United Kingdom physiotherapists injection therapy practice for musculoskeletal complaints: A cross-sectional survey.

BACKGROUND: Physiotherapists in the United Kingdom (UK), who have received additional training can adopt injection therapy for the treatment of musculoskeletal (MSK) disorders. OBJECTIVES: The objective of this practice survey was to explore (i) the frequency of use of injection therapy by UK physiotherapists for MSK disorders; and (ii) the clinical reasoning for selection of injectate, dose and pre/post injection practice. DESIGN: Cross-sectional online survey. METHODS: The online survey was disseminated via social media and professional networks over a 3-month period. Responses to closed multiple choice survey questions were analysed with descriptive data, with reporting of confidence intervals at 95%. Open questions were analysed using content analysis. RESULTS: The survey received 320 responses. The majority (86.6%, n = 277) used landmark guided approaches. The highest frequency of injections administered were for trigger digits, sub acromial pain and the knee joint. Corticosteroid drugs were widely used (99.7%, n = 319, CI 95% 98 to 100) with Triamcinolone (Kenalog) being the most frequently utilised for both joints (58.8%, n = 160, 53 to 65) and soft tissues (46.3%, n = 126, 40 to 52). Drug choice was largely based on availability in clinic (47.1%, n = 128, 41 to 53). Drug doses for common injection sites varied among the respondents with variation also evident in pre and post-injection practice. CONCLUSION: Marked variation across some elements of injection therapy practice was evident. Notable differences in corticosteroid preparation used, the doses of drug injected, and the use of local anaesthetic were reported by respondents. Injecting physiotherapists should endeavour to ensure practice is aligned to best available evidence.

Anatomically grounded estimation of hindlimb muscle sizes in Archosauria.

In vertebrates, active movement is driven by muscle forces acting on bones, either directly or through tendinous insertions. There has been much debate over how muscle size and force are reflected by the muscular attachment areas (AAs). Here we investigate the relationship between the physiological cross-sectional area (PCSA), a proxy for the force production of the muscle, and the AA of hindlimb muscles in Nile crocodiles and five bird species. The limbs were held in a fixed position whilst blunt dissection was carried out to isolate the individual muscles. AAs were digitised using a point digitiser, before the muscle was removed from the bone. Muscles were then further dissected and fibre architecture was measured, and PCSA calculated. The raw measures, as well as the ratio of PCSA to AA, were studied and compared for intra-observer error as well as intra- and interspecies differences. We found large variations in the ratio between AAs and PCSA both within and across species, but muscle fascicle lengths are conserved within individual species, whether this was Nile crocodiles or tinamou. Whilst a discriminant analysis was able to separate crocodylian and avian muscle data, the ratios for AA to cross-sectional area for all species and most muscles can be represented by a single equation. The remaining muscles have specific equations to represent their scaling, but equations often have a relatively high success at predicting the ratio of muscle AA to PCSA. We then digitised the muscle AAs of Coelophysis bauri, a dinosaur, to estimate the PCSAs and therefore maximal isometric muscle forces. The results are somewhat consistent with other methods for estimating force production, and suggest that, at least for some archosaurian muscles, that it is possible to use muscle AA to estimate muscle sizes. This method is complementary to other methods such as digital volumetric modelling.

A proposed standard for quantifying 3-D hindlimb joint poses in living and extinct archosaurs.

