Dinosaur-bearing Upper Cretaceous Zhengyang Formation, China + Cretaceous theropod and sauropod tracks from Mexico + Cynognathus and Diademodon maxillary canal + Boverisuchus osteology + more
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Ben Creisler
Jul 20, 2026, 7:04:42 PM (3 days ago) Jul 20
to DinosaurMa...@googlegroups.com
Ben Creisler
Catching up on some recent papers:
Situated within the southwestern segment of Chongqing, the Zhengyang Basin formed one of the intermountain basins within the Yanshanian orogenic belt that developed during the Late Cretaceous. The Zhengyang Basin preserves a > 100 m-thick Upper Cretaceous terrestrial successions, named the Zhengyang Formation characterized by debris-flow deposits and fluvial-lacustrine units. Recently, abundant dinosaur fossils have been collected from this formation, including hadrosaurs, titanosaurs, and theropods, providing substantial evidence of an exceptional middle Late Cretaceous dinosaur fauna in Southwest China. We herein report detailed stratigraphic architecture, dinosaur fossil assemblage, sedimentary and palaeoenvironmental features of the Zhengyang Formation in the Zhengyang Basin. The evidence suggests that the dinosaurs lived in a restricted intermountain basin, of which the palaeoclimate was significantly influenced by a transition from overall humid to arid condition. Our data lead to new evaluation of early Late Cretaceous dinosaur evolution, and provide new clues for investigation on the contemporary terrestrial palaeoenvironmental and palaeoclimatic features in the mid-low latitude area of East Asia. The stratigraphic features of the Zhengyang Formation also provide new insights into showing lateral correlation of the Late Cretaceous terrestrial successions in East Asia.
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Alan F. Celestino-Hernández, Diego E. Lozano-Carmona, Francisco J. Jiménez-Moreno & Ricardo Agustín-Serrano (2026)
Description of New Theropoda and Sauropoda Trackways from the San Juan Raya Formation (Early Cretaceous) in Santa Ana Teloxtoc and San Martín Atexcal, Puebla, Mexico.
Paleontología Mexicana 15(2): 373–396. (in Spanish)
doi: https://doi.org/10.22201/igl.05437652e.2026.15.2.442
https://paleontologiamexicana.geologia.unam.mx/index.php/paleontologia/article/view/442
Free pdf:
https://paleontologiamexicana.geologia.unam.mx/index.php/paleontologia/article/view/442/698
Four new records of dinosaur ichnites from the suborders Theropoda and Sauropoda are described in the San Juan Raya Formation (Early Cretaceous). These were located in the Barranca El Salitrillo, Santa Ana Teloxtoc, municipality of Tehuacán and in the Magdalena River, municipality of San Martín Atexcal in the southeast of the state of Puebla. The photogrammetry technique was used for the digital recording of each dinosaur footprint. The photographs were processed with free software programs, first with VisualFm v. 0.5.26 where the 3D models were obtained, then they were processed with the Blender v. 4.2 and Paraview v. 5.13 programs. This allowed for a more detailed observation of the morphological characteristics of the ichnites. The ImageJ v. 1.53t program was used to obtain the morphometric data and perform the description. Subsequently, paleobiological estimates were made of the organisms that produced each ichnite, for example, hip height (acetabular), length and body mass. The new Saurischia records found in the Barranca El Salitrillo locality include the first records of an ichnite generated by a small Sauropoda and two ichnites of Theropoda, one of them corresponding to an intermediate-sized individual and the other to a small-sized individual. The latter corresponds to a tridactyl ichnite no larger than seven centimeters in length. In addition, a new ichnite is reported in the Río Magdalena locality that would correspond to a medium-sized Theropoda individual with a tendency towards megatheropoda. These records contribute to the complex dinosaur ichnofauna of the San Juan Raya Formation.
