Osteon shape variation in the femoral diaphysis: A geometric-morphometric approach on human cortical bone microstructure in an elderly sample.

Geometric morphometrics (GMM) have been applied to understand morphological variation in biological structures. However, research studying cortical bone through geometric histomorphometrics (GHMM) is scarce. This research aims to develop a landmark-based GHMM protocol to depict osteonal shape variation in the femoral diaphysis, exploring the role of age and biomechanics in bone microstructure. Proximal, midshaft, and distal anatomical segments from the femoral diaphysis of six individuals were assessed, with 864 secondary intact osteons from eight periosteal sampling areas being manually landmarked. Observer error was tested using Procrustes ANOVA. Average osteonal shape and anatomical segment-specific variation were explored using principal component analysis. Osteon shape differences between segments were examined using canonical variate analysis (CVA). Sex differences were assessed through Procrustes ANOVA and discriminant function analysis (DFA). The impact of osteonal size on osteonal shape was investigated. High repeatability and reproducibility in osteon shape landmarking were reported. The average osteon shape captured was an elliptical structure, with PC1 reflecting more circular osteons. Significant differences in osteon shape were observed between proximal and distal segments according to CVA. Osteon shape differed between males and females, with DFA showing 52% cross-validation accuracies. No effect of size on shape was reported. Osteonal shape variation observed in this study might be explained by the elderly nature of the sample as well as biomechanical and physiological mechanisms playing different roles along the femoral diaphysis. Although a larger sample is needed to corroborate these findings, this study contributes to the best of our knowledge on human microanatomy, proposing a novel GHMM approach.

Bill shape variation in selected species in birds of prey.

At the top of many ecosystems, raptors, also known as birds of prey, hold major influence. They shape their surroundings through their powerful hunting skills and complex interactions with their environment. This study investigates the beak morphology of four prominent raptor species, Golden eagle (Aquila chrysaetos), Common buzzard (Buteo buteo), Peregrine falcon (Falco peregrinus) and Common kestrel (Falco tinnunculus), found in Türkiye. By employing geometric morphometric methods, we investigate shape variations in the beaks of these species to unravel the adaptive significance of their cranial structures. This analysis reveals distinct beak morphologies among the studied raptors, reflecting adaptations to their feeding habits, hunting techniques and ecological niches. The results from Principal component analysis and Canonical variate analysis demonstrate significant differences in beak morphology between the Falconiformes and Accipitriformes clades, as well as among all three groups. The overall mean beak shapes of Golden Eagles are quite similar to Common Buzzards, with both species having longer beaks. In contrast, Falcons exhibit a distinctly different beak morphology, characterized by wider and shorter beaks. Changes in beak shape can lead to changes depending on the skull. It is thought that skull shape variations among predator families may have an impact on beak shape. These findings highlight the importance of integrating morphometric analyses with ecological insights to enhance our understanding of the evolutionary processes shaping raptor beak morphology.

Genetic identification, morphology and distribution of Natrixhelvetica subspecies in southern and western Switzerland (Reptilia, Squamata, Serpentes).

Most of Switzerland is inhabited by the nominotypical subspecies of the barred grass snake (Natrixhelveticahelvetica), which is characterized by mitochondrial DNA lineage E. Only in the northeast of the country, the common grass snake (N.natrix) occurs and hybridizes with N.h.helvetica in a narrow contact zone. However, we discovered that in southern and western Switzerland barred grass snakes representing another mtDNA lineage (lineage C) are widely distributed. Lineage C is typical for Alpine populations of the southern subspecies N.h.sicula. Our microsatellite analyses of the Swiss samples revealed differences between the two subspecies and also a substructure with two clusters in each subspecies. Furthermore, we discovered a contact and hybrid zone of N.h.helvetica and N.h.sicula along the northern shore of Lake Geneva and also confirm that interbreeding with alien common grass snakes (N.n.moreotica, mtDNA lineage 7) occurs there. This finding is of concern for nature conservation and measures should be taken to prevent further genetic pollution. Using morphometrics, we found no differences between the two subspecies of N.helvetica, while N.natrix was slightly distinct from N.helvetica.

Eco-geographic and sexual variation of the ribcage in Homo sapiens.

