Radial Pattern Research Articles

Joint inversion of tectonic stress and magma pressures using dyke trajectories

AbstractIn volcano-tectonic regions, dyke propagation from shallow magmatic chambers is often controlled by the interaction of the local and regional stress fields. The variations of the stress fields result from a combination of factors including the regional tectonic stress, the geometry of pressurized magma chambers, the layering and the pre-existing discontinuities (e.g. fractures). In this contribution, we describe and apply a new multiparametric inversion technique based on geomechanics that can invert for both the far field stress attributes and the internal pressure of magma chambers or stocks, constrained by observed dyke or eruptive fissure orientations. This technique is based on the superposition principle and uses linear elastic models that can be solved using many types of numerical methods. For practical reasons, we chose a 3D boundary element method (BEM) for a heterogeneous elastic half-space, where magma chambers are modelled as pressurized cavities. To verify this approach, the BEM solution has been validated against the known 3D analytical solution of a pressurized cylindrical cavity. Then the effectiveness of this technique and its practical use is demonstrated through application to natural examples of dyke network development around two different volcanic systems, the Spanish Peaks (USA) and the Galapagos Islands (Ecuador). Results demonstrate that regional stress characteristics as well as the internal pressure of magma chambers can be estimated from observed radial and circumferential dyke patterns and some knowledge of magma chamber geometry.

Rhythmic Spatial Self-Organization of Bacterial Colonies.

ABSTRACTBacteria display a remarkable capacity to organize themselves in space and time within biofilms. Traditionally, the spatial organization of biofilms has been dissected vertically; however, biofilms can exhibit complex, temporally structured, two-dimensional radial patterns while spreading on a surface. Kahl and colleagues report a ring pattern that indicates the alternating redox metabolism of P. aeruginosa biofilms under light/dark cycles. Does the presence of a rhythmic, daily phenotype imply a circadian rhythm? Here, we highlight several examples of rhythmic patterns reported in the literature for surface-colonizing multicellular assemblies and discuss the conceptual requirements for proving the presence of a prokaryotic circadian clock behind pattern formation.

Flow distribution in the liquid film created by a coherent circular water jet impinging obliquely on a plane wall

When a coherent liquid jet impinges normally on a flat wall, the liquid flows away from the point of impingement in a radial pattern. The effect of the angle of impingement on the distribution of the flow in the azimuthal direction on a vertical polymethylmethacrylate wall was studied for angles of impingement ranging from 35.3° to 144.7°. The flow distribution was calculated from measurements of the location of the hydraulic jump and the rate of growth of the area cleaned of a soft solid soil layer (moisturising cream), for water jets generated from a 2 mm circular nozzle with Reynolds numbers ranging from 10,600–31,800. Distributions based on the initial location of the jump (before a draining film was established) agreed well with those calculated from cleaning tests, and were compared with three models based on geometric constructions as well as the ideal case derived assuming no dissipation presented by Hasson and Peck (AIChE J, 1964, 10, 752). The latter consistently overpredicted the fraction of flow in the principal direction and underpredicted the flow in the backwards direction. The changing ellipse model (CEM) gave the best description of the experimental data presented here as well as some results reported by other workers, but not for others. The results indicate that a priori estimates of flow distribution require detailed numerical calculations: the CEM can be used in short-cut calculations following calibration.

Distributed encoding of curvilinear self-motion across spiral optic flow patterns

Self-motion along linear paths without eye movements creates optic flow that radiates from the direction of travel (heading). Optic flow-sensitive neurons in primate brain area MSTd have been linked to linear heading perception, but the neural basis of more general curvilinear self-motion perception is unknown. The optic flow in this case is more complex and depends on the gaze direction and curvature of the path. We investigated the extent to which signals decoded from a neural model of MSTd predict the observer’s curvilinear self-motion. Specifically, we considered the contributions of MSTd-like units that were tuned to radial, spiral, and concentric optic flow patterns in “spiral space”. Self-motion estimates decoded from units tuned to the full set of spiral space patterns were substantially more accurate and precise than those decoded from units tuned to radial expansion. Decoding only from units tuned to spiral subtypes closely approximated the performance of the full model. Only the full decoding model could account for human judgments when path curvature and gaze covaried in self-motion stimuli. The most predictive units exhibited bias in center-of-motion tuning toward the periphery, consistent with neurophysiology and prior modeling. Together, findings support a distributed encoding of curvilinear self-motion across spiral space.