The last common ancestor of birds and crocodylians plus all of its descendants (clade Archosauria) dominated terrestrial Mesozoic ecosystems, giving rise to disparate body plans, sizes, and modes of locomotion. As in the fields of vertebrate morphology and paleontology more generally, studies of archosaur skeletal structure have come to depend on tools for acquiring, measuring, and exploring three-dimensional (3-D) digital models. Such models, in turn, form the basis for many analyses of musculoskeletal function. A set of shared conventions for describing 3-D pose (joint or limb configuration) and 3-D kinematics (change in pose through time) is essential for fostering comparison of posture/movement among such varied species, as well as for maximizing communication among scientists. Following researchers in human biomechanics, we propose a standard methodological approach for measuring the relative position and orientation of the major segments of the archosaur pelvis and hindlimb in 3-D. We describe the construction of anatomical and joint coordinate systems using the extant guineafowl and alligator as examples. Our new standards are then applied to three extinct taxa sampled from the wider range of morphological, postural, and kinematic variation that has arisen across >250 million years of archosaur evolution. These proposed conventions, and the founding principles upon which they are based, can also serve as starting points for measuring poses between elements within a hindlimb segment, for establishing coordinate systems in the forelimb and axial skeleton, or for applying our archosaurian system more broadly to different vertebrate clades.

Cranial functional morphology of the pseudosuchian Effigia and implications for its ecological role in the Triassic.

Pseudosuchians, archosaurian reptiles more closely related to crocodylians than to birds, exhibited high morphological diversity during the Triassic with numerous examples of morphological convergence described between Triassic pseudosuchians and post-Triassic dinosaurs. One example is the shuvosaurid Effigia okeeffeae which exhibits an "ostrich-like" bauplan comprising a gracile skeleton with edentulous jaws and large orbits, similar to ornithomimid dinosaurs and extant palaeognaths. This bauplan is regarded as an adaptation for herbivory, but this hypothesis assumes morphological convergence confers functional convergence, and has received little explicit testing. Here, we restore the skull morphology of Effigia, perform myological reconstructions, and apply finite element analysis to quantitatively investigate skull function. We also perform finite element analysis on the crania of the ornithomimid dinosaur Ornithomimus edmontonicus, the extant palaeognath Struthio camelus and the extant pseudosuchian Alligator mississippiensis to assess the degree of functional convergence with a taxon that exhibit "ostrich-like" bauplans and its closest extant relatives. We find that Effigia possesses a mosaic of mechanically strong and weak features, including a weak mandible that likely restricted feeding to the anterior portion of the jaws. We find limited functional convergence with Ornithomimus and Struthio and limited evidence of phylogenetic constraints with extant pseudosuchians. We infer that Effigia was a specialist herbivore that likely fed on softer plant material, a niche unique among the study taxa and potentially among contemporaneous Triassic herbivores. This study increases the known functional diversity of pseudosuchians and highlights that superficial morphological similarity between unrelated taxa does not always imply functional and ecological convergence.

Recommendations on patient-facing websites regarding diagnostic imaging for low back, knee, and shoulder pain: A scoping review.

Objective: To describe and synthesise the content of public-facing websites regarding the use of diagnostic imaging for adults with lower back pain, knee, and shoulder pain. Methods: Scoping review conducted in accordance with PRISMA guidance. A Google search was performed to identify public-facing websites that were either United Kingdom-based, or National Health Service affiliated. The DISCERN tool was used to appraise website quality before information regarding the use of imaging was synthesised using thematic analysis. Results: Eighty-six websites were included, with 48 making reference to the use of imaging. The information within the majority (n = 43) of public-facing websites aligns with best available evidence. Where there is inconsistency, this may be explained by lower website quality. Three themes were apparent regarding the use of imaging - imaging to inform diagnosis and management; imaging in context; patient experience and expectations. Conclusion: The recommendations and rationale for use of imaging contained within public-facing websites does not appear to justify the increase in imaging rates for musculoskeletal pain in the UK. Innovation: Publicly available information following a novel search strategy, is largely aligned with best evidence, further understanding is required to determine reasons for requesting imaging from a patient and clinician perspective.

Base of thumb osteoarthritis in UK interface services-a cohort and survey-based study to assess current practice.

