 7 species of Crocodyloidea (crocodiles); including novel documentation of these behaviours in 5 species (3 critically endangered). Larger crocodylia use relatively less extreme gait kinematics consistent with steeply decreasing athletic ability with size. We found differences between asymmetrical and symmetrical gaits in crocodylia: asymmetrical gaits involved greater size-normalized stride frequencies and smaller duty factors (relative ground contact times), consistent with increased mechanical demands. Remarkably, these gaits did not differ in maximal velocities obtained: whether in Alligatoroidea or Crocodyloidea, trotting or bounding achieved similar velocities, revealing that the alligator lineage is capable of hitherto unappreciated extreme locomotor performance despite a lack of asymmetrical gait usage. Hence asymmetrical gaits have benefits other than velocity capacity that explain their prevalence in crocodyloidea and absence in Alligatoroidea-and their broader evolution. Extant Crocodylia have long been known to use almost all forms of walking and running locomotor modes (e.g., footfall patterns) present in quadrupedal mammals. These gaits include symmetrical (e.g., lateral/diagonal sequence walks; walking and running trots vide 1,2) and asymmetrical (e.g., galloping, bounds and half-bounds) footfall patterns. Nevertheless, the diversity, scaling (body size correlations), and underlying mechanisms of this impressive locomotor repertoire are based only on a few studies of select species from the >23 extant members of Crocodylia. Symmetrical walking gaits have been fairly well studied for Crocodylia, mainly in alligatoroids such as Alligator mississippiensis (also Caiman crocodilus) [ 3-20 and see below]. There have been speculations or anatomical hints of divergent abilities in the "alligator lineage" (Alligatoroidea) vs. "crocodile lineage" (Crocodyloidea) 21-24 , but empirical evidence of any differences in locomotor abilities remains absent. Charig's 25 anecdote of sustained bipedal running in a crocodile (repeated in more recent studies; e.g. 26) is highly specious, never having been reliably documented in that or any subsequent studies. Bounding (synchronized left-right forelimb and hindlimb motions separated by an aerial phase) and galloping (slightly asynchronous left-right motions; essentially a slower version of bounding) gaits have been described for some Crocodylus species, especially C. johnstoni 27,28 , C. porosus 29 and C. niloticus 30,31. It is often misquoted in general media or natural history accounts that C. johnstoni is the only crocodylian known to gallop or bound; some 27 wondered if its bounding ability was "unique" but it is clear that this capacity is more broadly distributed

We review the literature on the geographic and taxonomic diversity of species of lizards and scorpions that are involved in predatoreprey interactions. Somewhat surprisingly, lizards are often the predators in these interactions. Consequently, our goals were to evaluate whether lizard predators had evolved morphological or physiological resistance to scorpion venom or whether the rely on behavioral evasions, and also to document co-evolutionary patterns. Diverse lizards prey on scorpions, but most studies are surprisingly anecdotal. Whether lizard predators tolerate scorpion venom is largely unexplored. Our review highlights opportunities for studies of the evolution of tolerance to scorpion venom by lizards and of the ecology and evolution of lizardescorpion interactions in arid zones. Progress will be facilitated by collaborations between experts in ecology and toxicology, and by incorporating molecular approaches such as proteomics and transcriptomics. Much is to be learned about scorpion venoms and their effects on predators, with potential benefits to humans.

We describe a new specimen attributed toMacranhinga ranzii, a taxon whose holotype is a left femur, being collected from rocks in the Solimões formation, Southwestern Amazon. The new material is an almost complete pelvic girdle and synsacrum (UFAC 6471), collected in a new fossiliferous locality named Cajueiro. The compatibility between the diameter of foramen acetabuli of UFAC 6471 with the caput femoris of the holotype and the synapomorphies present in the specimen allowed us to attribute it to M. ranzii and emend the diagnosis for this species. Based on three linear measurements of the pelvic girdle and the medium weight of extant Anhinga, we estimate the adult animal's body mass at 8.6 kg. The phylogenetic inference resulted in two equally probable evolutionary hypotheses: one of them with a monophyletic Macranhinga and in the other Meganhinga chilensis as the sister clade of a Macranhinga (in part) plus Anhinga clade. In both scenarios, Macranhinga ranzii is closely related to G. kiyuensis. The morphological and myological data gained in this study enabled us to recognise Macranhinga ranzii as a proficient swimmer and diver, and consequentially a skilled fish hunter in deep waters.