Assessing the effect of environmental and socio-economic factors on skin melanoma incidence: an island-wide spatial study in Gran Canaria (Spain), 2007–2018

IntroductionSkin melanoma incidence has risen in the last decades becoming a major public health problem in many regions of the world. Geographic variation of rates is not well understood.PurposeTo assess the spatial distribution of skin melanoma in Gran Canaria Island (Canary Islands, Spain) and to evaluate the role of environmental, socio-economic, and demographic factors in this distribution.MethodsWe performed a small-area study with disease mapping at the census-tract level (CT) in Gran Canaria between 2007 and 2018. After testing for spatial autocorrelation, we integrated individual-level health data with census-based demographic and socio-economic indicators, and satellite-based environmental data. Finally, we assessed the role of demographic, socio-economic and environmental factors on skin melanoma incidence using a Bayesian analytical framework, with options for non-spatial and spatial random effects.Results1058 patients were diagnosed with invasive skin melanoma in the study period and geolocated to a CT (number of CT in Gran Canaria = 565). We found evidence of global spatial autocorrelation in skin melanoma incidence (Moran’s I = 0.09, pseudo p-value = 0.001). A few hotspots were detected, fundamentally in urban northern tracts. A radial pattern of high values was also observed in selected ravines with historical isolation. Multivariable conditional autoregressive models identified urbanicity, percent of females, and a high socio-economic status as risk factors for disease. Solar radiation did not show a significant role.ConclusionUrbanicity and a high socio-economic status were identified as the main risk factors for skin melanoma. These associations might reflect differential melanoma susceptibilities or be explained by health inequalities in detection. This study also uncovered high-risk areas in particular ravines. Future targeted research in these regions might help better understand the role of genetic and toxic factors in melanoma pathogenesis.

Sampling patterns may influence the evaluation of irrigation uniformity of Center Pivot systems

Abstract The evaluation of irrigation uniformity can be affected by the sampling pattern in the field. Thus, this work aimed to compare the water application uniformities of a Center Pivot using three sampling patterns: along the equipment radius (radial), in the direction of movement of the pivot (circular) and in a two-dimensional way (meshed). For this, samplers were positioned under the spans of a Center Pivot system, being evaluated the effects of the sampling pattern and of the span, in a 3×3 statistical factorial design, with three replications. The results showed that circular and meshed arrangements were statistically equal and had higher values of Christiansen's and Distribution Uniformity Coefficients. The mesh type arrangement represented a more uniform distribution profile of irrigation depths on the surface. For areas of flat or slightly undulating topography and when using pressure regulating valves for the emitters, sampling in a radial pattern is sufficient, but for terrains with irregular topography or when pressure head variations along the lateral line are important for the operation of the emitters, the combination of the radial and circular pattern is interesting. The meshed sampling detects the stoppage effect of the towers and drift, however, in a reduced area.

Clinical course and treatment of archipelago keratitis: a Herpesviridae keratitis subtype

PurposeArchipelago keratitis (ApK) is a subtype of Herpesviridae stromal keratitis that consists of subepithelial nummular inflammatory infiltrates arranged in a radial centripetal pattern. This rare and poorly described form is...