OBJECTIVE: Base of thumb OA (BTOA) is a common age-related disease that has a significant negative impact on quality of life, while little is known about the structure and pathways of interface services. Our aim was to assess disease burden, referral pathways, service structure and management pathways in UK interface services. METHODS: A structured questionnaire was carried out with a participating clinician at each centre to detail the local guidelines and management of BTOA. Five patients referred with BTOA were prospectively identified in each of 32 UK interface centres. RESULTS: Most centres (72%) had a local guideline and a standardized treatment regime consisting of education (100%), joint protection (100%), range of motion exercises (84%), strengthening exercises (88%), splintage (100%) and use of assistive devices (78%). No centre routinely offered a steroid injection at the first appointment and no centre had a specific threshold for offering an injection. Injection delivery was variable. Most patients had not been referred previously (82%). Most patients used analgesia (72%), but a minority of patients had been treated with a splint (46%), therapy (43%) and steroid injection (27%) prior to their latest attendance. CONCLUSION: Most BTOA patients newly referred to interface services have been treated with analgesics and have not received comprehensive multimodal intervention. The management of BTOA at interface services is standardized in terms of education, splintage and therapy. However, there is a lack of standardization in terms of both the threshold for, timing of and mode of delivery of injection therapy.

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.

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.

Musculoskeletal modelling of the Nile crocodile (Crocodylus niloticus) hindlimb: Effects of limb posture on leverage during terrestrial locomotion.

We developed a three-dimensional, computational biomechanical model of a juvenile Nile crocodile (Crocodylus niloticus) pelvis and hindlimb, composed of 47 pelvic limb muscles, to investigate muscle function. We tested whether crocodiles, which are known to use a variety of limb postures during movement, use limb orientations (joint angles) that optimise the moment arms (leverages) or moment-generating capacities of their muscles during different limb postures ranging from a high walk to a sprawling motion. We also describe the three-dimensional (3D) kinematics of the crocodylian hindlimb during terrestrial locomotion across an instrumented walkway and a treadmill captured via X-ray Reconstruction of Moving Morphology (biplanar fluoroscopy; 'XROMM'). We reconstructed the 3D positions and orientations of each of the hindlimb bones and used dissection data for muscle lines of action to reconstruct a focal, subject-specific 3D musculoskeletal model. Motion data for different styles of walking (a high, crouched, bended and two types of sprawling motion) were fed into the 3D model to identify whether any joints adopted near-optimal poses for leverage across each of the behaviours. We found that (1) the hip adductors and knee extensors had their largest leverages during sprawling postures and (2) more erect postures typically involved greater peak moment arms about the hip (flexion-extension), knee (flexion) and metatarsophalangeal (flexion) joints. The results did not fully support the hypothesis that optimal poses are present during different locomotory behaviours because the peak capacities were not always reached around mid-stance phase. Furthermore, we obtained few clear trends for isometric moment-generating capacities. Therefore, perhaps peak muscular leverage in Nile crocodiles is instead reached either in early/late stance or possibly during swing phase or other locomotory behaviours that were not studied here, such as non-terrestrial movement. Alternatively, our findings could reflect a trade-off between having to execute different postures, meaning that hindlimb muscle leverage is not optimised for any singular posture or behaviour. Our model, however, provides a comprehensive set of 3D estimates of muscle actions in extant crocodiles which can form a basis for investigating muscle function in extinct archosaurs.

Rapid implementation and improvement of a virtual student placement model in response to the COVID-19 pandemic.

Practice-based learning via clinical placement is a core part of a physiotherapy degree with the Chartered Society of Physiotherapy requiring completion of 1000 placement hours over a preregistration degree programme. In April 2020, as a result of the COVID-19 pandemic and subsequent lockdown Connect Health had to cancel 10 student placements as we transitioned to virtual consultations for all clinics. This cancellation of student placements was replicated across the nation with many Higher Education Institutes reporting a backlog of student placements. Without the requisite placement hours students are unable to progress into the next academic year or are unable to graduate. This then reduces the flow of new-graduate physiotherapists into the workforce at a time when there is a plan to grow the physiotherapy workforce to meet primary care demand. In response to this problem a novel placement model to facilitate virtual student placements ('virtual placements') was developed, tested and then rolled out across Connect Health using the Plan-Do-Study-Act quality improvement methodology. The model combines shadowing a broad range of virtual clinics with delivery of patient-facing online exercise classes via the Facebook Live platform and completion of virtual projects to support knowledge consolidation. This virtual student placement model enabled an increase in student capacity of over 400% compared with 2018-2019 with 182 students starting between May and August 2020. The model runs using widely available technology, requires no additional investment and has enabled these students to continue their studies and progress towards qualifying as physiotherapists.

