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Reptiles represent one of the most diverse groups of tetrapod vertebrates. Extant representatives of reptiles include lepidosaurs (lizards), testudines (turtles) and archosaurs (crocodiles and birds). In particular, they show an important locomotor diversity with bipedal, quadrupedal and facultatively bipedal taxa. This diversity is accompanied by substantial microanatomical disparity in the limb bones. Although many studies have highlighted the link between locomotion and bone microstructure, the latter has never been quantitatively studied from an angular perspective. Indeed, some taxa show microanatomical heterogeneity in cross-section. Here we show, using elliptic Fourier transforms and statistical analyses integrating phylogeny, how angular microanatomical parameters measured on reptilian femoral cross-sections, such as angular bone compactness, can be related to locomotion in this clade. Although phylogeny appears to have a significant impact on our results, we show that a functional signal exists. In particular, we show that bipeds and quadrupeds present a craniolateral-caudomedial and dorsoventral deficit in bone compactness, respectively. This reflects cross-sectional eccentricity in these directions that we relate to the forces acting upon the femur in different postural contexts. This work contributes to deciphering the complex interplay between phylogeny, femoral cross-sectional microanatomy and locomotion in reptiles. [ABSTRACT FROM AUTHOR]

Extant amniotes show remarkable postural diversity. Broadly speaking, limbs with erect (strongly adducted, more vertically oriented) posture are found in mammals that are particularly heavy (graviportal) or show good running skills (cursorial), while crouched (highly flexed) limbs are found in taxa with more generalized locomotion. In Reptilia, crocodylians have a "semi‐erect" (somewhat adducted) posture, birds have more crouched limbs and lepidosaurs have sprawling (well‐abducted) limbs. Both synapsids and reptiles underwent a postural transition from sprawling to more erect limbs during the Mesozoic Era. In Reptilia, this postural change is prominent among archosauriforms in the Triassic Period. However, limb posture in many key Triassic taxa remains poorly known. In Synapsida, the chronology of this transition is less clear, and competing hypotheses exist. On land, the limb bones are subject to various stresses related to body support that partly shape their external and internal morphology. Indeed, bone trabeculae (lattice‐like bony struts that form the spongy bone tissue) tend to orient themselves along lines of force. Here, we study the link between femoral posture and the femoral trabecular architecture using phylogenetic generalized least squares. We show that microanatomical parameters measured on bone cubes extracted from the femoral head of a sample of amniote femora depend strongly on body mass, but not on femoral posture or lifestyle. We reconstruct ancestral states of femoral posture and various microanatomical parameters to study the "sprawling‐to‐erect" transition in reptiles and synapsids, and obtain conflicting results. We tentatively infer femoral posture in several hypothetical ancestors using phylogenetic flexible discriminant analysis from maximum likelihood estimates of the microanatomical parameters. In general, the trabecular network of the femoral head is not a good indicator of femoral posture. However, ancestral state reconstruction methods hold great promise for advancing our understanding of the evolution of posture in amniotes. [ABSTRACT FROM AUTHOR]

Salamanders are often used as analogs for early tetrapods in paleontological reconstructions of locomotion. However, concerns have been raised about whether this comparison is justifiable, necessitating comparisons of a broader range of early tetrapods with salamanders. Here, we test whether the osteological morphology of the hindlimb in the early tetrapod (temnospondyl amphibian) Eryops megacephalus could have facilitated the sequence of limb configurations used by salamanders during terrestrial locomotion. To do so, we present a new method that enables the examination of full limb configurations rather than isolated joint poses. Based on this analysis, we conclude that E. megacephalus may indeed have been capable of salamander-like hindlimb kinematics. Our method facilitates the holistic visual comparison of limb configurations between taxa without reliance on the homology of coordinate system definitions, and can thus be applied to facilitate various comparisons between extinct and extant taxa, spanning the diversity of locomotion both past and present. [ABSTRACT FROM AUTHOR]

Background It's critical to identify COVID-19 patients with a higher death risk at early stage to give them better hospitalization or intensive care. However, thus far, none of the machine learning models has been shown to be successful in an independent cohort. We aim to develop a machine learning model which could accurately predict death risk of COVID-19 patients at an early stage in other independent cohorts. Methods We used a cohort containing 4711 patients whose clinical features associated with patient physiological conditions or lab test data associated with inflammation, hepatorenal function, cardiovascular function, and so on to identify key features. To do so, we first developed a novel data preprocessing approach to clean up clinical features and then developed an ensemble machine learning method to identify key features. Results Finally, we identified 14 key clinical features whose combination reached a good predictive performance of area under the receiver operating characteristic curve 0.907. Most importantly, we successfully validated these key features in a large independent cohort containing 15 790 patients. Conclusions Our study shows that 14 key features are robust and useful in predicting the risk of death in patients confirmed SARS-CoV-2 infection at an early stage, and potentially useful in clinical settings to help in making clinical decisions. [ABSTRACT FROM AUTHOR]

