Belgium

Understanding the feeding behaviour and diet of early tetrapods, such as temnospondyl amphibians,is essential to understand their ecological roles, particularly during their transition from aquatic toterrestrial environments. A DFG-funded project, as part of a research unit focused on the life historystrategies of early tetrapods, aims to illuminate temnospondyl feeding strategies and dietary habitsby integrating ontogenetic, phylogenetic, and functional analyses. The research is organised into fivecomprehensive work packages. Firstly, the ontogenetic differences in various temnospondyl feedingapparatuses are examined using advanced µCT scanning, digital dissection, retrodeformation, anddigital repairs to reconstruct key structures crucial for understanding their feeding mechanics.Secondly, distinct morphotypes reflecting the evolutionary and developmental biology oftemnospondyl feeding are identified using data compiled from the first work package. Thirdly, byapplying digital modelling techniques, we reconstruct probable aquatic feeding strategies associatedwith the identified morphotypes, providing insights into how these organisms might have fed in theiraquatic habitats. In the fourth work package, terrestrial feeding strategies are delineated bycorrelating morphotype data with contemporary studies on vertebrate feeding patterns, enablinghypotheses about their terrestrial adaptations. Finally, we synthesise fossil evidence with ourmorphotype analyses to reconstruct dietary specialisations, enhancing our understanding of thepaleoecology of temnospondyls. This multidisciplinary approach allows for a comprehensiveunderstanding of how temnospondyls adapted their feeding mechanisms across environments andontogeny, offering new perspectives on their life histories during pivotal evolutionary transitions.

SEB Conference 2025

The Feeding Dead: simulating early tetrapod feeding

water-to-land

temnospondyl

evolution

feeding

modelling

poster

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The coexistence of numerous sympatric predatory marine reptiles in the Western Interior Seaway (WIS), a vast inland sea that stretched across North America during the Late Cretaceous, suggests ecological partitioning within higher trophic niches. Many studies have focused on dental morphology as a proxy to infer feeding habits of aquatic tetrapods, but much more ecological insight may be gained through simulations of mechanical performances. Here, we conducted the first, large-scale, comparative study of WIS marine reptile jaw biomechanics, applying muscle-driven finite element analyses (FEA) on a dataset of high-resolution three-dimensional models of Santonian-Maastrichtian mosasaurids and polycotylid plesiosaurians. For comparative purposes, mosasaur jaws were modeled with a fused symphysis and immobile intramandibular joint, forming a single functional element. Muscle insertions were identified to reconstruct jaw adductor muscles and assess respective muscle and bite force. We used Metafor software to simulate realistic muscle traction dynamics during biting, including simulations at multiple opening angles and multiple biting locations. We recover clearly distinct biomechanical performances among the sample, notably between the slender-snouted mosasaurids (e.g., Clidastes) and polycotylids, and the robust-jawed mosasaurids (e.g., Prognathodon). By integrating jaw size, mechanical efficiency, and strain, we provide strong support for niche partitioning among these marine predators, as influenced by physical biting capabilities. Our results offer deeper insight into feeding ecologies in Late Cretaceous marine predators, and provide a unified protocol to assess niche partitioning in sympatric marine reptiles from well-sampled regions.

Niche partitioning and feeding performance in Late Cretaceous marine reptiles from the Western Interior Seaway

