Coelacanth fossil record + non-marine teleost fishes across K-Pg boundary + Upper Cretaceous Kaiparowits Formation skeletal remains +Triassic megamonsoon (free pdfs)
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Ben Creisler
Jul 8, 2025, 5:57:33 PM7/8/25
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Ben Creisler
bcre...@gmail.com
Zhiwei Yuan, Lionel Cavin and Haijun Song (2025)
On the Incompleteness of the Coelacanth Fossil Record
Fossil Studies 3(3): 10
doi: https://doi.org/10.3390/fossils3030010
https://www.mdpi.com/2813-6284/3/3/10
This study conducted a spatiotemporal review of the coelacanth fossil record and explored its distribution and diversity patterns. Coelacanth research can be divided into two distinct periods: the first period, which is based solely on the fossil record, and the second period following the discovery of extant taxa, significantly stimulating research interest. The distribution and research intensity of coelacanth fossils exhibit marked spatial heterogeneity, with Europe and North America being the most extensively studied regions. In contrast, Asia, South America, and Oceania offer substantial potential for future research. Temporally, the coelacanth fossil record also demonstrates significant variation across geological periods, revealing three diversity peaks in the Middle Devonian, Early Triassic, and Late Jurassic, with the Early Triassic peak exhibiting the highest diversity. With the exception of the Late Devonian, Carboniferous, and Late Cretaceous, most periods remain understudied, particularly the Permian, Early Jurassic, and Middle Jurassic, where the record is notably scarce. Integrating the fossil record with phylogenetic analyses enables more robust estimations of coelacanth diversity patterns through deep time. The diversity peak observed in the Middle Devonian is consistent with early burst models of diversification, whereas the Early and Middle Triassic peaks are considered robust, and the Late Jurassic peak may be influenced by taphonomic biases. The low population abundance and limited diversity of coelacanths reduce the number of specimens available for fossilization. The absence of a Cenozoic coelacanth fossil record may be linked to their moderately deep-sea habitat. Future research should prioritize addressing gaps in the fossil record, particularly in Africa, Asia, and Latin America; employing multiple metrics to mitigate sampling biases; and integrating a broader range of taxa into phylogenetic analyses. In contrast to the widespread distribution of the fossil record, extant coelacanths exhibit a restricted distribution, underscoring the urgent need to increase conservation efforts.
Free pdf:
Donald B. Brinkman, Julien D. Divay, David G. DeMar, Jr., and Gregory P. Wilson Mantilla (2025)
Moderate extinctions and slow recovery of non-marine teleost fishes across the Cretaceous–Paleogene boundary, with a systematic appraisal of early Paleocene teleost fishes from Saskatchewan, Canada and Montana, USA.
Palaeontologia Electronica 28(2): a28.
doi: https://doi.org/10.26879/1559
https://palaeo-electronica.org/content/2025/5566-teleost-fishes-across-the-cretaceous-paleogene-boundary
Teleost fishes from the lowermost Paleocene Tullock Member of the Fort Union Formation of Garfield County, Montana, USA, and the Ravenscrag Formation of southern Saskatchewan, Canada, are described and compared with assemblages from the latest Cretaceous Hell Creek Formation of Garfield County, Montana, to analyze the faunal dynamics of freshwater teleost fishes during the Cretaceous-Paleogene mass extinction event. A minimum of 18 early Paleocene operational taxonomic units (OTUs) are recognized with 10 of these being present in the earliest Paleocene (Puercan 1 North American Land Mammal “age”) localities and eight being range-through taxa that are inferred to be present based on their presence in lower and higher horizons. An estimated 27% of the OTUs present during the end of the Cretaceous of the northern Western Interior of North America did not extend into the earliest Paleocene. Further extinctions occurred in successive subintervals of the early Paleocene, resulting in a total loss of 56% of latest Cretaceous taxa by the last subinterval of the early Paleocene (Puercan, Pu3). Rather than a recovery to the levels of richness seen during the latest Cretaceous, a stepwise pattern of decline in taxonomic richness occurred throughout the early Paleocene. Comparison of the early Paleocene assemblages with those of the late Paleocene assemblages from Alberta and Saskatchewan, Canada, indicates that taxonomic richness remained low through the Paleocene. This pattern differs from the one seen in mammals, for which taxonomic richness exceeded latest Cretaceous levels by the Pu3.