The terrestrial slug Arion vulgaris has recently spread across most of Europe, often causing the local extinction of resident populations of Arion ater s.l. The species hybridize, which leads to the prediction of massive introgression of A. ater genes into A. vulgaris. To test this, we used 16 microsatellite markers applied to samples of both species collected around Görlitz, Germany, during the invasion. Amongst A. vulgaris individuals with typical genitalia, an analysis using structure suggested that only 6% were appreciably admixed with local A. ater ; admixture did not increase over the course of the invasion. Amongst the ~4% of slugs with intermediate genitalia, microsatellites confirmed that they were often hybrids, their anatomy correlating with the estimated share of ancestry from each species. The microsatellites also distinguished the three subspecies of A. ater previously recognized on the basis of genital anatomy and mitochondrial DNA. The subspecies were not well mixed spatially, with A. a. ater in wilder places and A. a. rufus never found in the Polish part of the town; nevertheless, hybridization between them was occurring. Unexpectedly, the microsatellites indicated three genetic races amongst A. vulgaris ; these occurred in different districts and are mixing spatially and genetically only slowly. [ABSTRACT FROM AUTHOR]

The terrestrial slug Deroceras invadens has spread across much of the world over the last century. What is there to learn about its origin, colonizations and diversity by comparing barcoding sequences of the mitochondrial gene COI (cytochrome c oxidase subunit I)? Samples from 317 localities covering most of the species' range yielded 87 haplotypes. Higher diversity, the predominance of private haplotypes and geographic structuring all indicate a native range centred on southern Italy, including eastern Sicily. In contrast, central Italy is dominated by one haplotype, although accompanied by both close and more distant relatives; the lack of geographic structuring suggests recent expansion from a restricted distribution within that region. Beyond the Alps, two haplotypes predominate, accompanied by very similar variants; such star-shaped genealogies characterize recent population growth. Also, some rarer haplotypes have been independently introduced. Generally, haplotypes are well mixed here, often co-occurring at a locality. In North America and Australasia, some frequent haplotypes were likely directly introduced from Italy, because they were not found elsewhere in Europe. The rarity or absence in these continents of one or other of the two dominant European haplotypes suggests that import inspections have restricted repeated introductions. A skyline plot detects the recent demographic expansion but also indicates an earlier population decline in the native area. This may explain why the one-dimensional summary statistics F S and R 2 did not signal population growth. A review of 41 other studies that used DNA to analyse invasions of terrestrial molluscs documents considerable diversity in methodology. Studies using genetic data to date recent invasions probably should adjust standard substitution rates upwards. [ABSTRACT FROM AUTHOR]

Saurischian dinosaurs evolved seven orders of magnitude in body mass, as well as a wide diversity of hip joint morphology and locomotor postures. The very largest saurischians possess incongruent bony hip joints, suggesting that large volumes of soft tissues mediated hip articulation. To understand the evolutionary trends and functional relationships between body size and hip anatomy of saurischians, we tested the relationships among discrete and continuous morphological characters using phylogenetically corrected regression. Giant theropods and sauropods convergently evolved highly cartilaginous hip joints by reducing supraacetabular ossifications, a condition unlike that in early dinosauromorphs. However, transitions in femoral and acetabular soft tissues indicate that large sauropods and theropods built their hip joints in fundamentally different ways. In sauropods, the femoral head possesses irregularly rugose subchondral surfaces for thick hyaline cartilage. Hip articulation was achieved primarily using the highly cartilaginous femoral head and the supraacetabular labrum on the acetabular ceiling. In contrast, theropods covered their femoral head and neck with thinner hyaline cartilage and maintained extensive articulation between the fibrocartilaginous femoral neck and the antitrochanter. These findings suggest that the hip joints of giant sauropods were built to sustain large compressive loads, whereas those of giant theropods experienced compression and shear forces. [ABSTRACT FROM AUTHOR]