Musculoskeletal risk stratification tool to inform a discussion about face-to-face assessment during the COVID-19 pandemic.

The COVID-19 pandemic and lockdown caused clinicians in the UK to switch to delivering musculoskeletal care using telephone or video consultations. NHS England (an executive non-departmental public body of the Department of Health and Social Care, England) recommended prioritisation of more urgent conditions, including those people whose condition has deteriorated and those waiting the longest as part of a phased return to pre-COVID-19 service provision. Clinicians will need to assess an individual's risk factors for complications from COVID-19 alongside their clinical priority to inform a shared decision-making discussion about appropriate face-to-face care delivery. This paper outlines a risk stratification tool that informs that discussion and aims to reduce the subjectivity in the risk assessment between clinicians.

Mandibular nerve block in juvenile Nile crocodile: a cadaveric study.

OBJECTIVE: To develop a technique for performing the mandibular nerve block in Nile crocodiles. STUDY DESIGN: Experimental cadaveric study. ANIMALS: A total of 16 juvenile Nile crocodile heads. METHODS: To study the course of the mandibular nerve, one head was dissected. Computed tomography (CT) examination was performed in two heads to identify useful landmarks. Thereafter, a hypodermic needle was inserted through the external mandibular fenestra of 17 hemimandibles (13 heads), and a mixture of methylene blue and iohexol was injected. Injection volumes were 0.5 (n = 7) and 1.0 mL (n = 10) for hemimandibles < 15 and ≥ 15 cm long, respectively. Iohexol spread and nerve staining with methylene blue were assessed with CT and anatomical dissection, respectively. Data were analysed with one-sample t test or Mann-Whitney U test. Significance was set at p < 0.05. RESULTS: Both anatomical dissection and imaging confirmed the external mandibular fenestra as a useful anatomical landmark for needle insertion. The CT images acquired after needle positioning confirmed that its tip was located on the medial bony mandibular surface formed by the fusion of the angular and coronoid bones in 100% cases. In all the hemimandibles, the rostrocaudal spread of contrast was > 23 mm. The length of the stained mandibular nerve in the temporal region and of the stained medial branch of the mandibular nerve, as well as the dorsoventral and mediolateral spread of iohexol, was greater in group 1.0 than in group 0.5 (p < 0.001). The caudal spread of iohexol was greater in group 1.0 than in group 0.5 (p = 0.01). CONCLUSIONS AND CLINICAL RELEVANCE: The technique developed in this study is feasible. Both injection volumes resulted in staining of the mandibular nerve. The spread of contrast in the anatomical region of interest may result in successful sensory block.

Guidelines for the use of diagnostic imaging in musculoskeletal pain conditions affecting the lower back, knee and shoulder: A scoping review.

BACKGROUND: Musculoskeletal (MSK) pain is one of the most common reasons for primary care consultation, particularly pain in the lower back (LBP), knee and shoulder. The use of diagnostic imaging for MSK pain is increasing, but it is unclear whether this increase is justified on the basis of clinical practice guideline (CPG) recommendations. AIM: To identify and map the content of CPGs that informs the use of diagnostic imaging in those with nontraumatic LBP, knee and shoulder pain in primary and intermediate care in the UK. DESIGN AND SETTING: A scoping review of CPGs. METHODS: This scoping review was conducted and is reported in accordance with PRISMA guidance. A broad search strategy included electronic searches of MEDLINE, CINAHL, PsychINFO and SPORTDiscus from 2009 to 17 April 2019. This was conducted alongside a search of guideline repositories and was combined with a snowball search of Google, relevant professional bodies and use of social media. RESULTS: 31 relevant CPGs were included. Routine use of diagnostic imaging for those with nontraumatic LBP, knee or shoulder pain is generally discouraged in primary care or intermediate care. Diagnostic imaging should be reserved for when specific or serious pathology is suspected or where the person is not responding to initial nonsurgical management and the imaging result is expected to change clinical management decisions. CONCLUSION: Diagnostic imaging should not be routinely requested in primary or intermediate care for nontraumatic LBP, knee or shoulder pain. CPGs do not justify the increasing imaging rates in the UK for MSK pain.

