Paleozoic amniote jaw form and function + turtle visual cortex response + terrestrial trophic systems + Hell Creek river system evolution

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Non-dino papers:

Free pdf:

Jasper Ponstein, Mark J. MacDougall, Joep Schaeffer, Christian F. Kammerer & Jörg Fröbisch (2025)
Mandibular form and function is more disparate in amniotes than in non-amniote tetrapods from the late Palaeozoic.
PeerJ 13:e20243
doi: https://doi.org/10.7717/peerj.20243
https://peerj.com/articles/20243/


Terrestrial tetrapods originated during the Middle Devonian, and the group rapidly diversified throughout the subsequent Carboniferous and Permian periods. Feeding in air rather than water is expected to require changes to tetrapod mandibular form and function. Previous biomechanical studies on jaw evolution, however, found that the increase in functional disparity lagged behind terrestrialisation by approximately 70 Myr, coinciding with the origin of amniotes and herbivory. We expand on a previous dataset composed primarily of non-amniote tetrapods to identify the drivers of this diversification, including representatives of all major amniote clades from the Permo-Carboniferous. First, we measured nine biomechanical traits from 111 tetrapod jaws in medial view. Second, we performed an Elliptical Fourier Analysis on 198 jaws in lateral view and 73 jaws in occlusal view. The first peak in jaw disparity, during the Pennsylvanian, occurs in carnivorous non-amniote tetrapods. However, the jaws of amniotes, particularly those inferred as herbivorous, are consistently more disparate than non-amniote tetrapods from the early Permian, especially in terms of jaw depth, symphysial length and force transmission. Functional and shape disparity of Palaeozoic tetrapod jaws follow a similar pattern that is explained by large-scale faunal turnovers and ecosystem structures.

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Free pdf:

Milan Becker, Nimrod Leberstein, and Mark Shein-Idelson (2025)
View-invariant representations in ancestral cortex
Science Advances 11(48): eady9659
DOI:10.1126/sciadv.ady965
https://www.science.org/doi/10.1126/sciadv.ady9659


A multilayered, thalamorecipient visual cortex emerged ~320 million years ago in stem amniotes. Despite its importance for understanding the evolution of cortical computation, its function remains unknown. We recorded visually evoked responses in the dorsal cortex of behaving turtles, considered a mammalian neocortex homolog. Using a spatial oddball paradigm, we found tuning to stimuli in deviant positions alongside adaptation to standard positions within the visual field. Eye tracking demonstrated that responses remained spatially selective despite gaze shifts altering retinal stimulus position. Thus, the turtle cortex encodes unexpected visual stimuli using computations invariant to retinal position, a property previously observed only in higher mammalian cortices. These results indicate that invariance computations preceded the evolution of local filtering computations in mammalian primary cortices, pointing to a previously unidentified function for ancestral cortices. They also challenge hierarchical models of invariance computations, which assume that invariance is built from low-level features across multiple processing steps.

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Free pdf:

Luis F. Camacho and Miguel B. Araujo (2025)
Global evidence of non-pyramidal and uniform ratios of animal diversity across terrestrial trophic levels
Proceedings of the Royal Society B: Biological Sciences 292(2059): 20252335
doi: https://doi.org/10.1098/rspb.2025.2335
https://royalsocietypublishing.org/doi/10.1098/rspb.2025.2335

Free pdf:
https://royalsocietypublishing.org/doi/epdf/10.1098/rspb.2025.2335


Thermodynamics imposes a well-established pyramidal distribution of energy availability across trophic levels, but whether species richness follows the same pattern remains unclear. In this study, we examined species richness across trophic groups for all known terrestrial tetrapod and arthropod species, representing over 90% of Earth’s terrestrial animal diversity. By categorizing species into fundamental trophic levels, we found that 46% are primary consumers (feeding on plants), 43% are higher-level consumers (feeding on primary consumers) and 11% are mixed consumers (generalists). Further analysis of global community trophic structures in mammals and birds uncovered a consistent ratio of species richness across trophic levels, independent of geographical location or total species richness. We propose that this non-pyramidal distribution of diversity arises from higher ecological differentiation among species at higher trophic levels, which may offset their greater extinction risk associated with smaller populations. This process could generate uniform trophic structures if primarily driven by mechanics intrinsic to trophic positions and their interactions rather than specific environmental characteristics. Such intrinsic mechanisms may ultimately influence diversity across trophic levels and the eco-evolutionary dynamics structuring ecological networks.

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Caroline E.J. Hasler & Paul R. Renne (2025)
Elongated sandstone concretions record river system evolution across the Cretaceous-Paleogene boundary, Montana, USA
GSA Bulletin (advance online publication)
doi: https://doi.org/10.1130/B38532.1
https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B38532.1/670460/Elongated-sandstone-concretions-record-river


The Cretaceous−Paleogene (K-Pg) extinction caused significant environmental upheaval, including the disappearance of non-avian dinosaurs and widespread disruption of ecosystems. The Hell Creek and Fort Union formations in the upper Great Plains of North America preserve a record of environmental change across the K-Pg boundary (KPB). Sedimentological studies suggest that the Hell Creek Formation represents a well-drained floodplain, with increased standing water leading to the formation of ponds and peat bogs close to the KPB. This shift has been attributed to the disruption of river systems by short-term extinction-driven flooding in the Western Interior. To test this, we analyze ∼2900 paleocurrent measurements from elongate concretions mapped over ∼5000 km2 in the Hell Creek area of eastern Montana, USA. These measurements, combined with previously published chronostratigraphic constraints, allow us to trace river system evolution over time. Paleocurrents shift from a uniform NW-SE direction to a chaotic and later bimodal pattern ∼400 k.y. after the KPB, but no major shifts occur at the KPB itself. Additionally, we develop a method to identify meandering rivers based on paleocurrent distributions and use it to assess river planform changes. Environmental crises have been suggested to cause transitions from meandering to braided rivers, but we find no evidence of such a change. This suggests that the K-Pg extinction did not significantly disrupt regional drainage or river systems in the Hell Creek area. The results demonstrate the potential of remote sensing for reconstructing paleoriver dynamics and suggest that some river systems may be stable across mass extinction events.

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