=====
Runjian Chu, Huaichun Wu, Jian Zhang, Qiang Fang, Christian Zeeden, Peng Chen, Rukai Zhu, Jingwei Cui, Shihong Zhang, Tianshui Yang & Chengshan Wang (2025)
Orbital eccentricity and internal feedbacks drove the Triassic megamonsoon variability
Scientific Reports 15: 24190
doi: https://doi.org/10.1038/s41598-025-09295-2
https://www.nature.com/articles/s41598-025-09295-2
The evolution of the Triassic megamonsoon was closely linked to Earth’s orbital variations. Despite recognizing secular orbital cycles as a fundamental pacemaker of the megamonsoon, the driving mechanisms remain unclear. Here, we use data-model synthesis to study orbital-scale megamonsoon variability during the Middle Triassic (~ 246–239 Ma). By integrating high-resolution reconstructions of hydrologic fluctuations, obtained from lithological and magnetic susceptibility data series in the lacustrine sediments of the Ordos Basin (Northeast Tethys), with the climate simulations, we identify monsoon cycles in the ~ 20, 100, and 405 kyr Milankovitch bands. Comparisons with other records further reveal an additional eccentricity-related ~ 3.3 Myr orbital cycle in monsoon variabilities, temperature oscillations, carbon cycles, and sea-level changes. Earth system models show the effects of orbital configurations and atmospheric CO₂ concentrations on megamonsoon dynamics, implying threshold responses to solar radiation and the impacts of temperature and sea-level fluctuations on long-term megamonsoon variability. These findings improve our understanding of the interplay between astronomical forcing and feedbacks in shaping orbital-scale monsoon dynamics.
Recent non-dino papers:
Free pdf:
Zhiwei Yuan, Lionel Cavin and Haijun Song (2025)
On the Incompleteness of the Coelacanth Fossil Record
Fossil Studies 3(3): 10
doi: https://doi.org/10.3390/fossils3030010
https://www.mdpi.com/2813-6284/3/3/10
This study conducted a spatiotemporal review of the coelacanth fossil record and explored its distribution and diversity patterns. Coelacanth research can be divided into two distinct periods: the first period, which is based solely on the fossil record, and the second period following the discovery of extant taxa, significantly stimulating research interest. The distribution and research intensity of coelacanth fossils exhibit marked spatial heterogeneity, with Europe and North America being the most extensively studied regions. In contrast, Asia, South America, and Oceania offer substantial potential for future research. Temporally, the coelacanth fossil record also demonstrates significant variation across geological periods, revealing three diversity peaks in the Middle Devonian, Early Triassic, and Late Jurassic, with the Early Triassic peak exhibiting the highest diversity. With the exception of the Late Devonian, Carboniferous, and Late Cretaceous, most periods remain understudied, particularly the Permian, Early Jurassic, and Middle Jurassic, where the record is notably scarce. Integrating the fossil record with phylogenetic analyses enables more robust estimations of coelacanth diversity patterns through deep time. The diversity peak observed in the Middle Devonian is consistent with early burst models of diversification, whereas the Early and Middle Triassic peaks are considered robust, and the Late Jurassic peak may be influenced by taphonomic biases. The low population abundance and limited diversity of coelacanths reduce the number of specimens available for fossilization. The absence of a Cenozoic coelacanth fossil record may be linked to their moderately deep-sea habitat. Future research should prioritize addressing gaps in the fossil record, particularly in Africa, Asia, and Latin America; employing multiple metrics to mitigate sampling biases; and integrating a broader range of taxa into phylogenetic analyses. In contrast to the widespread distribution of the fossil record, extant coelacanths exhibit a restricted distribution, underscoring the urgent need to increase conservation efforts.
=====
Free pdf:
Donald B. Brinkman, Julien D. Divay, David G. DeMar, Jr., and Gregory P. Wilson Mantilla (2025)
Moderate extinctions and slow recovery of non-marine teleost fishes across the Cretaceous–Paleogene boundary, with a systematic appraisal of early Paleocene teleost fishes from Saskatchewan, Canada and Montana, USA.
Palaeontologia Electronica 28(2): a28.
doi: https://doi.org/10.26879/1559
https://palaeo-electronica.org/content/2025/5566-teleost-fishes-across-the-cretaceous-paleogene-boundary
Teleost fishes from the lowermost Paleocene Tullock Member of the Fort Union Formation of Garfield County, Montana, USA, and the Ravenscrag Formation of southern Saskatchewan, Canada, are described and compared with assemblages from the latest Cretaceous Hell Creek Formation of Garfield County, Montana, to analyze the faunal dynamics of freshwater teleost fishes during the Cretaceous-Paleogene mass extinction event. A minimum of 18 early Paleocene operational taxonomic units (OTUs) are recognized with 10 of these being present in the earliest Paleocene (Puercan 1 North American Land Mammal “age”) localities and eight being range-through taxa that are inferred to be present based on their presence in lower and higher horizons. An estimated 27% of the OTUs present during the end of the Cretaceous of the northern Western Interior of North America did not extend into the earliest Paleocene. Further extinctions occurred in successive subintervals of the early Paleocene, resulting in a total loss of 56% of latest Cretaceous taxa by the last subinterval of the early Paleocene (Puercan, Pu3). Rather than a recovery to the levels of richness seen during the latest Cretaceous, a stepwise pattern of decline in taxonomic richness occurred throughout the early Paleocene. Comparison of the early Paleocene assemblages with those of the late Paleocene assemblages from Alberta and Saskatchewan, Canada, indicates that taxonomic richness remained low through the Paleocene. This pattern differs from the one seen in mammals, for which taxonomic richness exceeded latest Cretaceous levels by the Pu3.
