The Role of Locomotory Ancestry on Secondarily Aquatic Transitions

Land-to-sea evolutionary transitions are great transformations where terrestrial amniote clades returned to aquatic environments. These secondarily aquatic amniote clades include charismatic marine mammal and marine reptile groups, as well as countless semi-aquatic forms that modified their terrestrial locomotor anatomy to varying degrees to be suited for swimming via axial and/or appendicular propulsion. The terrestrial ancestors of secondarily aquatic groups would have started off swimming strikingly differently from one another given their evolutionary histories, as inferred by the way modern terrestrial amniotes swim. With such stark locomotor functional differences between reptiles and mammals, we ask if this impacted these transitions. Axial propulsion appears favored by aquatic descendants of terrestrially sprawling quadrupedal reptiles, with exceptions. Appendicular propulsion is more prevalent across the aquatic descendants of ancestrally parasagittal-postured mammals, particularly early transitioning forms. Ancestral terrestrial anatomical differences that precede secondarily aquatic invasions between mammals and reptiles, as well as the distribution of axial and appendicular swimming in secondarily aquatic clades, may indicate that ancestral terrestrial locomotor anatomy played a role, potentially in both constraint and facilitation, in certain aquatic locomotion styles. This perspective of the land-to-sea transition can lead to new avenues of functional, biomechanical, and developmental study of secondarily aquatic transitions.

One-year unplanned readmission after percutaneous coronary intervention in ST-elevation myocardial infarction: rates, causes and predictors

Introduction and aim

Unplanned readmission after percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI) has a significant impact on the healthcare system. Nevertheless, most of the previous literature evaluated readmission within one month only post PCI without assessing the long-term readmission rates and predictors post-PCI. Therefore, we conducted a retrospective observational study to determine the rates, causes, and predictors of readmission post PCI among patients with STEMI over 1-year follow-up.

Methods

We conducted a single-center retrospective observation cohort study. Study population included all patients who were admitted to the hospital with diagnosis of STEMI and underwent PCI during the same admission (index admission) and discharged alive in the period between Jan 1st, 2016 and Sep 30th, 2018. Patients were divided into two groups: those who had one or more unplanned readmission within one year after PCI and those who were not readmitted. Rates and causes of readmission within one year following PCI were reported. Predictors of readmission post-PCI were assessed using multivariate logistic regression and reported as odds ratio (OR) with p<0.05 indicating statistical significance.

Results

A total of 1257 patients were included in our retrospective analysis. Most of the patients were male (95.9%). The mean age of the study population was 51±10. The most frequent culprit vessel was left anterior descending artery (LAD) in 56.3%. The median troponin T upon presentation was 47 ng/L [interquartile range: 171], with 25th percentile of 17 ng/L and 75th percentile of 2197 ng/L. Although around 70% of patients had reduced ejection fraction during the index admission, only 13.4% of the study population had clinical heart failure (HF). The unplanned readmission rate within one year post PCI was 11.5%, with 8.2% due to cardiac readmission while the remaining 3.3% due to non-cardiac causes. The most common cardiac causes for readmission were acute coronary syndrome and HF as shown in Table 1. As demonstrated in Table 2, positive predictors for all-cause readmission within one year after PCI among patients with STEMI were female gender (aOR= 4.14, 95% CI 2.10–8.18; p-value<0.001), chronic kidney disease (aOR= 2.76, 95% CI 1.07–7.08; p-value= 0.035), PCI using more than one stent (aOR= 1.66, 95% CI 1.09–2.55; p-value= 0.019) and clinical HF during index admission (aOR= 2.36, 95% CI 1.49–3.74; p-value<0.001).

Conclusion

The rate of one-year unplanned readmissions after PCI among patients with STEMI was 11.5%, with acute coronary syndrome and HF as most common causes of cardiac readmission. We found that female gender, chronic kidney disease, PCI with more than one stent and clinical HF were associated with a significantly increased likelihood of readmission after PCI among patients with STEMI which may warrant close and frequent follow-up for these populations.