Variations in craniodental morphology have been correlated to feeding adaptations in living organisms and used as proxies for paleodiet reconstruction. Within the mammalian order Carnivora, the Miocene fossil musteloid Leptarctus has been variably interpreted as a carnivore, frugivore, herbivore, omnivore, or insectivore based on morphological comparisons with extant species. Here, we perform the first simulation of cranial biomechanics in Leptarctus primus, aiming to identify a living analogue using biomechanical capability rather than qualitative morphology. Finite element models (FEMs) of 18 extant carnivorans and two extinct outgroup taxa were used to compare known dietbiomechanics relationships with the biomechanical properties of L. primus FEMs within a phylogenetic context. Multivariate analyses of simulated bite efficiency and skull stiffness values indicate that L. primus is most similar overall to Taxidea taxus (American badger) in unilateral bite simulations. Based on biomechanical predictions, we postulate that L. primus resembled the American badger in its feeding ecology more closely than any other taxon tested and thus conclude that L. primus was dominantly a carnivore with an auxiliary feeding capability of omnivory. We also compared the L. primus FEMs with the potentially synonymous Hypsoparia bozemanensis to determine a possible range of feeding capabilities. We observed an increase in mechanical efficiency with a deepening of the zygomae of H. bozemanensis, a trait previously used to differentiate it from L. primus. Ongoing work to expand the database of cranial biomechanical simulation data across Carnivoramorpha should help to further clarify evolutionary patterns of skull biomechanical specializations in musteloids and other carnivorans.

Natural history museum collections hold extremely rare, extinct species often described from a single known specimen. On occasions, rediscoveries open new opportunities to understand selective forces acting on phenotypic traits. Recent rediscovery of few individuals of Bocourt´s Terrific Skink Phoboscincus bocourti, from a small and remote islet in New Caledonia allowed to genetically identify a species of land crab in its diet. To explore this further, we CT- and MRI-scanned the head of the holotype, the only preserved specimen dated to about 1870, segmented the adductor muscles of the jaw and bones, and estimated bite force through biomechanical models. These data were compared with those gathered for 332 specimens belonging to 44 other skink species. Thereafter we recorded the maximum force needed to generate mechanical failure of the exoskeleton of a crab specimen. The bite force is greater than the prey hardness, suggesting that predation on hard-shelled crabs may be an importa...

SynopsisTyrannosaurid dinosaurs had large preserved leg muscle attachments and low rotational inertia relative to their body mass, indicating that they could turn more quickly than other large theropods.MethodsTo compare turning capability in theropods, we regressed agility estimates against body mass, incorporating superellipse-based modeled mass, centers of mass, and rotational inertia (mass moment of inertia). Muscle force relative to body mass is a direct correlate of agility in humans, and torque gives potential angular acceleration. Agility scores therefore include rotational inertia values divided by proxies for (1) muscle force (ilium area and estimates of m. caudofemoralis longus cross-section), and (2) musculoskeletal torque. Phylogenetic ANCOVA (phylANCOVA) allow assessment of differences in agility between tyrannosaurids and non-tyrannosaurid theropods (accounting for both ontogeny and phylogeny). We applied conditional error probabilitiesa(p) to stringently test the nul...