Reduced Rainfall Variability Reduces Growth of Nothofagus alessandrii Espinosa (Nothofagaceae) in the Maule Region, Chile

Nothofagus alessandrii Espinosa is an endemic species of the coastal Maulino forest of central Chile that has historically been severely threatened by the reduction of its habitat and the isolation of its fragments. In addition, a gradual reduction in precipitation has been observed in recent years across its entire natural distribution area. Although the genus Nothofagus has been extensively analyzed in dendrochronological studies in the Southern Hemisphere, the dendrochronological potential of this species is unknown. In this study, we developed a novel tree-ring chronology of N. alessandrii in order to examine the climate sensitivity of the radial growth and to thus understand its response to climate change in central Chile. Our ring-width chronology showed a series intercorrelation value of 0.48 for the period of 1942–2016 (EPS < 0.85, with 10 trees), showing a strong common growth signal among the trees. N. alessandrii growth was strongly influenced by precipitation from May to November (the austral winter and spring seasons), while the temperature signal was weak. We observed that the radial growth patterns of N. alessandrii chronology showed upward growth trends, with a marked positive slope until the mid-1980s. However, a negative trend was observed for the period of 1985–2016, which was related to the increased drought conditions (rainfall and soil moisture reductions) in past decades and affected the entire natural distribution of the species. We suggest that drier winters and springs would slow the growth of this species. This information is of vital importance to understanding the growth dynamics of N. alessandrii, a critically endangered species, and to take on urgent adaptation and mitigation measures in the face of climate change.

Forgetting in visual working memory: Internal noise explains decay of feature representations.

The precision of visual working memory (VWM) representations decreases as time passes. It is often assumed that VWM decay is random and caused by internal noise accumulation. However, forgetting in VWM could occur systematically, such that some features deteriorate more rapidly than others. There exist only a few studies testing these two models of forgetting, with conflicting results. Here, decay of features in VWM was thoroughly tested using signal detection theory methods: psychophysical classification images, internal noise estimation, and receiver operant characteristic (ROC). A modified same–different memory task was employed with two retention times (500 and 4000 ms). Experiment 1 investigated VWM decay using a compound grating memory task, and Experiment 2 tested shape memory using radial frequency patterns. Memory performance dropped some 15% with increasing retention time in both experiments. Interestingly, classification images showed virtually indistinguishable weighting of stimulus features at both retention times, suggesting that VWM decay is not feature specific. Instead, we found a 77% increase in stimulus-independent internal noise at the longer retention time. Finally, the slope of the ROC curve plotted as z-scores was shallower at the longer retention time, indicating that the amount of stimulus-independent internal noise increased. Together these findings provide strong support for the idea that VWM decay does not result from a systematic loss of some stimulus features but instead is caused by uniformly increasing random internal noise.

Effectiveness of controlling COVID-19 epidemic by implementing soft lockdown policy and extensive community screening in Taiwan

Strict and repeated lockdowns have caused public fatigue regarding policy compliance and had a large impact on several countries’ economies. We aimed to evaluate the effectiveness of a soft lockdown policy and the strategy of active community screening for controlling COVID-19 in Taiwan. We used village-based daily confirmed COVID-19 statistics in Taipei City and New Taipei City, between May 2, 2021, and July 17, 2021. The temporal Gi* statistic was used to compute the spatiotemporal hotspots. Simple linear regression was used to evaluate the trend of the epidemic, positivity rate from community screening, and mobility changes in COVID-19 cases and incidence before and after a level three alert in both cities. We used a Bayesian hierarchical zero-inflated Poisson model to estimate the daily infection risk. The cities accounted for 11,403 (81.17%) of 14,048 locally confirmed cases. The mean effective reproduction number (Re) surged before the level three alert and peaked on May 16, 2021, the day after the level three alert in Taipei City (Re = 3.66) and New Taipei City (Re = 3.37). Mobility reduction and a lower positive rate were positively associated with a lower number of cases and incidence. In the spatiotemporal view, seven major districts were identified with a radial spreading pattern from one hard-hit district. Villages with a higher inflow degree centrality among people aged ≥ 60 years, having confirmed cases, specific land-use types, and with a higher aging index had higher infection risks than other villages. Early soft lockdown policy and detection of infected patients showed an effective strategy to control COVID-19 in Taiwan.