=====
Free pdf:
Daigo Yamamura and Celina Suarez (2025)
Vertebrate Skeletal Remains as Paleohydrologic Proxies: Complex Hydrologic Setting in the Upper Cretaceous Kaiparowits Formation
Geosciences 15(7): 262
doi: https://doi.org/10.3390/geosciences15070262
https://www.mdpi.com/2076-3263/15/7/262
The Kaiparowits Formation preserves one of the best fossil records of Cretaceous North America, which provides great insight into the paleoecology. In an effort to investigate the paleohydrology of the Kaiparowits Formation, stable isotope compositions (δ13C, δ18O-carbonate, δ18O-phosphate) of 41 hadrosaur teeth, 27 crocodile teeth, and 35 turtle shell fragments were analyzed. The mean O-isotope compositions of drinking water (δ18Ow) calculated from the O-isotope of bioapatite (phosphate-δ18Op) are −13.76 ± 2.08‰ (SMOW) for hadrosaur, −8.88 ± 2.76‰ (SMOW) for crocodile, and −10.14 ± 2.62‰ (SMOW) for turtle, which strongly reflect niche partitioning. The Kaiparowits formation does not fit the global trend in isotopic compositions of vertebrate skeletal remains from previous studies, which suggests a unique hydrological setting of the Kaiparowits basin. High-elevation runoff from the Mogollon Highlands and sea level fluctuation may have contributed to such a unique paleohydrology.
===
Daigo Yamamura and Celina Suarez (2025)
Vertebrate Skeletal Remains as Paleohydrologic Proxies: Complex Hydrologic Setting in the Upper Cretaceous Kaiparowits Formation
Geosciences 15(7): 262
doi: https://doi.org/10.3390/geosciences15070262
https://www.mdpi.com/2076-3263/15/7/262
The Kaiparowits Formation preserves one of the best fossil records of Cretaceous North America, which provides great insight into the paleoecology. In an effort to investigate the paleohydrology of the Kaiparowits Formation, stable isotope compositions (δ13C, δ18O-carbonate, δ18O-phosphate) of 41 hadrosaur teeth, 27 crocodile teeth, and 35 turtle shell fragments were analyzed. The mean O-isotope compositions of drinking water (δ18Ow) calculated from the O-isotope of bioapatite (phosphate-δ18Op) are −13.76 ± 2.08‰ (SMOW) for hadrosaur, −8.88 ± 2.76‰ (SMOW) for crocodile, and −10.14 ± 2.62‰ (SMOW) for turtle, which strongly reflect niche partitioning. The Kaiparowits formation does not fit the global trend in isotopic compositions of vertebrate skeletal remains from previous studies, which suggests a unique hydrological setting of the Kaiparowits basin. High-elevation runoff from the Mogollon Highlands and sea level fluctuation may have contributed to such a unique paleohydrology.
===
Free pdf:
Runjian Chu, Huaichun Wu, Jian Zhang, Qiang Fang, Christian Zeeden, Peng Chen, Rukai Zhu, Jingwei Cui, Shihong Zhang, Tianshui Yang & Chengshan Wang (2025)
Orbital eccentricity and internal feedbacks drove the Triassic megamonsoon variability
Scientific Reports 15: 24190
doi: https://doi.org/10.1038/s41598-025-09295-2
https://www.nature.com/articles/s41598-025-09295-2
The evolution of the Triassic megamonsoon was closely linked to Earth’s orbital variations. Despite recognizing secular orbital cycles as a fundamental pacemaker of the megamonsoon, the driving mechanisms remain unclear. Here, we use data-model synthesis to study orbital-scale megamonsoon variability during the Middle Triassic (~ 246–239 Ma). By integrating high-resolution reconstructions of hydrologic fluctuations, obtained from lithological and magnetic susceptibility data series in the lacustrine sediments of the Ordos Basin (Northeast Tethys), with the climate simulations, we identify monsoon cycles in the ~ 20, 100, and 405 kyr Milankovitch bands. Comparisons with other records further reveal an additional eccentricity-related ~ 3.3 Myr orbital cycle in monsoon variabilities, temperature oscillations, carbon cycles, and sea-level changes. Earth system models show the effects of orbital configurations and atmospheric CO₂ concentrations on megamonsoon dynamics, implying threshold responses to solar radiation and the impacts of temperature and sea-level fluctuations on long-term megamonsoon variability. These findings improve our understanding of the interplay between astronomical forcing and feedbacks in shaping orbital-scale monsoon dynamics.
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