Avian origins revisited The recent discovery of the fossil dinosaur Microraptor, in which all four limbs are endowed with feathers that are shaped like flight-feathers with asymmetrical vanes (Xu et al 2003), and the analysis, a week earlier, of "wing-assisted incline running" by galliform birds (Dial 2003) are exciting contributions towards a more complete understanding of present and past organismal biodiversity. But this was not the reason why both articles received more than their share of media attention. Both articles asserted, as had many before, that they were providing evidence that would help solve a central part of the current controversy surrounding the evolutionary origin of birds. Xu et al (2003) interpreted the bird-sized, 77 cm long Microraptor gui as a dinosaur with flight feathers along the forelimbs, hindlimbs, and tail that formed airfoils enabling Microraptor to glide from tree to tree. Based on these morphological data and functional inferences, Xu et al (2003) see Microraptor as representing an intermediate stage between a flightless, bipedal non-avian theropod dinosaur and an arboreal volant bird capable of flapping flight. Dial (2003), in contrast, observed living chukar partridges assisting their bipedal walk on inclined surfaces by flapping their wings. From these observations, he conjectured that flying birds might have evolved from a bipedal, cursorial dinosaur ancestor by passing through an intermediate organism that used wing-flapping to climb into trees. Xu et al (2003) and Dial (2003) both accept that dinosaurs are the ancestors of modern birds, but otherwise stand on opposite sides of the current controversy concerning the evolution of feathers, avian flight, and birds. Xu et al (2003) assume that birds and avian flight evolved from an arboreal ancestor that was able to glide; they support the "trees-down" version of avian evolution. Dial (2003), in contrast, assumes that birds and avian flight evolved from a cursorial ancestor that was able to lift off the ground by flapping its forelimbs; he supports the "ground-up" version of avian evolution. At first view, the controversy concerning the origin and evolution of feathers, avian flight, and birds may be seen as a model for how science works: Competition between proponents of opposing hypotheses leads to a winning theory by majority vote of the scientific community. This image seems to be so compelling that news media started to cover the evolving scientific drama about a decade ago (for some recent examples, see Gorman 2003; Meek 2003; Wilford 2003). But is this image a realistic representation of how macroevolutionary questions are, or should, be addressed and solved? And why was the study by Tobalske et al (2003) not also highlighted by the media, even though it was published in the same issue of the journal Nature as the article by Xu et al (2003), and even though it analysed the relationships between a bird's morphology, flight style, wing beat frequency, power output, and flight velocity? Could the reason be that the paper by Tobalske et al (2003) did not mention explicitly its relevance, ultimately, for a better understanding of the evolutionary origin of avian flight? In the last 150 years, our understanding of the evolutionary history of birds has made enormous strides. When Darwin published his theory in1859, birds were viewed as a clearly delimited vertebrate class that was as different from the other tetrapod classes as those are from fish-like vertebrates. Feathers and wing-like forelimbs set birds apart from all vertebrates to such a degree that it was farfetched to conceive a reptilian ancestry for birds. Then, in 1861, the first fossil feather and, shortly thereafter, a fossil bird, Archaeopteryx, with feathers preserved in situ, were discovered from Jurassic deposits (e.g. Bühler and Bock 2002). This fossil was hailed as a "missing link" that had been predicted by Darwin's theory, as it clearly comprised avian as well as reptilian characteristics. And almost immediately, two opposing theories emerged concerning the evolutionary origin of birds, namely an origin either from a cursorial dinosaurian ancestor or from a gliding arboreal reptilian ancestor (Bowler 1996). Subsequent discoveries of dinosaurian and reptilian fossils, as well as an expansion of studies of avian anatomy and biology, led to a first coherent evolutionary scenario (Heilmann 1927

The aim of this study was to compare the arterial vascularization of the pelvic limb between southern caracara (Caracara plancus) and great egret (Ardea alba) by dissection and radiographic examinations. Five specimens of caracaras (three males and two females), and seven great egrets (five males and two females) were used. Barium sulphate and latex suspension were injected into the left ventricle of the birds. The radiographs were taken with the pelvic limbs in the ventrodorsal, dorsoplantar, mediolateral and lateromedial recumbency. Thereafter, the material was fixed in a 10% solution of formaldehyde and dissected. The pelvic limb received its arterial supply from two main vessels, the ischiatic and external iliac arteries. The ischiatic artery presented to be the principal artery of pelvic limb in the caracara and great egret. Several branches arised from the ischiatic and external iliac arteries were described. No gender differences were observed in both species. The caracara an...