Formation of Titanium Oxide on Nonmetal Substrates and the Coordination Structure of Titanium Ions in Molten Lif-KF

Electrodeposition of titanium materials on substrates is an important technique to improve and functionalize the surface properties. Especially electrodeposition of titanium and titanium oxide on a material that is an insulator. However, electrodeposition of an insulator on another insulator is considered to be difficult. If such deposition can be accomplished, it would have a variety of practical applications in both mechanical and electronic industries. We are thus proposing a new method for electrodeposition of titanium oxide on alumina substrates in LiF-KF with the addition of TiO2 and metal titanium. We have carried out the electrodeposition to test hypotheses on deposition of titanium oxide on the alumina surface by employing the three electrodes method in the molten salt. The nickel-wire in contact with alumina substrate was employed as a working electrode to grow titanium oxide on the substrate by the proposed electrochemical process. Titanium oxide deposition grew from the three-phase interface of nickel wire, molten salt and alumina substrate in a radial pattern. The growth rate of the deposition was controlled by adjusting the electrochemical parameters. We have also investigated the melt structure of LiF-KF with the addition of TiO2 and the addition of bulk titanium by combining high temperature Raman spectroscopic technique and density functional theory calculations. These results provide new insight into the growth process of titanium oxide crystals and possibly a new comprehensive plating procedure for titanium oxide on insulator substrates.

Developmental changes in gaze patterns in response to radial optic flow in toddlerhood and childhood

A large field visual motion pattern (optic flow) with a radial pattern provides a compelling perception of self-motion; a radially expanding/contracting optic flow generates the perception of forward/backward locomotion. Moreover, the focus of a radial optic flow, particularly an expansive flow, is an important visual cue to perceive and control the heading direction during human locomotion. Previous research has shown that human gaze patterns have an “expansion bias”: a tendency to be more attracted to the focus of expansive flow than to the focus of contractive flow. We investigated the development of the expansion bias in children (N = 240, 1–12 years) and adults (N = 20). Most children aged ≥ 5 years and adults showed a significant tendency to shift their gaze to the focus of an expansive flow, whereas the youngest group (1-year-old children) showed a significant but opposing tendency; their gaze was more attracted to the focus of contractive flow than to the focus of expansive flow. The relationship between the developmental change from the “contraction bias” in early toddlerhood to the expansion bias in the later developmental stages and possible factors (e.g., global visual motion processing abilities and locomotor experiences) are discussed.

Chemo-kinematics of the Milky Way spiral arms and bar resonances: Connection to ridges and moving groups in the solar vicinity

Making use of a new high-resolution spiral galaxy simulation as well as Gaia DR2 and EDR3 data complemented by chemical abundances from the Galah DR3, APOGEE DR16, and LAMOST DR5 surveys, we explore the possible link between the Milky Way (MW) spiral arms, (R, vϕ) ridges, and moving groups in local vR-vϕ space. We show that the tightly wound main spiral arms in the N-body simulation can be successfully identified using overdensities in angular momentum (AM) or guiding space and also in the distribution of dynamically cold stars close to their guiding centres. Stars in the AM overdensities that travel over many kiloparsec in radius trace extended density ridges in (R, vϕ) space and overdensities in the vR-vϕ plane of a solar neighbourhood (SNd)-like region, similar to those observed in the Gaia data. Similarly, the AM space of the MW contains several overdensities that correlate with a wave-like radial velocity pattern; this pattern is also reproduced by stars well beyond the SNd. We find that the fraction of Gaia stars located near their guiding centres shows three large-scale structures that approximately coincide with the MW spiral arms traced by distributions of maser sources in the Sagittarius, Local, and Perseus arms. This approach does not work for the Scutum arm near the end of the bar. Similar to the simulation, the stars in the AM overdensities follow the main (R, vϕ) density ridges with nearly constant angular momentum. When these ridges cross the SNd, they can be matched with the main vR-vϕ features. Thus we suggest that the Hat is the inner tail of the Perseus arm, one of the Hercules components is the Sagittarius arm, and the Arcturus stream is likely to be the outermost tail of the Scutum-Centaurus arm. Based on previous work, the bar corotation is suggested to coincide with the second, vϕ ≈ −55 km s−1 Hercules stream ridge, and the OLR with the Sirius stream. The latter is supported by a sharp decrease in mean metallicity beyond the Sirius stream, which is an expected behaviour of the OLR, limiting migration of the metal-rich stars from the inner MW. In various phase-space coordinates, the AM overdensity stars have a mean metallicity that is systematically higher by about 0.05 dex than the metallicity of the surrounding stars. This is a predicted behaviour of the spiral arms. We show that the wave-like metallicity pattern can be traced at least up to |z|≈1 kpc. It is linked to radial velocity variations seen even farther (|z|≈2 kpc) from the Galactic mid-plane.