Decelerated dinosaur skull evolution with the origin of birds.

The evolutionary radiation of birds has produced incredible morphological variation, including a huge range of skull form and function. Investigating how this variation arose with respect to non-avian dinosaurs is key to understanding how birds achieved their remarkable success after the Cretaceous-Paleogene extinction event. Using a high-dimensional geometric morphometric approach, we quantified the shape of the skull in unprecedented detail across 354 extant and 37 extinct avian and non-avian dinosaurs. Comparative analyses reveal fundamental differences in how skull shape evolved in birds and non-avian dinosaurs. We find that the overall skull shape evolved faster in non-avian dinosaurs than in birds across all regions of the cranium. In birds, the anterior rostrum is the most rapidly evolving skull region, whereas more posterior regions-such as the parietal, squamosal, and quadrate-exhibited high rates in non-avian dinosaurs. These fast-evolving elements in dinosaurs are strongly associated with feeding biomechanics, forming the jaw joint and supporting the jaw adductor muscles. Rapid pulses of skull evolution coincide with changes to food acquisition strategies and diets, as well as the proliferation of bony skull ornaments. In contrast to the appendicular skeleton, which has been shown to evolve more rapidly in birds, avian cranial morphology is characterised by a striking deceleration in morphological evolution relative to non-avian dinosaurs. These results may be due to the reorganisation of skull structure in birds-including loss of a separate postorbital bone in adults and the emergence of new trade-offs with development and neurosensory demands. Taken together, the remarkable cranial shape diversity in birds was not a product of accelerated evolution from their non-avian relatives, despite their frequent portrayal as an icon of adaptive radiations.

Anesthesia and Anesthetic-Related Complications of 8 Elegant-Crested Tinamous (Eudromia elegans) Undergoing Experimental Surgery.

The aim of this study was to describe the anesthetic effects of an injectable anesthetic protocol, based on ketamine, midazolam, and medetomidine, followed by inhalational sevoflurane, in 8 elegant-crested tinamous (Eudromia elegans) undergoing experimental surgery. Initial doses for both injectable agents were tested in 1 bird and then refined with an algorithm based on the effects observed in the pilot procedure. Heart and respiratory rates, as well as nociceptive reflexes, were evaluated before anesthesia (baseline) and intraoperatively, at 10 minute intervals. The time from injection to anesthetic induction and surgical anesthesia, as well as the time from atipamezole injection to recovery, was recorded for each bird. The median doses of medetomidine and ketamine were 0.075 mg/kg and 33 mg/kg, respectively. Anesthetic induction was achieved within 10 (range, 4-45) minutes from intramuscular injection, whereas time to surgical anesthesia was 22 ±16 minutes. The baseline heart rate values were significantly higher than those measured intraoperatively at any time point (P = .001). Intraoperatively, 5 of 8 tinamous (63%) developed cardiac arrhythmias. Other encountered complications were regurgitation in 2 birds (25%), cardiac arrest in 1 bird (13%) soon after injection of the anesthetic agents, and prolonged recovery in another bird (13%), which was euthanized. Necropsy of the 2 fatal outcomes (25%) showed evidence of hepatic lipidosis in both (100%) and intramyocardial fat accumulation in 1 bird (50%). This report highlights the challenges of tinamou anesthesia. Cardiac complications are common in this species, and close monitoring of intraoperative cardiovascular variables is recommended for prompt recognition and treatment.

Examination of the neck when a patient complains of shoulder pain: a global survey of current practice (2019).