Machimosaurus was a large-bodied durophagous/chelonivorous genus of teleosaurid crocodylomorph that lived in shallow marine and brackish ecosystems during the Late Jurassic. Among teleosaurids, Machimosaurus and its sister taxon 'Steneosaurus' obtusidens are characterized by having foreshortened rostra, proportionally enlarged supratemporal fenestrae and blunt teeth with numerous apicobasal ridges and a shorter anastomosed ridged pattern in the apical region. A recent study on 'S.' obtusidens dentition found both true denticles and false serrations (enamel ridges which contact the carinae). Here, we comprehensively describe and figure the dentition of Machimosaurus, and find that Machimosaurus buffetauti and Machimosaurus hugii have four types of serration or serrationlike structures, including both denticles and false denticles on the carinae. The denticles are irregularly shaped and are not always discrete units, whereas the false denticles caused by the interaction between the superficial enamel ridges and the carinae are restricted to the apical region. Peculiarly, the most 'denticlelike' structures are discrete, bulbous units on the apicobasal and apical anastomosed ridges of M. hugii. These 'pseudodenticles' have never, to our knowledge, previously been reported among crocodylomorphs, and their precise function is unclear.

The Infectious Diseases Data Observatory (IDDO, https://www.iddo.org) has launched a clinical data platform for the collation, curation, standardisation and reuse of individual participant data (IPD) on treatments for two of the most globally important neglected tropical diseases (NTDs), schistosomiasis (SCH) and soiltransmitted helminthiases (STHs). This initiative aims to harness the power of data-sharing by facilitating collaborative joint analyses of pooled datasets to generate robust evidence on the efficacy and safety of anthelminthic treatment regimens. A crucial component of this endeavour has been the development of a Research Agenda to

Therian mammals are known to move their forelimbs in a parasagittal plane, retracting the mobilised scapula during stance phase. Non-cursorial therian mammals often abduct the elbow out of the shoulder-hip parasagittal plane. This is especially prominent in Tamandua (Xenarthra), which suggests they employ aspects of sprawling (e.g. lizard-like) locomotion. Here, we tested whether tamanduas use sprawling forelimb kinematics, i.e. a largely immobile scapula with pronounced lateral spine bending and long-axis rotation of the humerus. We analysed high-speed videos and used X-ray motion analysis of tamanduas walking and balancing on branches of varying inclinations and provide a quantitative characterization of gaits and forelimb kinematics. Tamanduas displayed lateral sequence/lateral couplets on flat ground and horizontal branches, but increased diagonality on steeper inclines and declines, resulting in lateral sequence/diagonal couplets gaits. This result provides further evidence for high diagonality in arboreal species, probably maximising stability in arboreal environments. Further, the results reveal a mosaic of sprawling and parasagittal kinematic characteristics. The abducted elbow results from a constantly internally rotated scapula about its long axis and a retracted humerus. Scapula retraction contributes considerably to stride length. However, lateral rotation in the pectoral region of the spine (range: 21 deg) is higher than reported for other therian mammals. Instead, it is similar to that of skinks and alligators, indicating an aspect generally associated with sprawling locomotion is characteristic for forelimb kinematics of tamanduas. Our study contributes to a growing body of evidence of highly variable noncursorial therian mammal locomotor kinematics.

Human patellae (kneecaps) are thought to act as gears, altering the mechanical advantage of knee extensor muscles during running. Similar sesamoids have evolved in the knee extensor tendon independently in birds, but it is unknown if these also affect the mechanical advantage of knee extensors. Here, we examine the mechanics of the patellofemoral joint in the helmeted guineafowl Numida meleagris using a method based on muscle and tendon moment arms taken about the patella&#39;s rotation centre around the distal femur. Moment arms were estimated from a computer model representing hindlimb anatomy, using hip, knee and patellar kinematics acquired via marker‐based biplanar fluoroscopy from a subject running at 1.6 ms−1 on a treadmill. Our results support the inference that the patella of Numida does alter knee extensor leverage during running, but with a mechanical advantage generally greater than that seen in humans, implying relatively greater extension force but relatively lesser ex...