Funding Acknowledgement

Type of funding sources: None.

Mitral regurgitation increases readmission due to heart failure after percutaneous coronary intervention among patients with ST-elevation myocardial infarction: a retrospective data review

Introduction

Post-ST elevation myocardial infarction (STEMI) course can be complicated with mitral regurgitation (MR) which has significant impact on in-patient outcomes and post-discharge course. MR in the setting of STEMI can be due to left ventricular dilatation, papillary muscle rupture or chordal rupture.

Purpose

In this retrospective study, we aimed to evaluate the impact of MR on readmission within one year after percutaneous coronary intervention (PCI) in STEMI patients.

Methods

We conducted a single-center retrospective observation cohort study. We included all patients admitted to the hospital with diagnosis of STEMI, underwent PCI during the same admission (index admission) and discharged alive in the period between Jan 1st, 2016 and Sep 30th, 2018. Factors associated with readmission due to heart failure within 1 year of discharge were evaluated using multivariate logistic regression and results were reported as odds ratio (OR) with p-value <0.05 indicating statistical significance.

Results

A total of 1257 patients were included in our retrospective analysis. The mean age of the study population was 51±10 years. Around 16% (n=206) of the study population had mitral regurgitation (MR) during their admission for STEMI. Among them, 195 patients had newly discovered MR. MR severity was mild in 196 (95%) patients with MR. Unplanned readmission due to cardiac reasons within 1 year of discharge occurred in 103 (8.2%) patients. Among them, 37 (3%) were readmitted due to heart failure. MR was found to increase the likelihood of readmission due to heart failure within one year after PCI among patients with STEMI by three times (aOR=3.13, 95% CI 1.39–7.03; p-value 0.006). As demonstrated in table 1, other positive predictors for readmission due to heart failure were female gender (aOR=3.80, 95% CI 1.22–11.86; p-value 0.021), chronic kidney disease (aOR=4.56, 95% CI 1.22–17.03; p-value 0.024), and clinical heart failure during the index admission (aOR=4.82, 95% CI 1.53–15.15; p-value 0.007). Interestingly, reduced left ventricular ejection fraction was not a significant predictor of heart failure readmission.

Conclusion

Mitral regurgitation is relatively common in STEMI and most frequently presents with mild severity. In our study, MR was found to be a strong predictor for readmission due to heart failure within one year after PCI among patients with STEMI, which may warrant frequent follow-up for these patients and proper initiation of and titration of guideline-directed medical therapy (GDMT).

Funding Acknowledgement

Type of funding sources: None.

Response to Serrano and Chiappe

In the recent study in Current Biology by Pei and colleagues¹, we used two proxies - wing loading and specific lift - to reconstruct powered flight potential across the vaned feathered fossil pennaraptorans. The results recovered multiple origins of powered flight. We respectfully disagree with the criticism raised by Serrano and Chiappe² that wing loading and specific lift, used in sequence, fail to discriminate between powered flight and gliding. We will explain this in reference to our original conservative approach.

Knowledge of Stroke and its Risk Factors among Stroke Survivors: A Hospital Based Study

Significant variations observed in stroke incidence, risk factors and sufferings between high & resource poor countries. Considering lack of study in our country perspective, the study was designed to assess the knowledge of stroke and its risk factors among stroke survivors in Bangladeshi population. This hospital based cross-sectional study was conducted at the Department of Medicine and Department of Neurology in Uttara Adhunik Medical College & Hospital (UAMCH), Dhaka, Bangladesh. Patients aged >18 years who were admitted with stroke (Ischemic and hemorrhagic) were included in the study. Before enrollment informed consent was ensured. Total 50 patients were interviewed and assessed. Separate case record form was used during data collection. Final analysis was done by SPSS 22.00 version software. A 'good' knowledge of stroke was defined by correct answer to ≥4 out of 7 questions about location, cause, risk factor, warning sign, treatment, complication and prevention of stroke. Among 50 stroke survivors, mean age was 58.34±12.90 (SD) years. Male-female ratio was 1.08:1. Overall 78% patients had good knowledge of stroke. Brain was correctly identified as center of stroke by 52% stroke survivors and disturbance of blood supply to brain as a cause of stroke was recognized by 12%. Stress was the most common risk factor identified (50%). At least one warning sign was identified by 76% stroke survivors. Seventy-four percent stroke survivors knew that they have to be taken to nearest health facility and if possible, in hospital where neurological care is available. Only 4% knew about the golden hour of taking the stroke patient. On average knowledge about treatment, complication and prevention of stroke was good. Stroke knowledge was not significantly associated with demographic and socio-economic profile of stroke survivors. More than two thirds of the patients had knowledge regarding stroke and its risk factors but no uniform pattern of knowledge is noticed.