The Use of Feature Tracking Technique for the Quantification of Ventricular Strain Pattern in Patients with Ebstein's Anomaly: A Case-Control Study.

Background: Ebstein’s anomaly (EA) is a congenital heart disorder characterized by abnormal function of the tricuspid valve. There are several ways to study tissue composition using magnetic resonance imaging (MRI). One of the most accurate methods is strain calculation using the feature tracking (FT) technique. Due to the novelty of the FT technique in cardiac magnetic resonance (CMR) imaging, there is a lack of comprehensive guidelines to conduct FT-MRI and to present a quantitative report. The current study is aimed to evaluate the FT technique in EA patients and to compare the obtained numerical values with those of healthy individuals.Methods: A total of 33 individuals were enrolled in a study conducted in 2018-2019 at Shahid Rajaei Hospital, Tehran, Iran. Radial, longitudinal, and circumferential strain patterns of the left and right ventricles were determined in both the patients and the controls using the FT technique. Data were analyzed using SPSS software, version 22.0.Results: The results showed a significantly lower left ventricular (LV) radial strain in EA patients compared to the control group (P=0.002). In addition, the right ventricular (RV) global longitudinal strain (GLS) in EA patients was significantly lower than in the controls (P=0.001). Other parameters (LV global longitudinal strain, RV radial strain, LV circumferential strain, and RV circumferential strain) did not differ significantly between the two groups.Conclusion: Determination of strain patterns using cardiac MRI is a promising method for the diagnosis of EA. Markers such as LV longitudinal strain and RV-GLS are the most suitable parameters for the early diagnosis of heart dysfunction.

Vis-NIR hyperspectral imaging combined with incremental learning for open world maize seed varieties identification

There are many maize seed varieties circulating on the Chinese market, some varieties will be added and eliminated by the government every year, and fake varieties cannot be exhaustively listed. Furthermore, the updating of some varieties requires retraining the entire model, which is time-consuming and laborious. This poses a huge challenge for the authenticity identification of varieties and online model updating. Herein, hyperspectral imaging (HSI) combined with incremental learning (IL) was used to solve this problem. A novel radial basis function-biomimetic pattern recognition (RBF-BPR) model for IL was proposed and compared with one-class support vector machine (OCSVM) and BPR models under two test schemes. Hyperspectral images of five varieties of maize seeds were collected, and convolutional autoencoder (CAE) was used to extract features to remove redundant information and improve the generalization ability of models. A unique hybrid model was designed for each variety respectively, and the IL process was simulated. In two test schemes, the overall correct acceptance rate (CAR) for the known varieties and the overall correct rejection rate (CRR) for the unknown varieties of CAE-RBF-BPR model both reached 100%, which was superior to CAE-OCSVM and CAE-BPR models. Especially after RBF was used to map data, the performance of RBF-BPR model had a qualitative improvement compared with the original BPR model. In summary, the proposed method can realize IL without accessing the old classes data, while meeting the requirements of identifying known varieties and rejecting unknown varieties. In addition, if some varieties are eliminated by the government in the future, the corresponding models can also be removed form the whole system. The combination of such method and HSI has a broad application prospect in the identification of maize seed varieties, thus avoiding the trouble of retraining entire model when some maize seed varieties need to be updated.