Abstract: Tetrapods evolved from within the lobe‐finned fishes around 370 Ma. The evolution of limbs from lobe‐fins entailed a major reorganization of the skeletal and muscular anatomy of appendages in early tetrapods. Concurrently, a degree of similarity between pectoral and pelvic appendages also evolved. Here, we compared the anatomy of appendages in extant lobe‐finned fishes (Latimeria and Neoceratodus) and anatomically plesiomorphic amphibians (Ambystoma, Salamandra) and amniotes (Sphenodon) to trace and reconstruct the musculoskeletal changes that took place during the fins‐to‐limbs transition. We quantified the anatomy of appendages using network analysis. First, we built network models—in which nodes represent bones and muscles, and links represent their anatomical connections—and then we measured network parameters related to their anatomical integration, heterogeneity, and modularity. Our results reveal an evolutionary transition toward less integrated, more modular appendages. We interpret this transition as a diversification of muscle functions in tetrapods compared to lobe‐finned fishes. Limbs and lobe‐fins show also a greater similarity between their pectoral and pelvic appendages than ray‐fins do. These findings on extant species provide a basis for future quantitative and comprehensive reconstructions of the anatomy of limbs in early tetrapod fossils, and a way to better understand the fins‐to‐limbs transition. [ABSTRACT FROM AUTHOR]

Five species of Arion slugs were collected repeatedly at a woodland site in southern England and all individuals weighed. Selected samples of these were dissected so as to weigh components of the reproductive tract. The relative weights of the gonad, spermoviduct and albumen gland provided the basis to categorize individuals into adult, subadult or immature classes, or as juvenile if the sum of these weights was below a threshold. This procedure was validated by raising A. subfuscus in captivity and killing at a range of known ages before and after egg laying. In the other species, organ weights from individuals observed to have laid eggs or mated also helped to calibrate the divisions. Such data from two species demonstrated that, following the production of an egg clutch, the albumen gland took days gradually to regrow. There was little evidence of much variation in life cycle from year to year and the broad patterns, although not precise timings, agreed with studies elsewhere. No species produced more than one generation per year and in all there was a season (brief in A. subfuscus) when adults were absent. The life cycles were predominantly annual, although in some species a minority of individuals might take 18 months to mature. The time of year at which individuals matured into adults varied between species: A. intermedius in August and September, A. distinctus mostly in December and January, A. circumscriptus mostly January to April, A. subfuscus April to early October and A. rufus July to September. The largest two species thus dominated in summer, but at other times the species overlapped considerably in size. In four species, individuals maturing later in the season did so at a smaller size; the possible exception was A. intermedius, in which maturation was highly synchronized. The coefficients of variation in adult size were compared against a collection of such data from other terrestrial molluscs. The smallest species, A. intermedius, had disproportionately large hatchlings. [ABSTRACT FROM AUTHOR]

Members of the mammalian family Felidae (extant and extinct cats) are grossly phenotypically similar, but display a 300-fold range in body size, from less than 1 kg to more than 300 kg. In addition to differences in body mass, felid species show dietary and locomotory specializations that correlate to skull and limb osteological measurements, such as shape or cross-sectional area. However, ecological correlates to the axial skeleton are yet untested. Here, we build on previous studies of the biomechanical and morphological evolution of the felid appendicular skeleton by conducting a quantitative analysis of morphology and allometry in the presacral vertebral column across extant cats. Our results demonstrate that vertebral columns of arboreal, scansorial and terrestrial felids significantly differ in morphology, specifically in the lumbar region, while no distinction based on dietary specialization was found. Body size significantly influences vertebral morphology, with clear regionalization of allometry along the vertebral column, suggesting that anterior (cervicals and thoracics) and posterior (lumbar) vertebrae may be independently subjected to distinct selection pressures. [ABSTRACT FROM AUTHOR]

Graviportal taxa show an allometric increase of the cross-sectional area of supportive bones and are assumed to display microanatomical changes associated with an increase in bone mass. This evokes osteosclerosis (i.e. an increase in bone compactness observed in some aquatic amniotes). The present study investigates the changes in bones' microanatomical organization associated with graviportality and how comparable they are with aquatically acquired osteosclerosis aiming to better understand the adaptation of bone to the different associated functional requirements. Bones of graviportal taxa show microanatomical changes that are not solely attributable to allometry. They display a thicker cortex and a proportionally smaller medullary cavity, with a wider transition zone between these domains. This inner cancellous structure may enable to better enhance energy absorption and marrow support. Moreover, the cross-sectional geometric parameters indicate increased resistance to stresses engendered by bending and torsion, as well as compression. Adaptation to a graviportal posture should be taken into consideration when analyzing possibly amphibious taxa with a terrestrial-like morphology. This is particularly important for palaeoecological inferences about large extinct tetrapods that might have been amphibious and, more generally, for the study of early stages of adaptation to an aquatic life in amniotes. [ABSTRACT FROM AUTHOR]