Up to now, Allen and Bergmann's rules have been studied in modern humans by analyzing differences in limb length, height, or body mass. However, there are no publications studying the effects of latitude in the 3D configuration of the ribcage. To assess this issue, we digitally reconstructed the ribcages of a balanced sample of 109 adult individuals of global distribution. Shape and size of the ribcage was quantified using geometric morphometrics. Our results show that the ribcage belonging to tropical individuals is smaller and slenderer compared to others living in higher latitudes, which is in line with Allen and Bergmann's rules and suggests an allometric relationship between size and shape. Although sexual dimorphism was observed in the whole sample, significant differences were only found in tropical populations. Our proposal is that, apart from potential sexual selection, avoiding heat loss might be the limiting factor for sexual dimorphism in cold-adapted populations.

Functional data geometric morphometrics with machine learning for craniodental shape classification in shrews.

This work proposes a functional data analysis approach for morphometrics in classifying three shrew species (S. murinus, C. monticola, and C. malayana) from Peninsular Malaysia. Functional data geometric morphometrics (FDGM) for 2D landmark data is introduced and its performance is compared with classical geometric morphometrics (GM). The FDGM approach converts 2D landmark data into continuous curves, which are then represented as linear combinations of basis functions. The landmark data was obtained from 89 crania of shrew specimens based on three craniodental views (dorsal, jaw, and lateral). Principal component analysis and linear discriminant analysis were applied to both GM and FDGM methods to classify the three shrew species. This study also compared four machine learning approaches (naïve Bayes, support vector machine, random forest, and generalised linear model) using predicted PC scores obtained from both methods (a combination of all three craniodental views and individual views). The analyses favoured FDGM and the dorsal view was the best view for distinguishing the three species.

Beyond CREA: Evolutionary patterns of non-allometric shape variation and divergence in a highly allometric clade of murine rodents.

The shared functions of the skull are thought to result in common evolutionary patterns in mammalian cranial shape. Craniofacial evolutionary allometry (CREA) is a particularly prominent pattern where larger species display proportionally elongate facial skeletons and smaller braincases. It was recently proposed that CREA arises from biomechanical effects of cranial scaling when diets are similar. Thus, deviations from CREA should occur with changes in cranial biomechanics, for example due to dietary change. Here, we test this using 3D geometric morphometric analysis in a dataset of Australian murine crania, which are highly allometric. We contrast allometric and non-allometric variation in the cranium by comparing evolutionary mode, allometry, ordinations, as well as allometry, integration, and modularity in functional modules. We found evidence of stabilising selection in allometry-containing and size-free shape, and substantial non-allometric variation aligned with dietary specialisation in parallel with CREA. Integration among cranial modules was higher, and modularity lower, with size included, but integration between rostrum and cranial vault, which are involved in the CREA pattern, dropped dramatically after size removal. Our results thus support the hypothesis that CREA is a composite arising from selection on cranial function, with substantial non-allometric shape variation occurring alongside CREA where dietary specialisation impacts selection on gnawing function. This emphasises the need to research mammalian cranial evolution in the context of allometric and non-allometric selection on biomechanical function.

Hemifacial microsomia: a scoping review on progressive facial asymmetry due to mandibular deformity.

PURPOSE: This scoping review explores various parameters of the mandible in progressive facial asymmetry (FA) in hemifacial microsomia (HFM) patients, highlighting its relationship with sex, population, and age group. METHODS: The review was based on a comprehensive search of PubMed, EBSCOhost, and Web of Science. Eligible studies that met the inclusion criteria form part of the selection study. The included studies were appraised using screening and quantitative criteria of mixed-method appraisal tools. The authors utilised a pre-set data extraction form to obtain information from the included studies. RESULTS: Eleven studies met the inclusion criteria. The mandible parameters used were angular measurements, chin point, ramal height, body length, and total length. There was no relationship between FA and sex in HFM patients in the included studies. Most of the studies were comprised of European participants (55%), followed by Americans (36%) and Chinese (9%). The age groups included in the selected studies were categorised as dentition age (18%), early-to-middle childhood (18%), and varied ages (64%). The data presented in this review only pertains to the anomalous characteristics recorded on the affected side in HFM patients. No concomitant control data was recorded in this review. CONCLUSION: An assessment of the included studies revealed that FA does not increase with age in HFM. Hence, FA is non-progressive in HFM patients. This information is relevant to diagnosing and managing HFM patients. More reports are needed on the progression of FA in HFM patients.

