Laura A. B. Wilson’s research while affiliated with Australian National University and other places

Generative models are an underutilized tool in bioarchaeology that make it possible to directly interrogate how age-at-death is influenced by varied risk of exposure to stressors, while accounting for factors which are ordinarily invisible to bioarchaeologists. Further, the visibility of suspected differences within populations at the sorts of sample sizes common to bioarchaeology can also be examined, helping to inform interpretation of findings. In the present study, cohorts of 50, 100, 500, and 1000 individuals aged 0 years were generated. Each individual was assigned a frailty value, and to either high or low risk groups. These cohorts were run through simulation models in which exposure to stressors varied according to risk group and the severity of stressors if exposed. The difference in mean age-at-death between high and low risk group for each run was tested for significance using Welch's t-test. The model results are used to identify potential minimum sample sizes for bioarcheological research at which true differences in age-at-death due to difference in stressor exposure are likely to be visible. Small cohorts (50 individuals) had low likelihood of detecting true risk group differences in age-at-death except when the difference in exposure to stressors or the severity of the stressor was great enough to produce a mean difference in lifespan of >20 years. The probability of observing a true difference in age-at-death between risk groups increased when the difference in stressor exposure and/or the stressor severity increased for all cohorts. Therefore, group-level differences in lifespan may not be identifiable in small archaeological samples except where stress or inequality is high. The low reliability of results from small samples reiterates the needs to carefully examine equifinality in bioarcheological research, as demonstrated through the application of this model to a case study which examined the Late Woodland phase of the Dickson Mounds. This application assessed the three potential hypotheses put forth by Goodman and Armelagos (1988) to establish how likely they may be when sample size is not a limiting factor on visibility of potential difference within populations.

The platypus and four echidna species are the only living egg-laying mammals and the sole extant representatives of Order Monotremata. The platypus and echidnas are very disparate both morphologically and ecologically: The platypus is a specialized semiaquatic burrowing form that forages for freshwater invertebrates, whereas echidnas are fully ter- restrial and adapted for feeding on social insects and earthworms. It has been proposed that echidnas evolved from a semiaquatic, platypus-like ancestor, but fossil evidence for such a profound evolutionary transformation has been lacking, and this hypothesis remains controversial. Here, we present original data about the Early Cretaceous (108 to 103 Ma) Australian mammal Kryoryctes cadburyi, currently only known from a single humerus, that provides key information relating to this question. Phylogenetic analy- sis of a 536-character morphological matrix of mammaliaforms places Kryoryctes as a stem-monotreme. Three-dimensional whole bone comparisons show that the overall shape of the humerus is more similar to that of echidnas than the platypus, but analysis of micro- structure reveals specializations found in semiaquatic mammals, including a particularly thick cortex and a highly reduced medullary cavity, present in the platypus but absent in echidnas. The evidence suggests Kryoryctes was a semiaquatic burrower, indicating that monotremes first evolved an amphibious lifestyle in the Mesozoic, and providing support for the hypothesis that this is ancestral for living monotremes as a whole. The lineage leading to the modern platypus appears to have been characterized by extremely long term (>100 My) niche conservatism, with echidnas representing a much later reversion to a fully terrestrial lifestyle.

Biological differences between males and females are pervasive. Researchers often focus on sex differences in mean or, occasionally, in variation, albeit other measures can be useful for biomedical and biological research. For instance, differences in skewness (asymmetry of a distribution), kurtosis (heaviness of a distribution’s tails), and correlation (relationship between two variables) might be crucial to improve medical diagnosis and to understand natural processes. Yet, there are currently no meta-analytic ways to measure differences in these metrics between two groups while accounting for sampling error. We propose three effect size statistics to fill this gap: Δsk, Δku, and ΔZr, which measure differences in skewness, kurtosis, and correlation, respectively. Besides presenting the rationale for the calculation of these effect size statistics, we illustrate their potential using a large dataset of mice traits. For example, we found that females show, on average, greater skewness and kurtosis than males in both fat mass and heart weight. Although calculating Δsk, Δku, and ΔZr may require large sample sizes of individual data, technological advancements in data collection create increasing opportunities to use these effect size statistics. Importantly, Δsk, Δku, and ΔZr can be used to compare any two groups, allowing a new generation of meta-analyses that explore such differences and potentially leading to new insights in multiple fields of study.

Key innovations play a crucial role in driving biodiversity and facilitating evolutionary success by enabling organisms to adapt to various ecological niches through the diversification of phenotypic traits. These innovations have been observed in different vertebrate clades, such as mammals evolving hypsodonty to graze on contemporary grasses and bats with the evolution of echolocation, alongside wing acquisition. Recent studies have shed light on the overlooked morphological diversity of the larynx in bats, a key organ involved in echolocation capabilities. Tracheal chambers, found on the first rings of the trachea, are enigmatic components of the laryngeal complex whose origins and functions have yet to be fully elucidated. We hypothesised that these structures may show evolutionary convergence and represent a key innovation associated with laryngeal echolocation. The present study examines 50 bat species, their laryngeal cartilages and tracheal chambers. We explored relationships between body mass, sound frequencies, and chamber volumes, as we hypothesise that tracheal chambers may have facilitated laryngeal echolocation capabilities in bats. Ancestral state reconstructions were conducted to understand the evolution of tracheal chambers and laryngeal echolocation behaviours in bats. We conclude that tracheal chambers allow higher frequency sound production and were pivotal for the specialization of high-duty cycle echolocation during the evolution of bats emitting calls nasally, contributing to their ability to thrive in diverse environments. We suggest that tracheal chambers are key innovations that enhance laryngeal echolocation behaviours and the evolutionary success of bats.

