Juvenile Brachychampsa in concretion from Upper Cretaceous Hell Creek + "Terror Bird" osteohistology + synapsid middle ear and hearing ability

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

Recent non-dino papers:

Free pdf:

Ryan C. Allen, Karen Chin, Mike Zawaski, Joseph J. Bevitt & Wayne Smiglewski (2025)
Determining whether a phosphatic concretion containing a Cretaceous juvenile crocodylian is a coprolite or a non-fecal concretion
Scientific Reports 15: 6436
doi: https://doi.org/10.1038/s41598-025-90032-0
https://www.nature.com/articles/s41598-025-90032-0

Phosphatic concretions in terrestrial settings are often identified as coprolites based upon their biotic contents and high phosphorus levels. However, recent discoveries have shown that non-fecal origins of fossiliferous phosphatic concretions are more common than originally recognized. Confusion about the taphonomic origin of phosphatic concretions can lead to erroneous paleobiological and paleoenvironmental interpretations, so a set of criteria would be useful to evaluate whether a phosphatic concretion is a coprolite. Here we describe a phosphatic concretion containing a small crocodylian from the Upper Cretaceous Hell Creek Formation and assess its origin, formation, and paleobiological implications. We conducted neutron computed tomography (CT) on the skull-bearing portion of the concretion, and analyzed the geochemical composition of the concretion with electron microprobe, µ-XRF, and fusion ICP-OES. In this study, the completeness and distribution of the skeletal elements present a stronger case for a non-fecal origin. This scenario suggests minimal transport after death and deposition. Neutron CT analysis of the crocodylian skull supports its referral to Brachychampsa montana, and allows inferences regarding body length, age, and dietary habits. Although coprolites and non-fecal concretions can be difficult to differentiate, unique features can reflect differences in origin that offer different types of taphonomic and paleobiological information.

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Free pdf:

Jordi Alexis Garcia Marsà, Federico L. Agnolín, Delphine Angst and Eric Buffetaut (2025)
Paleohistological Analysis of “Terror Birds” (Phorusrhacidae, Brontornithidae): Paleobiological Inferences
Diversity 17(3): 153
doi: https://doi.org/10.3390/d17030153
https://www.mdpi.com/1424-2818/17/3/153


Extinct flightless birds of the clades Phorusrhacidae and Brontornithidae are among the most characteristic elements of the South American Cenozoic faunas. Although the anatomy, systematics, paleoecology, and distribution of these birds have been analyzed in some detail, there is not a single work dealing with the osteohistology of these taxa. Herein, we present for the first time paleohistological data for phorusrhacids (Patagornis marshi) and brontornithids (Brontornis burmeisteri). A dense vascularized fibrolamellar matrix and an uninterrupted cortex lacking growth lines indicate similar metabolism and physiological attributes occurring in most extant birds, and they differ from the condition of insular taxa or species living in very stable habitats. This is congruent with recent analyses indicating that phorusrhacids were very active birds lacking insularity-related attributes. It also supports recent growing evidence indicating that these birds’ extinction may be related to climatic and environmental changes rather than being the result of competitive displacement by immigrant placental mammals.

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Savannah L Olroyd & Bjørn T Kopperud (2025)
Allometry of sound reception structures and evidence for a mandibular middle ear in non-mammalian synapsids
Evolution, qpaf041
doi: https://doi.org/10.1093/evolut/qpaf041
https://academic.oup.com/evolut/advance-article-abstract/doi/10.1093/evolut/qpaf041/8035541


The origin of sensory structures provides an excellent framework for studying how constraints and selective pressures affect the evolution of complex features. The evolution of the mammalian middle ear from the jaw hinge of non-mammalian synapsids offers a deep-time perspective on sensory evolution but is limited by a poor understanding of early synapsid hearing. This work tests the hypothesis that the size of the reflected lamina of the angular bone in non-mammalian synapsids followed a strict, negative allometric trend that may be expected for a sound receiver. Allometry is first investigated in the pterygoid bone of chameleons, which was co-opted for hearing in some species and represents a possible analog for the synapsid reflected lamina. Results indicate that chameleons with a pterygoid ear exhibit a similar allometric slope, while species without a pterygoid ear have variable slopes, suggesting an optimum allometric pattern in sound receivers. In the reflected lamina, we find reduced variation around the allometric trend in therocephalians and non-bidentalian anomodonts, and evolutionary modeling suggests constraint in these groups. These results are consistent with a mandibular middle ear in non-mammalian synapsids, adding valuable new insights to the hypothesis that selective pressures for hearing ability were present long before the evolution of the mammalian middle ear.

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