Ariunculus is a genus of terrestrial slugs often treated as a subgenus of Arion. A survey of the literature reveals doubts about many of the described species: only A. speziae and A. isselii are now generally recognized as belonging to Ariunculus. Ariunculus isselii is widespread on Sardinia. We describe its external appearance, mating behaviour and genital anatomy, and interpret the functioning of the genitalia based on specimens killed during copulation or shortly afterwards. Instead of the distinct epiphallus of Arion, there is only a small ampulla, because sperm are pumped out piecemeal to the recipient rather than transferred in a spermatophore. We speculate (in a framework of sexual selection theory) that this may explain why mating lasts 12 h after the initial genital eversion, much longer than in most Arion. The absence of a spermatophore provides grounds for keeping Ariunculus separate from Arion. Similarly to some Arion species, the papilla is inserted into the partner's partially everted bursa trunk; we discuss four different hypotheses for the function of this arrangement. Also as in some Arion species, the oviduct is everted during mating so as to apply a ligula. We provide information on egg laying in captivity and report that the species can self-fertilize. [ABSTRACT FROM AUTHOR]

Over the past century, various modern analogs have been used to infer the evolution of locomotor performance in stem tetrapods and their fish ancestors, with varying success. Here, we conduct a phylogenetic review of these modern analogs, from chondrichthyans to mammals, highlighting the broad spectrum of vertebrate clades and locomotor behaviors. The pros and cons behind utilizing modern analogs for the early stages of the transition from water to land also are discussed. In particular, it is noted that any hypothesis about locomotion not only must be supported by evidence from living animals but must also be consistent with character transformations in the fossil record. A “total-evidence” approach that emphasizes what extinct taxa could not do, rather than focusing on the specifics of how they functioned, is thus recommended. An example of this approach, which investigates mobility of the limb joints in modern semi-aquatic animals and in the Devonian stem tetrapod Ichthyostega, is detailed. We propose that various locomotion behaviors of modern quadrupeds can be ruled out for Ichthyostega, but that forelimb “crutching” motions, as seen in living mudskippers, may have been possible. The potential for movement in other known Devonian stem tetrapods is assessed through an anatomical comparison of limb joint morphology—and associated mobility—with Ichthyostega, and deemed to have been quite similar. [ABSTRACT FROM AUTHOR]

The large slug known as Arion lusitanicus (or A. vulgaris) is an important pest that is spreading through much of Europe. Arion rufus disappears at sites where A. lusitanicus has established strong populations. The finding of morphological intermediates suggests that A. lusitanicus hybridizes with A. rufus, but interspecific mating had not been proved. Considering the marked differences in their genitalia, it has been hard to envisage how mixed couples might transfer sperm. Arion lusitanicus and A. rufus were collected from pure populations near Görlitz, Germany, and used for laboratory mating trials involving either two individuals of A. rufus (henceforth RR), two of A. lusitanicus (LL) or one of each species (mixed). Matings were video recorded and some couples were killed during or after copulation to study spermatophore transfer and genital anatomy during mating. Three mixed pairs copulated. However, mixed pairs were significantly less likely to copulate than either RR or LL pairs (7% vs 52 and 36%). At each stage of mating, the probability of proceeding further was lower in mixed pairs than predicted from rates in RR and LL pairs, but this effect was strongest for yin-yang formation and initiating copulation. One problem was that A. lusitanicus tried to circle after yin-yang formation, whereas A. rufus remained stationary. In this respect, and in the repositioning of its everted oviduct, it was A. lusitanicus that compromised. LL copulations lasted over twice as long as RR copulations, but spermatophore formation took similar times, permitting reciprocal spermatophore exchange in mixed couples even though their copulations ended much earlier than in LL pairs. Our observations of mating behaviour of intraspecific pairs largely agree with previous descriptions of A. rufus, but we discuss some discrepancies between our findings and the fuller descriptions available for A. lusitanicus. [ABSTRACT FROM AUTHOR]

Microfocus CT (micro-CT) is an imaging method that provides three-dimensional digital data sets with comparable resolution to light microscopy. Although it has traditionally been used for non-destructive testing in engineering, aerospace industries and in preclinical animal studies, new applications are rapidly becoming available in the clinical setting including post-mortem fetal imaging and pathological specimen analysis. Printing three-dimensional models from imaging data sets for educational purposes is well established in the medical literature, but typically using low resolution (0.7 mm voxel size) data acquired from CT or MR examinations. With higher resolution imaging (voxel sizes below 1 micron, <0.001 mm) at micro-CT, smaller structures can be better characterised, and data sets post-processed to create accurate anatomical models for review and handling. In this review, we provide examples of how three-dimensional printing of micro-CT imaged specimens can provide insight into craniofacial surgical applications, developmental cardiac anatomy, placental imaging, archaeological remains and high-resolution bone imaging. We conclude with other potential future usages of this emerging technique. [ABSTRACT FROM AUTHOR]