The equid locomotor transition is one of the most iconic morphofunctional shifts in terrestrial mammals. Throughout their evolution, equids reduced their side-digits, with different phylogenetic clades exhibiting greater or lesser degrees of digit reduction. Over 80% of equid genera retained side-digits, despite many species coexisting with monodactyl equids for over 7 Ma. In this continuing study, we shed light on the functionality of the side-digits of extinct equids using an extant morphological bracket, comparing toe-ground interception across ecologically diverse ungulates with side-digits. Using high-resolution 3D surface scans, joint range-of-motion was estimated from osteological material of modern and extinct ungulate forelimbs. Distal limb rigs were built and analysed, rotating the third proximal phalange parasagittally at biologically realistic, regularly spaced intervals. Toe-to-ground interception for the side-digits was scored for the varying degrees of central digit extension (simulating high-performance actions), and under increasingly compliant substrates (mimicking different underfoot conditions). Our results demonstrate widespread functionality in the side digits of tridactyl equids, with significant differences found between earlier browsing forms (e.g. Anchitherium) and later grazing forms (e.g. Hipparion). High-performance actions, such as galloping or jumping/landing would have caused the side digits of almost all tridactyl equids to impact the substrate. Our work confidently refutes the notion of functional redundancy in equid side-digits. The extant morphological framework within which this study was conducted also provides a suite of potential extant analogues for verifying simulations of extinct equid locomotion, and thus paves the way for more integrative investigations involving in-vivo and in-silico locomotor kinematics.

Still using modern ungulate analogues to explore equid side-toe function through an iconic evolutionary transition...

Single-toed (monodactyl) equids (horses, zebras, asses) are the only surviving members of the family Equidae, despite living contemporaneously with three-toed (tridactyl) forms for c.15 Ma. Among the tridactyl forms, a trend of side-digit reduction is observed, raising the question about the energetic advantage of digit loss. The inertial load hypothesis describes the reduction (and eventual loss) of side-digits in equids as a means to minimize energetic cost during locomotion, linked to reducing inertial load (or moment of inertia, MOI) of the limbs by minimizing their distal mass. In this study, we tested this hypothesis by estimating and comparing inertial loads of tridactyl equid limbs, both with and without side-digits. Additionally, we compared the results of the tridactyl and monodactyl equids, while accounting for differences in limb size, to investigate the effect of side-digit loss across equid evolution. MOI was calculated on soft tissue limb reconstructions created using 3D models of (fossil) bones. A validation analysis using 3D renders of cadaver specimens verified the predictability of these reconstructions. We demonstrate that the entire limb MOI with regard to the scapular rotation centre is significantly smaller without side-digits. However, the difference is very small, and its functional significance can be questioned.  Size-corrected MOI between monodactyl and tridactyl taxa suggest overall significant differences (monodactyl equids with lower MOI); however, distal limb mass comparisons (e.g. pastern segments) showed no signs of the effect of side-digits. Our results hint at limb segment allometry as a more notable influence on MOI reduction during horse evolution.

Investigating the biomechanical efficiency of horse limbs through their iconic distal limb evolution.

Cranial shape in extinct fossilised species provides a vital puzzle piece to our understanding of their feeding behaviour which cannot be observed in real time. The carnivorous theropod MOR693 Allosaurus jimmadseni fossil offers insight into its feeding function and the palaeo-ecology of the Late Jurassic geological period. A. jimmadseni possesses a distinctive cranial anatomy, displaying large fenestrae and a thin cranio-caudally elongated skull. The skull’s lightweight anatomy has led researchers to hypothesise a “puncture and pull” feeding behaviour, in which an animal captures prey with a puncture bite, and proceeds to tear with a pulling motion. Using 3D scans of the MOR693 skull and applying a finite element analysis, I obtained the maximum, average, and minimum total von Mises stress in the skull during different biting angles. My results report that the 0-30° bites (puncture) exhibited the highest stress values, while the 90° bite (pull) showed the lowest. A consistent decrease from a 0° to a 90° bite in the maximum, average, and minimum stress indicates that the skull experienced the least amount of stress during the pulling aspect of feeding. Low-stress values suggest an evolutionarily advantageous feeding motion in this dinosaur, therefore it is reasonable to conclude that the A. jimmadseni utilised this feeding strategy. The results of this research present that the skull was likely adapted for a pulling dominant feeding behaviour rather than a puncture, further supporting the puncture and pull feeding hypothesis in the A. jimmadseni.