Face-brain correlates as potential sex-specific biomarkers for schizophrenia and bipolar disorder.

Given the shared ectodermal origin and integrated development of the face and the brain, facial biomarkers emerge as potential candidates to assess vulnerability for disorders in which neurodevelopment is compromised, such as schizophrenia (SZ) and bipolar disorder (BD). The sample comprised 188 individuals (67 SZ patients, 46 BD patients and 75 healthy controls (HC)). Using a landmark-based approach on 3D facial reconstructions, we quantified global and local facial shape differences between SZ/BD patients and HC using geometric morphometrics. We also assessed correlations between facial and brain cortical measures. All analyses were performed separately by sex. Diagnosis explained 4.1 % - 5.9 % of global facial shape variance in males and females with SZ, and 4.5 % - 4.1 % in BD. Regarding local facial shape, we detected 43.2 % of significantly different distances in males and 47.4 % in females with SZ as compared to HC, whereas in BD the percentages decreased to 35.8 % and 26.8 %, respectively. We detected that brain area and volume significantly explained 2.2 % and 2 % of facial shape variance in the male SZ - HC sample. Our results support facial shape as a neurodevelopmental marker for SZ and BD and reveal sex-specific pathophysiological mechanisms modulating the interplay between the brain and the face.

Morphological and Molecular Analysis of Two Mycophagous Nematodes, Aphelenchoides bicaudatus and A. rutgersi (Nematoda: Aphelenchoididae) from Florida Strawberry.

From 2016 to 2021, nematode surveys in Florida strawberry fields revealed several species of foliar nematodes (Aphelenchoides spp.). Aphelenchoides besseyi sensu stricto was detected only in 2016 and 2017 on photosynthetic strawberry leaves/buds, but other not well characterized populations of Aphelenchoides sp. were found on declining/dessicated leaves. Morphological analyses showed that these samples of Aphelenchoides sp. consisted of A. bicaudatus, a species detected in Florida for the first time, and A. rutgersi, a species previously reported in Florida from the citrus rhizosphere. These two species differed from A. besseyi in the shape of their tail terminus: bifurcate in A. bicaudatus; mucronate with a ventral thin mucro in A. rutgersi; and stellate in A. besseyi. One population each of these species was used for morphological and molecular analyses after being reared on Monilinia fructicola. Body and tail length differences were observed among Florida A. bicaudatus and other populations from the Far East and South Africa. Phylogenetic analyses of the rRNA gene sequences showed that Florida A. bicaudatus grouped with those of species from South Korea, Taiwan, and the Netherlands and several other populations listed as Aphelenchoides sp. from Brazil, Costa Rica, and Japan, which were considered as representatives of A. bicaudatus in this study. Similarly, sequences of Florida A. rutgersi grouped with those from environmental samples in Japan and North Carolina, which were listed as Aphelenchoides sp. and were considered as representatives of A. rutgersi in this study. Photosynthetic strawberry leaf samples were free from both A. bicaudatus and A. rutgersi, indicating that these two species did not damage strawberry. They were associated with desiccated leaves and/or propagative stolons, usually infected by fungi, confirming that they are mycetophagous under field conditions in this study. Results of soybean leaf inoculation on moist filter paper containing A. bicaudatus specimens showed that this species could become phytophagous under artificial conditions. Nematodes penetrated the leaf epidermis and migrated into the mesophyll causing leaf tissue discoloration/necrosis, which remained localized within the infested area. Soybean leaf damage was almost negligible, and no nematode reproduction was observed in the inoculated soybean areas.

Craniofacial morphological variability in orthodontic patients with non-syndromic orofacial clefts: an approach using geometric morphometrics.