BACKGROUND: Shoulder pain is a common musculoskeletal problem. Despite this, much uncertainty still exists regarding diagnosis, prognosis and effectiveness of treatments. One diagnostic challenge is determining the role of the neck when a patient complains of shoulder pain. The aim of this survey was to investigate healthcare professionals' indications for examining the neck in this case and subsequent methods used. METHODS: An online survey was developed and distributed via Twitter and the authors' professional networks. Responses were collected over a 4-week period in 2019. RESULTS: In total, 918 respondents replied; 804 completed the full survey. The majority were physiotherapists. Over 80% would examine the neck of patients presenting with shoulder pain. The most commonly used method was neck active range-of-movement testing (n = 822/95.3%), followed by neurological examination (n = 713/78.1%). Less commonly used tests were neck resistance testing, palpation of the neck and Spurling's test. Fewer numbers (n = 176/22%) resorted to using diagnostic tests such as imaging. CONCLUSIONS: This survey provides some insight as to how healthcare practitioners examine the neck when a patient complains of shoulder pain. Most would examine based on anterolateral shoulder pain, using variable combinations of movement, resistance, neurological and palpation/other testing. A minority would perform diagnostics or imaging. The results of the survey highlight that practice in this area is mixed, which may be due to uncertainty regarding optimal methods. This highlights the need for further work to understand this clinical dilemma better.

Greater trochanteric pain syndrome in the UK National Health Service: A multicentre service evaluation.

PURPOSE: Greater trochanteric pain syndrome (GTPS) is a debilitating condition causing lateral hip pain. A recent randomized controlled trial (LEAP) demonstrated that exercise interventions for GTPS provided superior outcomes, compared with corticosteroid injection and wait-and-see approaches. However, participants were not patients seeking care and therefore may not have represented the typical patient seen within the National Health Service (NHS). The present service evaluation aimed to provide data on the characteristics of patients with GTPS presenting to NHS physiotherapy services, to enable consideration of the applicability of the findings of the LEAP trial to patients seeking care within the NHS. METHODS: Four NHS sites provided anonymized data on patients presenting to their service with a primary complaint of GTPS. RESULTS: The data from 162 patients suggested that the typical patients presenting to the NHS with GTPS are female (73%), overweight (body mass index 28.5) and experiencing a 12-month or longer history of lateral hip pain (56.8%). Patients reported high levels of pain (visual analogue score 6.5), low health-related quality of life (EuroQol five-dimensions - 5-level score 0.6), coexisting medical conditions (79.0%) and high medication use (82.7%). CONCLUSIONS: Patients presenting to the NHS with GTPS appear to have multifactorial issues, with high levels of pain and disability, and are often medicated for multiple coexisting conditions. These characteristics differentiate them from patients recruited to the LEAP trial. Hence, it is unclear whether the findings of the LEAP trial are applicable to patients with GTPS who consult physiotherapy services in the NHS. Further research is warranted to evaluate this.

Ontogenetic changes in the body plan of the sauropodomorph dinosaur Mussaurus patagonicus reveal shifts of locomotor stance during growth.

Ontogenetic information is crucial to understand life histories and represents a true challenge in dinosaurs due to the scarcity of growth series available. Mussaurus patagonicus was a sauropodomorph dinosaur close to the origin of Sauropoda known from hatchling, juvenile and mature specimens, providing a sufficiently complete ontogenetic series to reconstruct general patterns of ontogeny. Here, in order to quantify how body shape and its relationship with locomotor stance (quadruped/biped) changed in ontogeny, hatchling, juvenile (~1 year old) and adult (8+ years old) individuals were studied using digital models. Our results show that Mussaurus rapidly grew from about 60 g at hatching to ~7 kg at one year old, reaching >1000 kg at adulthood. During this time, the body's centre of mass moved from a position in the mid-thorax to a more caudal position nearer to the pelvis. We infer that these changes of body shape and centre of mass reflect a shift from quadrupedalism to bipedalism occurred early in ontogeny in Mussaurus. Our study indicates that relative development of the tail and neck was more influential in determining the locomotor stance in Sauropodomorpha during ontogeny, challenging previous studies, which have emphasized the influence of hindlimb vs. forelimb lengths on sauropodomorph stance.