The new Editors-in-Chief for the Journal discuss changes to the editorial team, along with their future plans for broadening the Journal’s scope and encouraging submissions across the different article types currently offered by AJZ.

Orofacial morphology in mammals plays a critical role in essential life functions such as feeding and communication, which are influenced by the shapes of these anatomical structures. Bats are known to exhibit highly diversified orofacial morphotypes within their clade, reflecting their varied diets and echolocation behaviors. The presence of bony discontinuities between the premaxilla and maxilla or among the premaxillae is a notable feature of bat orofacial morphology, observed in certain lineages. It is suggested that these unique orofacial morphotypes, not generally found in other mammals, have evolved in relation to dietary adaptations rather than merely for echolocation mode. Until now, the developmental background of the bony discontinuities in the bat orofacial complex has been insufficiently investigated. Here, we present a comparative study of the chondrocranium and epithelial organs in the orofacial complex of three bat species: Cynopterus sphinx , Rhinolophus malayanus , and Vespertilio sinensis . Our observations indicate that the preceding morphogenesis of orofacial cartilage and epithelial structures is remarkably different among these three species. In C. sphinx and V. sinensis , the region forming from the regression of the palatine process of the premaxilla was filled with orofacial cartilage and epithelial structures. We also found that the clefted morphology observed in R. malayanus and V. sinensis was formed via contrastingly divergent developmental processes. Midline clefts among Yangochiroptera have been previously categorized to represent a uniform morphotype, but our study highlights that attributing midline clefts into a singular category should be revisited, advocating for a nuanced categorization of cleft morphology based on their morphogenetic patterns. Further research on the bat orofacial complex may enhance our understanding of bat evolutionary diversification and offer insights into the developmental mechanisms of human cleft palate.

Craniofacial morphology is extremely diversified within bat phylogeny, however growth and development of the palate in bats remains unstudied. The formation of both midline and bilateral orofacial clefts in laryngeally echolocating bats, morphologically similar to the syndromic and non‐syndromic cleft palate in humans, are not well understood. Developmental series of prenatal samples ( n = 128) and adults ( n = 10) of eight bat species (two pteropodids, four rhinolophoids, and two yangochiropterans), and two non‐bat mammals ( Mus musculus and Erinaceus amurensis ), were CT‐scanned and cranial bones forming the upper jaw complex were three‐dimensionally visualised to assess whether differences in palate development can be observed across bat phylogeny. Volumetric data of bones composing the upper jaw complex were measured to quantify palate growth. The premaxilla is relatively reduced in bats compared to other mammals and its shape is heterogeneous depending on the presence and type of orofacial cleft across bat phylogeny. The palatine process of premaxillary bones is lacking in pteropodids and yangochiropterans, whereas the premaxilla is a mobile structure which is only in contact caudally with the maxilla by a fibrous membrane or suture in rhinolophoids. In all bats, maxillary bones progressively extend caudally and palatine bones, in some cases split into three branches, extend caudally so that they are completely fused to another one medially prior to the birth. Ossification of the vomer and fusion of the maxillary and palatine bones occur earlier in rhinolophoids than in pteropodids and yangochiropterans. The vomer ossifies bilaterally from two different ossification centres in yangochiropterans, which is uncommon in other bats and non‐bat mammals. Analysis of ontogenetic allometric trajectories of the upper jaw complex revealed faster development of maxillary, vomer, and palatine bones in yangochiropterans compared to other bats, especially rhinolophoids. Ancestral state reconstruction revealed that yangochiropterans have a higher magnitude of change in ossification rate compared to other bats and E. amurensis a lower magnitude compared to M. musculus and bats. This study provides new evidence of heterochronic shifts in craniofacial development and growth across bat phylogeny that can improve understanding of the developmental differences characterising nasal and oral emission strategies.

Background Isolating phylogenetic signal from morphological data is crucial for accurately merging fossils into the tree of life and for calibrating molecular dating. However, subjective character definition is a major limitation which can introduce biases that mislead phylogenetic inferences and divergence time estimation. The use of quantitative data, e.g., geometric morphometric (GMM; shape) data can allow for more objective integration of morphological data into phylogenetic inference. This systematic review describes the current state of the field in using continuous morphometric data (e.g., GMM data) for phylogenetic reconstruction and assesses the efficacy of these data compared to discrete characters using the PRISMA-EcoEvo v1.0. reporting guideline, and offers some pathways for approaching this task with GMM data. A comprehensive search string yielded 11,123 phylogenetic studies published in English up to Oct 2023 in the Web of Science database. Title and abstract screening removed 10,975 articles, and full-text screening was performed for 132 articles. Of these, a total of twelve articles met final inclusion criteria and were used for downstream analyses. Results Phylogenetic performance was compared between approaches that employed continuous morphometric and discrete morphological data. Overall, the reconstructed phylogenies did not show increased resolution or accuracy (i.e., benchmarked against molecular phylogenies) as continuous data alone or combined with discrete morphological datasets. Conclusions An exhaustive search of the literature for existing empirical continuous data resulted in a total of twelve articles for final inclusion following title/abstract, and full-text screening. Our study was performed under a rigorous framework for systematic reviews, which showed that the lack of available comparisons between discrete and continuous data hinders our understanding of the performance of continuous data. Our study demonstrates the problem surrounding the efficacy of continuous data as remaining relatively intractable despite an exhaustive search, due in part to the difficulty in obtaining relevant comparisons from the literature. Thus, we implore researchers to address this issue with studies that collect discrete and continuous data sets with directly comparable properties (i.e., describing shape, or size). Supplementary Information The online version contains supplementary material available at 10.1186/s12862-024-02313-3.