OBJECTIVES: Orofacial clefts are complex congenital anomalies that call for comprehensive treatment based on a thorough assessment of the anatomy. This study aims to examine the effect of cleft type on craniofacial morphology using geometric morphometrics. MATERIALS AND METHODS: We evaluated lateral cephalograms of 75 patients with bilateral cleft lip and palate, 63 patients with unilateral cleft lip and palate, and 76 patients with isolated cleft palate. Generalized Procrustes analysis was performed on 16 hard tissue landmark coordinates. Shape variability was studied with principal component analysis. In a risk model approach, the first nine principal components (PC) were used to examine the effect of cleft type. RESULTS: We found statistically significant differences in the mean shape between cleft types. The difference is greatest between bilateral cleft lip and palate and isolated cleft palate (distance of means 0.026, P = 0.0011). Differences between cleft types are most pronounced for PC4 and PC5 (P = 0.0001), which together account for 10% of the total shape variation. PC4 and PC5 show shape differences in the ratio of the upper to the lower face, the posterior mandibular height, and the mandibular angle. CONCLUSIONS: Cleft type has a statistically significant but weak effect on craniofacial morphological variability in patients with non-syndromic orofacial clefts, mainly in the vertical dimension. CLINICAL RELEVANCE: Understanding the effects of clefts on craniofacial morphology is essential to providing patients with treatment tailored to their specific needs. This study contributes to the literature particularly due to our risk model approach in lieu of a prediction model.

Changes in the wing shape and size in fruit flies exposed to micro and nanoplastics.

Geometric morphometrics analysis (GMA) is a well-known technique to identify minute changes in Drosophila wings. This study aimed to determine potential changes in Drosophila wings shape and size after exposure to polystyrene nanoplastics (NPs) (50 nm) and microplastics (MPs) (1 µm). Flies were exposed from eggs to pupal eclosion and analyzed using GMA. Results revealed a difference in shape and size between male and female wings, as expected, due to sexual dimorphism. Therefore, wings were analyzed by sex. Wings of MPs and NPs treated females were elongated compared to controls and had a constriction of the wing joint. Additionally, MPs treated female flies had the most dissimilar shape compared to controls. In male flies, NPs flies had smaller wings compared to MPs and control flies. Compared to control, NPs wings of males were shrunken at the joint and in the entire proximal region of the wing. However, male MPs wings had a narrower anal region and were slightly elongated. These results reveal that wing shape and size can change in a different way based on the sex of the flies and size of plastic particles that larvae interacted with. All the changes in the wings occurred only within the normally allowed wing variation and treatment with NPs/MPs did not cause development of the aberrant phenotypes. Results can pave the way for further understanding of how MPs and NPs can alter phenotypes of flies.

MRI-based axis-referenced morphometric model corresponding to lamellar organization for assessing hippocampal atrophy in dementia.

Research on the local hippocampal atrophy for early detection of dementia has gained considerable attention. However, accurately quantifying subtle atrophy remains challenging in existing morphological methods due to the lack of consistent biological correspondence with the complex curving regions like the hippocampal head. Thereby, this article presents an innovative axis-referenced morphometric model (ARMM) that follows the anatomical lamellar organization of the hippocampus, which capture its precise and consistent longitudinal curving trajectory. Specifically, we establish an "axis-referenced coordinate system" based on a 7 T ex vivo hippocampal atlas following its entire curving longitudinal axis and orthogonal distributed lamellae. We then align individual hippocampi by deforming this template coordinate system to target spaces using boundary-guided diffeomorphic transformation, while ensuring that the lamellar vectors adhere to the constraint of medial-axis geometry. Finally, we measure local thickness and curvatures based on the coordinate system and boundary surface reconstructed from vector tips. The morphometric accuracy is evaluated by comparing reconstructed surfaces with those directly extracted from 7 T and 3 T MRI hippocampi. The results demonstrate that ARMM achieves the best performance, particularly in the curving head, surpassing the state-of-the-art morphological models. Additionally, morphological measurements from ARMM exhibit higher discriminatory power in distinguishing early Alzheimer's disease from mild cognitive impairment compared to volume-based measurements. Overall, the ARMM offers a precise morphometric assessment of hippocampal morphology on MR images, and sheds light on discovering potential image markers for neurodegeneration associated with hippocampal impairment.

Morphometrics and Phylogenomics of Coca (Erythroxylum spp.) Illuminate Its Reticulate Evolution, With Implications for Taxonomy.