Using the Allosaurus jimmadseni Skull Structure as a Puzzle Piece to Feeding Function

In extinct and extant species, some insights on joint function can be gained using bone morphology. Models of joints tend to use tendons to control joint function, often giving little or no insight on the role of ligaments in controlling the range of motion of a joint. This study presents an algorithm to automatically compute ligament attachment sites for a flexion-extension joint using optimisation, given bone morphology and required range of motion. To start with, the focus is on the collateral ligaments of the human finger Distal Inter-Phalangeal (DIP) joint.
The algorithm takes bone profiles and the required maximum flexion and extension angles as inputs. First, a grid of possible attachment sites is generated from the bone profiles. Using this grid, a discrete stage determines the best combination of attachment sites by minimising an objective function subject to a set of geometric constraints. This seeds the second stage– a continuous domain local optimisation which refines the attachment coordinates by minimising the error between required and computed range of motion. The algorithm’s outputs are attachment site coordinates of the two edges of a band of collateral ligaments capable of achieving the required range of motion. The outputs were verified by adding ligaments computed by the algorithm to an OpenSim simulation model and confirming that the required range of motion was achieved.
In contrast to other published research, the algorithm presented here computes ligament attachment sites based on range of motion - deriving form from function rather than relating form to function.

From Function to Form : Computing Collateral Ligament Attachments

Trap-jaw ants are recognized for their generally elongated mandibles that snap at remarkable speeds, having evolved among nine genera and three subfamilies. Despite superficial similarities, mandible morphology varies considerably, potentially affecting bite performance. To investigate these effects, we measured functional traits — mechanical advantage, cuticle thickness, and second moment of area (I) — and conducted finite element analysis (FEA) simulating a strike bite on 3D mandible reconstructions of 25 species from eight genera and two subfamilies of trap-jaw ants. We performed Principal Component Analysis with the functional traits and FEA-derived stress values and hypothesized that species distribution in this multivariate space would reflect their phylogenetic relationships. Species mostly grouped with their generic relatives, except Anochetus and Orecthognathus, which showed broader distributions. The distribution of trap-jaw genera also resembled their phylogenetic relatedness, but Myrmicinae and Ponerinae subfamilies did not form distinct clusters, as was initially anticipated. FEA stress data were relevant for grouping species with more elongated mandibles, such as Acantognathus spp. and Strumigenys denticulata. Odontomachus spp. and Daceton armigerum clustered due to their higher values ofI normalised by cross-section shape. Strumigenys spp. with shorter mandibles grouped due to their high mechanical advantage, I corrected by mandible length, cuticle thickness, and the low-stress values they exhibited under bite loading. Although our results only partially support the hypothesis that mandible function aligns with the phylogenetic relationships of trap-jaw ants, they highlight the functional consequences of mandible morphological variation in the context of the outstanding strike impacts these ants are submitted to.

Morphology drives functional performance variation: the case of trap-jaw ant mandibles

The arboreal environment is a complex three-dimensional environment that presents functional challenges. Despite these challenges, many clades of tetrapods have colonised this environment independently. So far, only a handful of studies investigate the impact of living in trees on the morphology in a large macroevolutionary sample. Here, we investigate whether there is an effect of degree of arboreality on radius shape. To do so, we compared radius shape across arboreal and terrestrial species of carnivorans and primates. Radius shape is an interesting structure as it influences forearm movement and hand position, which are vital in arboreal environments. Our sample comprises 239 specimens belonging to 160 species and, is representative of the locomotor diversity of carnivorans and primates. We used 3D geometric morphometrics to quantify the shape of the radius. Comparative phylogenetic methods were applied to understand the influence of size, locomotion and evolutionary history of each clade on radial shape. Our results showed a significant impact of the locomotion and morphological similarities in the radial shape among species with similar arboreal locomotion. Furthermore, the morphological diversity of radial shapes in carnivorans and primates is low, in contrast to the high diversity observed in terrestrial species. This suggests that arboreal environments impose greater constraints on the radial morphology in carnivorans and primates, which is consistent with results obtained in other vertebrates.

Arboreal adaptations constrain the morphological evolution of the radius bone in primates and carnivorans.