Eyewall asymmetries and their contributions to the intensification of an idealized tropical cyclone translating in uniform flow

Abstract Scale-dependent processes within the tropical cyclone (TC) eyewall and their contributions to intensification are examined in an idealized simulation of a TC translating in uniform environmental flow. The TC circulation is partitioned into axisymmetric, low-wavenumber (m = 1–3), and high-wavenumber (m > 3) categories, and scale-dependent contributions to the intensification process are quantified through the azimuthal-mean relative (vertical) vorticity and tangential momentum budgets. To further account for the interdependent relationship between the axisymmetric vortex structure and eyewall asymmetries, the analyses are subdivided into three periods—early, middle, and late—that represent the approximate quartiles of the full intensification period prior to the TC attaining its maximum intensity. The asymmetries become concentrated among lower azimuthal wavenumbers during the intensification process and are persistently distributed among a broader range of azimuthal scales at higher altitudes. The scale-dependent budgets demonstrate that the axisymmetric and asymmetric processes generally oppose each other during TC intensification. The axisymmetric processes are mostly characterized by a radial spin-up dipole pattern, with a tangential momentum spin-up tendency concentrated along the radius of maximum tangential winds (RMW) and a spin-down tendency concentrated radially inward of the RMW. The asymmetric processes are mostly characterized by an opposing spin-down dipole pattern that is slightly weaker in magnitude. The most salient exception occurs from high-wavenumber processes contributing to a relatively modest, net spin-up along the RMW between ~2–4 km altitude. Given that the maximum tangential winds persistently reside below 2-km altitude, eyewall asymmetries are primarily found to impede TC intensification.

Estimating curvilinear self-motion from optic flow with a biologically inspired neural system* *This work was supported by The Office of Naval Research ONR N00014-18-1-2283.

Optic flow provides rich information about world-relative self-motion and is used by many animals to guide movement. For example, self-motion along linear, straight paths without eye movements, generates optic flow that radiates from a singularity that specifies the direction of travel (heading). Many neural models of optic flow processing contain heading detectors that are tuned to the position of the singularity, the design of which is informed by brain area MSTd of primate visual cortex that has been linked to heading perception. Such biologically inspired models could be useful for efficient self-motion estimation in robots, but existing systems are tailored to the limited scenario of linear self-motion and neglect sensitivity to self-motion along more natural curvilinear paths. The observer in this case experiences more complex motion patterns, the appearance of which depends on the radius of the curved path (path curvature) and the direction of gaze. Indeed, MSTd neurons have been shown to exhibit tuning to optic flow patterns other than radial expansion, a property that is rarely captured in neural models. We investigated in a computational model whether a population of MSTd-like sensors tuned to radial, spiral, ground, and other optic flow patterns could support the accurate estimation of parameters describing both linear and curvilinear self-motion. We used deep learning to decode self-motion parameters from the signals produced by the diverse population of MSTd-like units. We demonstrate that this system is capable of accurately estimating curvilinear path curvature, clockwise/counterclockwise sign, and gaze direction relative to the path tangent in both synthetic and naturalistic videos of simulated self-motion. Estimates remained stable over time while rapidly adapting to dynamic changes in the observer’s curvilinear self-motion. Our results show that coupled biologically inspired and artificial neural network systems hold promise as a solution for robust vision-based self-motion estimation in robots.