South American coca (Erythroxylum coca and E. novogranatense) has been a keystone crop for many Andean and Amazonian communities for at least 8,000 years. However, over the last half-century, global demand for its alkaloid cocaine has driven intensive agriculture of this plant and placed it in the center of armed conflict and deforestation. To monitor the changing landscape of coca plantations, the United Nations Office on Drugs and Crime collects annual data on their areas of cultivation. However, attempts to delineate areas in which different varieties are grown have failed due to limitations around identification. In the absence of flowers, identification relies on leaf morphology, yet the extent to which this is reflected in taxonomy is uncertain. Here, we analyze the consistency of the current naming system of coca and its four closest wild relatives (the "coca clade"), using morphometrics, phylogenomics, molecular clocks, and population genomics. We include name-bearing type specimens of coca's closest wild relatives E. gracilipes and E. cataractarum. Morphometrics of 342 digitized herbarium specimens show that leaf shape and size fail to reliably discriminate between species and varieties. However, the statistical analyses illuminate that rounder and more obovate leaves of certain varieties could be associated with the subtle domestication syndrome of coca. Our phylogenomic data indicate extensive gene flow involving E. gracilipes which, combined with morphometrics, supports E. gracilipes being retained as a single species. Establishing a robust evolutionary-taxonomic framework for the coca clade will facilitate the development of cost-effective genotyping methods to support reliable identification.

From slenderness to robustness: Understanding long bone shape in sigmodontine rodents.

The morphological evolution of the appendicular skeleton may reflect the selective pressures specific to different environments, phylogenetic inheritance, or allometry. Covariation in bone shapes enhances morphological integration in response to ecological specializations. In contrast to previous multivariate studies using classical linear morphometry, we use a geometric morphometric approach to explore the morphological diversity of long bones and examine relationships between ecological categories and morphological characters in a species-rich and ecomorphologically diverse group of rodents. We examined the humerus, ulna, femur, and tibiofibula of 19 sigmodontine species with different locomotor types (ambulatory, quadrupedal-saltatorial, natatorial, semifossorial and scansorial) to investigate the influence of locomotor type and phylogeny on limb bone shape and morphological integration of the appendicular skeleton. This study represents the most detailed examination of the morphological diversity of long bones in sigmodontines, employing geometric morphometrics within an ecomorphological framework. Our results indicate that functional demands and evolutionary history jointly influence the shape of forelimb and hindlimb bones. The main variation in bone shape is associated with a slenderness-robustness gradient observed across all ecological categories. Quadrupedal-saltatorial species, with their need for agility, possess slender and elongated limbs, while natatorial and semifossorial species exhibit shorter and more robust bone shapes, suited for their respective environments. This gradient also influences bone covariation within limbs, demonstrating interconnectedness between elements. We found functional covariation between the ulna-tibiofibula and humerus-tibiofibula, likely important for propulsion, and anatomical covariation between the humerus-ulna and femur-tibiofibula, potentially reflecting overall limb structure. This study demonstrates that the versatile morphology of long bones in sigmodontines plays a critical role in their remarkable ecological and phylogenetic diversification.

Anatomy and mobility in the adult cadaveric craniocervical junction.

Genetic diseases with craniofacial malformations can be associated with anomalies of the craniocervical joint (CCJ). The functions of the CCJ are thus impaired, as mobility may be either limited by abnormal bone fusion causing headaches, or exaggerated in the case of hypermobility, which may cause irreparable damage to the spinal cord. Restoring the balance between mobility and stability requires surgical correction in children. The anatomy and biomechanics of the CCJ are quite unique, yet have been overlooked in the past decades. Pediatric evidence is so scarce, that investigating the adult CCJ is our best shot to disentangle the form-function relationships of this anatomical region. The motivation of the present study was to understand the morphological and functional basis of motion in the CCJ, in the hope to find morphological features accessible from medical imaging able to predict mobility. To do so, we have quantified the in-vitro kinematics of the CCJ in nine cadaveric asymptomatic adults, and estimated a wide range of mobility variables covering the complexity of spinal motion. We compared these variables with the shape of the occipital, the atlas and the axis, obtained using a dense geometric morphometric approach. Morphological joint congruence was also quantified. Our results suggest a strong relationship between bone shape and motion, with the overall geometry predicting best the primary movements, and the joint facets predicting best the secondary movements. We propose a functional hypothesis stating that the musculoligamental system determines movements of great amplitude, while the shape and congruence of joint facets determine the secondary and coupled movements, especially by varying the geometry of bone stops and the way ligaments are tensioned. We believe this work will provide valuable insights in understanding the biomechanics of the CCJ. Furthermore, it should help surgeons treating CCJ anomalies by enabling them to translate objectives of functional and clinical outcome into clear objectives of morphological outcome.