Aerodynamics Show Membrane-Winged Theropods Were a Poor Gliding Dead-end

The bizarre scansoriopterygid theropods Yi and Ambopteryx had skin stretched between elongate fingers that form a potential membranous wing. This wing is thought to have been used in aerial locomotion, but this has never been tested. Using laser-stimulated fluorescence imaging, we re-evaluate their anatomy and perform aerodynamic calculations covering flight potential, other wing-based behaviors, and gliding capabilities. We find that Yi and Ambopteryx were likely arboreal, highly unlikely to have any form of powered flight, and had significant deficiencies in flapping-based locomotion and limited gliding abilities. Our results show that Scansoriopterygidae are not models for the early evolution of bird flight, and their structurally distinct wings differed greatly from contemporaneous paravians, supporting multiple independent origins of flight. We propose that Scansoriopterygidae represents a unique but failed flight architecture of non-avialan theropods and that the evolutionary race to capture vertebrate aerial morphospace in the Middle to Late Jurassic was dynamic and complex.

Volant Fossil Vertebrates: Potential for Bioinspired Flight Technology

Animal flight is ecologically important and has a long evolutionary history. It has evolved independently in many distantly related clades of animals. Powered flight has evolved only three times in vertebrates, making it evolutionarily rare. Major recent fossil discoveries have provided key data on fossil flying vertebrates and critical insights regarding the evolution and different arrangements of animal flight surfaces. Combined with new methodologies, these discoveries have paved the way for potentially expanding biomimetic and biologically inspired designs to incorporate lessons from fossil taxa. Here, we review the latest knowledge and literature regarding flight performance in fossil vertebrates. We then synthesise key elements to provide an overview of those cases where fossil flyers might provide new insights for applied sciences.

The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs

Limb length, cursoriality and speed have long been areas of significant interest in theropod paleobiology, since locomotory capacity, especially running ability, is critical in the pursuit of prey and to avoid becoming prey. The impact of allometry on running ability, and the limiting effect of large body size, are aspects that are traditionally overlooked. Since several different non-avian theropod lineages have each independently evolved body sizes greater than any known terrestrial carnivorous mammal, ~1000kg or more, the effect that such large mass has on movement ability and energetics is an area with significant implications for Mesozoic paleoecology. Here, using expansive datasets that incorporate several different metrics to estimate body size, limb length and running speed, we calculate the effects of allometry on running ability. We test traditional metrics used to evaluate cursoriality in non-avian theropods such as distal limb length, relative hindlimb length, and compare the energetic cost savings of relative hindlimb elongation between members of the Tyrannosauridae and more basal megacarnivores such as Allosauroidea or Ceratosauridae. We find that once the limiting effects of body size increase is incorporated there is no significant correlation to top speed between any of the commonly used metrics, including the newly suggested distal limb index (Tibia + Metatarsus/ Femur length). The data also shows a significant split between large and small bodied theropods in terms of maximizing running potential suggesting two distinct strategies for promoting limb elongation based on the organisms’ size. For small and medium sized theropods increased leg length seems to correlate with a desire to increase top speed while amongst larger taxa it corresponds more closely to energetic efficiency and reducing foraging costs. We also find, using 3D volumetric mass estimates, that the Tyrannosauridae show significant cost of transport savings compared to more basal clades, indicating reduced energy expenditures during foraging and likely reduced need for hunting forays. This suggests that amongst theropods, hindlimb evolution was not dictated by one particular strategy. Amongst smaller bodied taxa the competing pressures of being both a predator and a prey item dominant while larger ones, freed from predation pressure, seek to maximize foraging ability. We also discuss the implications both for interactions amongst specific clades and Mesozoic paleobiology and paleoecological reconstructions as a whole.