Grain yield is a key determinant of cereal crop productivity, with spike morphology playing a crucial role in its assessment. Traditional spike characterization methods are often labor-intensive and time-consuming, limiting their scalability for large-scale breeding programs. To address this challenge, we present an advanced image-based tool leveraging deep learning methodologies for non-invasive, high-throughput spike phenotyping. The system utilizes a U-Net model trained on 200 annotated spike images, incorporating data augmentation techniques such as rotation and scaling to enhance robustness. With the Dice coefficient as the loss function and the Adam optimizer, the model was trained for 60 epochs with early stopping to prevent overfitting. Additionally, adaptive thresholding and the Segment Anything Model (SAM) were evaluated, achieving Dice coefficients of 0.95 and 0.98, respectively, demonstrating the effectiveness of automated spike segmentation. The post processing of segmented grains extracts key morphological traits, including spike length, grain number, grain width, grain length, and grain area, facilitating precise yield analysis. This innovation enhances the efficiency of crop breeding research by providing an accurate, non-destructive, and scalable solution for spike trait analysis.

Automated X-ray-Based Spike Analysis for Grain Characterization

The maize plastochron1 (pla1) mutant exhibits a shortened plastochron (accelerated leaf initiation) and reduced plant growth. This remarkable phenotype suggests a role for PLA1 in regulating leaf initiation and growth in the maize shoot apical meristem (SAM). The SAM is a highly complex structure where stem cells gradually differentiate into plant organs in a spatially coordinated manner. However, the transcriptional mechanisms by which PLA1 influences these developmental processes remain unclear. To investigate how PLA1 affects plant architecture at the molecular level, we applied spatial transcriptomics to visualize the expression of 500 genes in wild-type and pla1 mutant shoot apices. Our analysis showed that PLA1 is expressed at the boundary between undifferentiated and differentiated cells, suggesting a role in regulating cell division and organ initiation. Developmental trajectory analysis tracing transcriptional changes from stem cells to differentiated cells revealed overlaps of PLA1 with stem cell markers such as Knotted1 and differentiation markers such as YABBY14, further supporting its regulatory function. Comparisons between wild-type and pla1 mutants revealed significant transcriptional changes, particularly in auxin metabolism, indicating an important role for PLA1 in (hormonal) regulation of the SAM. These findings provide novel insights into the transcriptional regulation of the maize meristem SAM and plastochron regulation, showcasing spatial transcriptomics and its downstream data-analysis as a valuable tool for studying plant development.

Plastochron regulation in maize: spatial transcriptomics reveals transcriptional changes in the plastochron1 mutant.

Overall plant architecture (consisting of the number, spacing and angle of secondary root and shoot branches) determines the efficiency of crops to capture essential resources such as water and nutrients below-ground, and light above-ground. Plant architecture is critically regulated by gravitropic growth, and recently, members of the highly conserved LAZYgene family have been demonstrated to play crucial roles in regulation of branching angle, a key determinant of plant architecture. Our previous work identified a novel dominant point mutation in LAZY4, (described as lazy4D) through an EMS mutagenesis screen in the model plant, Arabidopsis. Lateral roots in the lazy4Dmutant demonstrate steeper rooting, a highly desirable trait, that maximises nitrogen uptake, drought tolerance and carbon sequestration in cereal crops, making LAZY4 (and related LAZY genes) attractive targets for gene-editing to engineer deeper rooting in crop plants. However, the mechanistic basis for LAZY4dependent-regulation of root angle remains uncharacterised. Using live cell bioimaging and molecular genetic techniques, we determined that lazy4Dinfluences root growth angle in a dose-dependent manner, and further, that root LAZYs interact with D6PK proteins to regulate PIN polarisation and/or activity to regulate  lateral root growth angle.  Further we show that an MKK-MPK31,2  phosphorylation module is required forLAZY4, but notlazy4d dependent regulation of growth angle. Collectively, our work sheds novel insights into the molecular mechanisms that underpin thelazy4D (and more broadly,LAZY) dependent regulation of root and shoot branching angle in flowering plants.

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