Discovery and Characterization of Four Aphelenchid Species from Cultivated Regions of Southern Alberta, Canada.

The nematode family Aphelenchoididiae is considered fungal-feeding, predatory, or root hair feeders. Some members of this family are universally present in agricultural landscapes and are an integral part of soil health and conservation studies. In the present soil nematode biodiversity survey, we detected four species of the genera Aphelenchus, Aphelenchoides, and Robustodorus. Because fungal-feeding nematodes from southern Alberta have not previously been reported, we conducted a detailed morphological and molecular investigation, identifying these species as Aphelenchus avenae, Aphelenchoides limberi, Aphelenchoides prairiensis n. sp. and Robustodorus paramegadorus n. sp. The first two species we document as new records from southern Alberta, whereas A. prairiensis n. sp. and R. paramegadorus n. sp. we describe in detail as new taxa. Briefly, A. prairiensis n. sp. is an amphimictic species having 4 lateral lines; hemispherical anteriorly flattened lip region; delicate stylet and swelling-like stylet knobs; excretory pore at the posterior edge of nerve ring. Female tail conical, gradually tapering towards a truncated end with single mucro. Spicule 23.0 (20.0-25.0) µm long having elongated rounded condylus, small, blunt conical rostrum, and lamina that gradually tapers towards the rounded distal end; three pairs of caudal papillae were present on the male tail. Robustodorus paramegadorus n. sp., is a parthenogenetic species with 3 lines in the lateral fields; lip region rounded, anteriorly flattened; stylet robust, with knobs rounded to bean-shaped; excretory pore located posterior to nerve ring; reproductive components were quite indiscernible with a short 24.0 (18.0-27.0) µm post-vulval uterine sac; tail conical, ending with pointed to wedge-shaped tip. We performed molecular characterizations for each species and constructed phylogenetic trees to study the phylogenetic relationship of these aphelenchid species. The discovery of A. prairiensis n. sp. and R. paramegadorus n. sp. indicates that soil nematode diversity is relatively unexplored in southern Alberta. The findings of this study will significantly enhance the identification processes and may contribute towards future soil health and biodiversity efforts.

Description of a Remarkable New Skate Species of Leucoraja Malm, 1877 (Rajiformes, Rajidae) from the Southwestern Indian Ocean: Introducing 3D Modeling as an Innovative Tool for the Visualization of Clasper Characters.

A remarkable new deep-water skate, Leucoraja longirostris n. sp., is described based on eight specimens caught during different expeditions to the southern Madagascar Ridge in the southwestern Indian Ocean. The new species differs from all congeners by its remarkably long and acutely angled snout (horizontal preorbital length 17.2-22.6% TL vs. 8.5-11.9% TL and 4.2-6.1 vs. 1.7-3.5 times orbit length, snout angle 65-85° vs. 90-150°). Furthermore, it is apparently endemic to the Madagascar Ridge, distant from the known distribution areas of all congeners. In addition to L. fullonica and L. pristispina, L. longirostris n. sp. is also the only species with plain dorsal coloration. Furthermore, the new species is the only Leucoraja species with an external clasper component dike and, besides L. wallacei, the only one with four dorsal terminal (dt) cartilages. The shape of the accessory terminal 1 (at1) cartilage with four tips is also unique within the genus. A new approach for the visualization of the clasper characters is introduced based on 3D models of all skeletal and external features. This enables a much easier and much more precise interpretation of every single clasper component, of the entire structure, and, in particular, the relationship between external features and skeletal cartilages. A new English translation of the first diagnosis of Leucoraja is provided, along with a revised generic diagnosis and a key to the species of Leucoraja in the Indian Ocean.

Using linear measurements to diagnose the ecological habitat of Spinosaurus.