Distribution and Morphology of Lava Tube Systems on the Western Flank of Alba Mons, Mars

AbstractIntegrated analyses of Thermal Emission Imaging System (THEMIS) IR, Context Camera (CTX), and Mars Orbiter Laser Altimeter (MOLA) data sets have been used to characterize the western flank of the Martian volcano Alba Mons, which hosts a prominent population of lava tube systems. Identification and mapping of lava tube systems is based on both morphologic and topographic analyses, including the presence of chains of collapse depressions and elongate, sinuous ridges. Lava tubes and adjacent tabular lava flows with lengths of 100+ km form an extensive lava flow field. Analyses of topographic data sets, including slope maps, suggest continuity of the radial flow field pattern across the full western flank. Concurrent surface activity across the western flank is consistent with age constraints from geologic mapping and crater size‐frequency distributions that indicate Early Amazonian ages. The mapped population of 331 lava tube systems in the western flank geologic map quadrangle has a mean length of 36.2 km and a total length of ∼12,000 km. Individual lava tube systems extend up to ∼400 km. Orientation and slope data for lava tube systems show small deviations compared to regional values in 50‐km grid cells defined by the MOLA Digital Elevation Model, suggesting a strong coupling of lava tubes to the current slopes of Alba Mons. Mapping of lava tube systems documents segments both showing collapse and with no collapse, indicating the potential for extensive subsurface cavities that would be important astrobiological targets.

Inter-annual and inter-species tree growth explained by phenology of xylogenesis.

Summary Wood formation determines major long‐term carbon (C) accumulation in trees and therefore provides a crucial ecosystem service in mitigating climate change. Nevertheless, we lack understanding of how species with contrasting wood anatomical types differ with respect to phenology and environmental controls on wood formation.In this study, we investigated the seasonality and rates of radial growth and their relationships with climatic factors, and the seasonal variations of stem nonstructural carbohydrates (NSC) in three species with contrasting wood anatomical types (red oak: ring‐porous; red maple: diffuse‐porous; white pine: coniferous) in a temperate mixed forest during 2017–2019.We found that the high ring width variability observed in both red oak and red maple was caused more by changes in growth duration than growth rate. Seasonal radial growth patterns did not vary following transient environmental factors for all three species. Both angiosperm species showed higher concentrations and lower inter‐annual fluctuations of NSC than the coniferous species.Inter‐annual variability of ring width varied by species with contrasting wood anatomical types. Due to the high dependence of annual ring width on growth duration, our study highlights the critical importance of xylem formation phenology for understanding and modelling the dynamics of wood formation.

Phylogenetic affinities of the poorly known bivalve genus Xenocardita Vokes, 1946 (Bivalvia: Carditidae): new data on the evolution of the tripartite radial ribs

The Mesozoic record of the Carditidae is sparse and poorly known, and the genus Xenocardita constitutes a significant record on account of its early Aptian age, but lacks a proper phylogenetic placement within the family. Based on new observations of specimens and a revision of external sculpture characters, we perform a phylogenetic analysis of the Carditidae including all subfamilies and lineages, with a total of 72 species as ingroup and 153 morphological characters of the shell. Our results show Xenocardita to belong to the tribe Venericardiini (formerly known as ‘alticostate’ carditids). In most runs, Xenocardita is recovered as an early diverging Venericardiini, sister taxon of all remaining members. In consequence, the origin of the clade is moved downwards from the Campanian–Maastrichtian to at least the lower Aptian. The new phylogenetic position of Xenocardita and the re-evaluation of the morphology of the radial ribs, now recognized in this taxon, move the first record of the tripartite radial rib pattern back in time and re-write its evolutionary history. Tripartite radial rib pattern begins with a central cord sided by little pronounced slopes during Early Cretaceous and becomes strongly marked with pronounced paracostal ribs in the Late Cretaceous (represented by the ‘Baluchicardia’ Clade), and survives toward the Miocene, but experiences simplifications in some lineages. A second Cenozoic tripartite pattern appears in the Eocene with strongly pronounced slopes (represented by the ‘Venericardia’ Clade). Other Cretaceous taxa and their possible relationships with the Venericardiini are also discussed.