Biology subjects

Ksepka, D. T.

Publications and source records attributed to Ksepka, D. T..

3 recordsLinked to original sources

bioRxiv2025

Mandibular morphology clarifies phylogenetic relationships near the origin of crown birds

BackgroundThe phylogenetic relationships of fossil birds near the origin of the avian crown group remain debated, in part due to a limited amount of character evidence from incomplete fossils. The avian lower jaw provides a potentially rich source of additional character data, yet fusion of the individual bony elements composing the avian post-dentary complex has impeded efforts to explore its phylogenetic signal. Here, we use high-resolution {micro}CT-scanning to separate the individual bony elements of the mandibles of several immature crown birds and key fossil taxa, and use those data to assess support for alternative phylogenetic hypotheses for fossils near the origin of crown birds. ResultsWe find that evidence from Asteriornis fails to support interpretations of derived mandibular similarities with palaeognaths, and instead strongly favours galloanseran, and specifically galliform, affinities. Our results also illustrate striking similarities in the architecture of the lower jaws between the toothed ornithurine Ichthyornis, Pelagornithidae and Vegavis, which, in addition to the absence of derived features linking them to Galloanserae, highlights questions regarding the phylogenetic position of these perennially controversial taxa. ConclusionsOur data reveal new insight into patterns of morphological evolution near the origin of the avian crown group while raising new phylogenetic questions, emphasising the potential untapped value of detailed comparative investigations of morphological complexes such as the post-dentary complex of the mandible for informing the early evolutionary history of crown birds.

paleontology↗

bioRxiv2025

Efficient Inference of Macrophylogenies: Insights from the Avian Tree of Life

The exponential growth of molecular sequence data over the past decade has enabled the construction of numerous clade-specific phylogenies encompassing hundreds or thousands of taxa. These independent studies often include overlapping data, presenting a unique opportunity to build macrophylogenies (phylogenies sampling > 1,000 taxa) for entire classes across the Tree of Life. However, the inference of large trees remains constrained by logistical, computational, and methodological challenges. The Avian Tree of Life provides an ideal model for evaluating strategies to robustly infer macrophylogenies from intersecting datasets derived from smaller studies. In this study, we leveraged a comprehensive resource of sequence capture datasets to evaluate the phylogenetic accuracy and computational costs of four methodological approaches: (1) supermatrix approaches using concatenation, including the "fast" maximum likelihood (ML) methods, (2) filtering datasets to reduce heterogeneity, (3) supertree estimation based on published phylogenomic trees, and (4) a "divide-and-conquer" strategy, wherein smaller ML trees were estimated and subsequently combined using a supertree approach. Additionally, we examined the impact of these methods on divergence time estimation using a dataset that includes newly vetted fossil calibrations for the Avian Tree of Life. Our findings highlight that recently developed fast tree search approaches offer a reasonable compromise between computational efficiency and phylogenetic accuracy, facilitating inference of macrophylogenies.

evolutionary biology↗

bioRxiv2023

Taphonomic damage obfuscates interpretation of the retroarticular region of the Asteriornis mandible

Asteriornis maastrichtensis, from the latest Cretaceous of Belgium, is among the oldest known crown bird fossils, and its three-dimensionally preserved skull provides the most substantial insights into the cranial morphology of early crown birds to date. Phylogenetic analyses recovered Asteriornis as a total-group member of Galloanserae (the clade uniting Galliformes and Anseriformes. One important feature supporting this placement was enlargement of the retroarticular processes, which form elongate caudal extensions of the mandible in extant Galloanserae. Here, we reinterpret the jaw of Asteriornis and illustrate that the caudalmost portion of the mandibles are in fact not preserved. Instead, the caudal extremities of both the left and right mandibular rami extend to the surface of the fossil block containing the holotype skull, where they have eroded away. The originally identified retroarticular process of the right mandible--which exhibits a morphology and orientation strikingly similar to the retroarticular processes of certain extant and fossil galloanserans, including the early Palaeogene total-clade anseriforms Conflicto and Nettapterornis--instead represents a twisted and caudally displaced medial process. Nonetheless, anatomical comparisons with extant taxa reveal that we are unable to exclude the possibility that Asteriornis exhibited robust retroarticular processes comparable to those of extant Galloanserae. In light of the reinterpreted morphology of the Asteriornis mandible, we update the original anatomical character matrix used to investigate its phylogenetic relationships, and our revised phylogenetic analyses continue to support its position as a total-group galloanseran, as initially interpreted. We demonstrate additional morphological traits of the mandible supporting this phylogenetic position and provide new data on the nature and distribution of retroarticular processes among early crown birds.

paleontology↗