New perspectives on the origins of the unique vocal tract of birds

Birds utilize a unique structure, called a syrinx, for the production of their vocalizations. The origins of the syrinx are not well understood. New work, utilizing first principles–based models, suggests that a key element in selection for the early syrinx might be the position of this vocal structure: although the larynx sits at the cranial end of the airway, the avian syrinx is located at the base of the airway at the split of the trachea to the lungs. This position may make the syrinx intrinsically more efficient, which might have been critical in the origin of this anatomical feature.

Birds use a unique structure called a syrinx for producing their calls, but its origins are not well understood. This Primer explores the implications of a new study suggesting that a key element in selection for the early syrinx might its position at the base of the airway, which may make it intrinsically more efficient.

Evidence for the Cretaceous shark Cretoxyrhina mantelli feeding on the pterosaur Pteranodon from the Niobrara Formation

A cervical vertebra of the large, pelagic pterodactyloid pterosaur Pteranodon sp. from the Late Cretaceous Niobrara Formation of Kansas, USA is significant for its association with a tooth from the large lamniform shark, Cretoxyrhina mantelli. Though the tooth does not pierce the vertebral periosteum, the intimate association of the fossils-in which the tooth is wedged below the left prezygapophysis-suggests their preservation together was not mere chance, and the specimen is evidence of Cretoxyrhina biting Pteranodon. It is not possible to infer whether the bite reflects predatory or scavenging behaviour from the preserved material. There are several records of Pteranodon having been consumed by other fish, including other sharks (specifically, the anacoracid Squalicorax kaupi), and multiple records of Cretoxyrhina biting other vertebrates of the Western Interior Seaway, but until now interactions between Cretoxyrhina and Pteranodon have remained elusive. The specimen increases the known interactions between large, pelagic, vertebrate carnivores of the Western Interior Seaway of North America during the Late Cretaceous, in addition to bolstering the relatively small fossil record representing pterosaurian interactions with other species.

The wings before the bird: an evaluation of flapping-based locomotory hypotheses in bird antecedents

BACKGROUND

Powered flight is implicated as a major driver for the success of birds. Here we examine the effectiveness of three hypothesized pathways for the evolution of the flight stroke, the forelimb motion that powers aerial locomotion, in a terrestrial setting across a range of stem and basal avians: flap running, Wing Assisted Incline Running (WAIR), and wing-assisted leaping.

METHODS

Using biomechanical mathematical models based on known aerodynamic principals and in vivo experiments and ground truthed using extant avians we seek to test if an incipient flight stroke may have contributed sufficient force to permit flap running, WAIR, or leaping takeoff along the phylogenetic lineage from Coelurosauria to birds.

RESULTS

None of these behaviours were found to meet the biomechanical threshold requirements before Paraves. Neither was there a continuous trend of refinement for any of these biomechanical performances across phylogeny nor a signal of universal applicability near the origin of birds. None of these flap-based locomotory models appear to have been a major influence on pre-flight character acquisition such as pennaceous feathers, suggesting non-locomotory behaviours, and less stringent locomotory behaviours such as balancing and braking, played a role in the evolution of the maniraptoran wing and nascent flight stroke. We find no support for widespread prevalence of WAIR in non-avian theropods, but can't reject its presence in large winged, small-bodied taxa like Microraptor and Archaeopteryx.

DISCUSSION

Using our first principles approach we find that "near flight" locomotor behaviors are most sensitive to wing area, and that non-locomotory related selection regimes likely expanded wing area well before WAIR and other such behaviors were possible in derived avians. These results suggest that investigations of the drivers for wing expansion and feather elongation in theropods need not be intrinsically linked to locomotory adaptations, and this separation is critical for our understanding of the origin of powered flight and avian evolution.