Evolutionary Integration and Modularity in the Archosaur Cranium.

Complex structures, like the vertebrate skull, are composed of numerous elements or traits that must develop and evolve in a coordinated manner to achieve multiple functions. The strength of association among phenotypic traits (i.e., integration), and their organization into highly-correlated, semi-independent subunits termed modules, is a result of the pleiotropic and genetic correlations that generate traits. As such, patterns of integration and modularity are thought to be key factors constraining or facilitating the evolution of phenotypic disparity by influencing the patterns of variation upon which selection can act. It is often hypothesized that selection can reshape patterns of integration, parceling single structures into multiple modules or merging ancestrally semi-independent traits into a strongly correlated unit. However, evolutionary shifts in patterns of trait integration are seldom assessed in a unified quantitative framework. Here, we quantify patterns of evolutionary integration among regions of the archosaur skull to investigate whether patterns of cranial integration are conserved or variable across this diverse group. Using high-dimensional geometric morphometric data from 3D surface scans and computed tomography scans of modern birds (n = 352), fossil non-avian dinosaurs (n = 27), and modern and fossil mesoeucrocodylians (n = 38), we demonstrate that some aspects of cranial integration are conserved across these taxonomic groups, despite their major differences in cranial form, function, and development. All three groups are highly modular and consistently exhibit high integration within the occipital region. However, there are also substantial divergences in correlation patterns. Birds uniquely exhibit high correlation between the pterygoid and quadrate, components of the cranial kinesis apparatus, whereas the non-avian dinosaur quadrate is more closely associated with the jugal and quadratojugal. Mesoeucrocodylians exhibit a slightly more integrated facial skeleton overall than the other grades. Overall, patterns of trait integration are shown to be stable among archosaurs, which is surprising given the cranial diversity exhibited by the clade. At the same time, evolutionary innovations such as cranial kinesis that reorganize the structure and function of complex traits can result in modifications of trait correlations and modularity.

Relating neuromuscular control to functional anatomy of limb muscles in extant archosaurs.

Electromyography (EMG) is used to understand muscle activity patterns in animals. Understanding how much variation exists in muscle activity patterns in homologous muscles across animal clades during similar behaviours is important for evaluating the evolution of muscle functions and neuromuscular control. We compared muscle activity across a range of archosaurian species and appendicular muscles, including how these EMG patterns varied across ontogeny and phylogeny, to reconstruct the evolutionary history of archosaurian muscle activation during locomotion. EMG electrodes were implanted into the muscles of turkeys, pheasants, quail, guineafowl, emus (three age classes), tinamous and juvenile Nile crocodiles across 13 different appendicular muscles. Subjects walked and ran at a range of speeds both overground and on treadmills during EMG recordings. Anatomically similar muscles such as the lateral gastrocnemius exhibited similar EMG patterns at similar relative speeds across all birds. In the crocodiles, the EMG signals closely matched previously published data for alligators. The timing of lateral gastrocnemius activation was relatively later within a stride cycle for crocodiles compared to birds. This difference may relate to the coordinated knee extension and ankle plantarflexion timing across the swing-stance transition in Crocodylia, unlike in birds where there is knee flexion and ankle dorsiflexion across swing-stance. No significant effects were found across the species for ontogeny, or between treadmill and overground locomotion. Our findings strengthen the inference that some muscle EMG patterns remained conservative throughout Archosauria: for example, digital flexors retained similar stance phase activity and M. pectoralis remained an 'anti-gravity' muscle. However, some avian hindlimb muscles evolved divergent activations in tandem with functional changes such as bipedalism and more crouched postures, especially M. iliotrochantericus caudalis switching from swing to stance phase activity and M. iliofibularis adding a novel stance phase burst of activity.