Much of the ecological discourse surrounding the polarising theropod Spinosaurus has centred on qualitative discussions. Using a quantitative multivariate data analytical approach on size-adjusted linear measurements of the skull, we examine patterns in skull shape across a range of sauropsid clades and three ecological realms (terrestrial, semi-aquatic, and aquatic). We utilise cluster analyses to identify emergent properties of the data which associate properties of skull shape with ecological realm occupancy. Results revealed terrestrial ecologies to be significantly distinct from both semi- and fully aquatic ecologies, the latter two were not significantly different. Spinosaurids (including Spinosaurus) plotted away from theropods in morphospace and close to both marine taxa and wading birds. The position of nares and the degree of rostral elongation had the greatest effect on categorisation. Comparisons of supervised (k-means) and unsupervised clustering demonstrated categorising taxa into three groups (ecological realms) was inappropriate and suggested instead that cluster division is based on morphological adaptations to feeding on aquatic versus terrestrial food items. The relative position of the nares in longirostrine taxa is associated with which skull bones are elongated. Rostral elongation is observed by either elongating the maxilla and the premaxilla or by elongating the maxilla only. This results in the nares positioned towards the orbits or towards the anterior end of the rostrum respectively, with implications on available feeding methods. Spinosaurids, especially Spinosaurus, show elongation in the maxilla-premaxilla complex, achieving similar functional outcomes to elongation of the premaxilla seen in birds, particularly large-bodied piscivorous taxa. Such a skull construction would bolster "stand-and-wait" predation of aquatic prey to a greater extent than serving other proposed feeding methods.

Differentiation of Synanthropic Fleas from Andalusia (Spain) through Geometric Morphometrics Analysis.

Fleas (Siphonaptera) are ectoparasitic hematophagous insects responsible for causing bites and itchy skin conditions in both humans and animals. Furthermore, they can act as vectors of different pathogens of a wide variety of diseases worldwide, including bartonellosis, rickettsiosis, and bubonic plague. Accurate identification of fleas is necessary for the study of their epidemiology, prevention, and control. In addition to traditional morphological classification approaches and molecular biology techniques, geometric morphometrics is increasingly proving to be a useful complementary tool for discriminating between Siphonaptera taxa. With the objective of determining the capacity of this technique to identify and differentiate synanthropic fleas, a principal component analysis was carried out on populations of Ctenocephalides felis, Pulex irritans, and Archaeopsylla erinacei collected in distinct regions of Andalusia (Spain). The analysis carried out on 81 male and female specimens revealed factorial maps that allowed the differentiation of the populations under study, with only partial overlaps that did not prevent their correct identification. Global size differences were also detected, with a slightly larger size in P. irritans males and a bigger size in A. erinacei females. Therefore, the present study emphasizes the role of geometric morphometrics as a useful complementary technique in taxonomic studies of arthropods, especially in the case of flea specimens lacking representative morphological features.

Revisions of the clavipes and pruni species groups of the genus Merodon Meigen, 1803 (Diptera, Syrphidae).

This study focuses on the avidus-nigritarsis lineage within the genus Merodon, exploring morphological, genetic, and distributional aspects of two related assemblies within this lineage: the clavipes and pruni species groups. An integrative taxonomic approach was followed to ensure comprehensive species identification and validation, using adult morphology, wing geometric morphometrics, and genetic analysis of the mtDNA COI gene. In the clavipes group, seven species were identified, including three new species: M.aenigmaticus Vujic, Radenkovic & Likov, sp. nov., M.latens Vujic, Radenkovic & Likov, sp. nov., and M.rufofemoris Vujic, Radenkovic & Likov, sp. nov. In the pruni group, our revision revealed a new species, M.aequalis Vujic, Radenkovic & Likov, sp. nov., and the revalidation of Merodonobscurus Gil Collado, 1929, stat. rev. Merodonpallidus Macquart, 1842 is redescribed. Diagnoses, identification keys to species, and distribution maps are provided, and neotypes for Syrphusclavipes Fabricius, 1781 and Merodonquadrinotatus (Sack, 1931) are designated. Additionally, the following new synonyms are proposed: M.clavipesalbus syn. nov., M.clavipesater syn. nov., M.clavipesniger syn. nov., and M.splendens syn. nov. are junior synonyms of M.clavipes; and M.veloxarmeniacus syn. nov. and M.veloxanathema syn. nov. are junior synonyms of M.velox.