A specimen of Rhamphorhynchus with soft tissue preservation, stomach contents and a putative coprolite

Despite being known for nearly two centuries, new specimens of the derived non-pterodactyloid pterosaur Rhamphorhynchus continue to be discovered and reveal new information about their anatomy and palaeobiology. Here we describe a specimen held in the collections of the Royal Tyrrell Museum of Palaeontology, Alberta, Canada that shows both preservation and impressions of soft tissues, and also preserves material interpreted as stomach contents of vertebrate remains and, uniquely, a putative coprolite. The specimen also preserves additional evidence for fibers in the uropatagium.

Fossil plotopterid seabirds from the Eo-Oligocene of the Olympic Peninsula (Washington State, USA): descriptions and functional morphology

The plotopterids (Aves, Plotopteridae) were a group of extinct wing-propelled marine birds that are known from Paleogene-aged sediments (Eocene to Miocene), mostly around the Pacific Rim (especially Japan and the northwest coast of North America). While these birds exhibit a strikingly similar wing morphology to penguins (Spheniscidae), they also share derived characters with pelecaniform birds that are absent in penguins and exhibit apparently superficial similarities with auks (Alcidae: Charadriiformes). Despite quite an abundant fossil record, these birds have been little studied, and in particular their functional morphology remains little understood. Here we present osteological overviews of specimens from the northwest coast of Washington state (USA). We give an amended diagnosis for the well-represented North American genus, Tonsala Olson, 1980, describe a new large species, and examine the functional morphology of plotopterids showing that the ratio of humeral strength to femoral strength is quite low in one well-represented species Tonsala buchanani sp.nov., relative to both extant penguins and alcids. While the femoral strength of Tonsala buchanani is 'penguin-grade', its humeral strength is more 'alcid-grade'. These results have implications for understanding the mode-of-locomotion of these extinct marine birds. Although not related to Spheniscidae, our descriptions and functional results suggest that Tonsala buchanani sustained similar loads in walking, but slightly lower humeral loads during swimming, than a modern penguin. This suggests a swimming mode that is more similar to living alcids, than to the highly-specialised locomotor strategy of living and fossil penguins.

On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness

The size and flight mechanics of giant pterosaurs have received considerable research interest for the last century but are confused by conflicting interpretations of pterosaur biology and flight capabilities. Avian biomechanical parameters have often been applied to pterosaurs in such research but, due to considerable differences in avian and pterosaur anatomy, have lead to systematic errors interpreting pterosaur flight mechanics. Such assumptions have lead to assertions that giant pterosaurs were extremely lightweight to facilitate flight or, if more realistic masses are assumed, were flightless. Reappraisal of the proportions, scaling and morphology of giant pterosaur fossils suggests that bird and pterosaur wing structure, gross anatomy and launch kinematics are too different to be considered mechanically interchangeable. Conclusions assuming such interchangeability--including those indicating that giant pterosaurs were flightless--are found to be based on inaccurate and poorly supported assumptions of structural scaling and launch kinematics. Pterosaur bone strength and flap-gliding performance demonstrate that giant pterosaur anatomy was capable of generating sufficient lift and thrust for powered flight as well as resisting flight loading stresses. The retention of flight characteristics across giant pterosaur skeletons and their considerable robustness compared to similarly-massed terrestrial animals suggest that giant pterosaurs were not flightless. Moreover, the term 'giant pterosaur' includes at least two radically different forms with very distinct palaeoecological signatures and, accordingly, all but the most basic sweeping conclusions about giant pterosaur flight should be treated with caution. Reappraisal of giant pterosaur material also reveals that the size of the largest pterosaurs, previously suggested to have wingspans up to 13 m and masses up to 544 kg, have been overestimated. Scaling of fragmentary giant pterosaur remains have been misled by distorted fossils or used inappropriate scaling techniques, indicating that 10-11 m wingspans and masses of 200-250 kg are the most reliable upper estimates of known pterosaur size.