Julien Benoit, Valentin Buffa & Michael O. Day (2026)
The maxillary canal in Cynognathus and Diademodon (Cynodontia, Cynognathia)
The Science of Nature 113(4): 84
https://doi.org/10.1007/s00114-026-02133-z
https://link.springer.com/article/10.1007/s00114-026-02133-z
Boverisuchus, a mid-sized eusuchian crocodyliform from the middle Eocene of Europe and North America, has long been regarded as more terrestrial than extant crocodylians and is often portrayed as one of the apex predators in Laurasian terrestrial ecosystems during the middle Eocene. Although Boverisuchus has been studied extensively since the nineteenth century, its skeletal osteology warranted re-examination based on three-dimensionally preserved materials to better understand its anatomy, function, and ecology. Our revised description of the North American Boverisuchus vorax provides new insights into previously poorly known aspects of the postcranium, including the configuration of the manus and pes. Comparative analyses of skeletal proportions incorporating phylogenetically informed allometric corrections indicate that B. vorax possesses elongated fore- and hindlimbs, elongated proximal carpals, and shortened metacarpals and digits—features that enhance the stance phase support and propulsive capacities, increase stride lengths, and reduce the cost of leg swing. The short, hoof-like terminal phalanges are integral to the overall shortening of the manual and pedal phalanges, reducing distal limb mass and improving swing phase energetics at the expense of stability. Additionally, the diagonal accessory keels and ridges on the paravertebral osteoderms likely functioned to resist torsional stresses on the trunk while trotting. Taken together, these skeletal proportions and postcranial specializations suggest increased terrestriality and improved locomotor capabilities in B. vorax.
Sixty-six million years ago, at the Cretaceous-Paleogene boundary (K/Pg boundary), a meteorite impacted the Earth causing the mass extinction of marine and terrestrial species. It has been suggested that volcanism was more important. Linked to the extinction is a change in the cycling of carbon. We have investigated the stable isotopes of carbon preserved in coals from the Western Interior Basin of North America in order to establish how long the cycling of carbon may have been disrupted. These coals capture a terrestrial archive of climate. Chronological constraints show that the change in carbon cycling following the impact lasted just a few tens of thousands of years and recovered in Paleogene times. Our findings align closely with some, but not all, marine records. The cause of a short duration carbon cycling event at the K/Pg boundary is compatible with events associated with the meteorite impact.
Hui Dai, Jun Wang, Liang-Dong Luo, Qian-Ru Wen, Su-Chin Chang, Yu Lin, Ming Xiao & Hai Xing (2026)
Stratigraphy, sedimentology, and palaeoenvironment of dinosaur-bearing Upper Cretaceous Zhengyang Formation in Zhengyang Basin, Chongqing, Southwest China
Palaeoworld (advance online publication)
https://doi.org/10.1016/j.palwor.2026.201158
https://www.sciencedirect.com/science/article/abs/pii/S1871174X26000934
Stratigraphy, sedimentology, and palaeoenvironment of dinosaur-bearing Upper Cretaceous Zhengyang Formation in Zhengyang Basin, Chongqing, Southwest China
Palaeoworld (advance online publication)
https://doi.org/10.1016/j.palwor.2026.201158
https://www.sciencedirect.com/science/article/abs/pii/S1871174X26000934
Situated within the southwestern segment of Chongqing, the Zhengyang Basin formed one of the intermountain basins within the Yanshanian orogenic belt that developed during the Late Cretaceous. The Zhengyang Basin preserves a > 100 m-thick Upper Cretaceous terrestrial successions, named the Zhengyang Formation characterized by debris-flow deposits and fluvial-lacustrine units. Recently, abundant dinosaur fossils have been collected from this formation, including hadrosaurs, titanosaurs, and theropods, providing substantial evidence of an exceptional middle Late Cretaceous dinosaur fauna in Southwest China. We herein report detailed stratigraphic architecture, dinosaur fossil assemblage, sedimentary and palaeoenvironmental features of the Zhengyang Formation in the Zhengyang Basin. The evidence suggests that the dinosaurs lived in a restricted intermountain basin, of which the palaeoclimate was significantly influenced by a transition from overall humid to arid condition. Our data lead to new evaluation of early Late Cretaceous dinosaur evolution, and provide new clues for investigation on the contemporary terrestrial palaeoenvironmental and palaeoclimatic features in the mid-low latitude area of East Asia. The stratigraphic features of the Zhengyang Formation also provide new insights into showing lateral correlation of the Late Cretaceous terrestrial successions in East Asia.
=====
Free pdf:
Alan F. Celestino-Hernández, Diego E. Lozano-Carmona, Francisco J. Jiménez-Moreno & Ricardo Agustín-Serrano (2026)
Description of New Theropoda and Sauropoda Trackways from the San Juan Raya Formation (Early Cretaceous) in Santa Ana Teloxtoc and San Martín Atexcal, Puebla, Mexico.
Paleontología Mexicana 15(2): 373–396. (in Spanish)
doi: https://doi.org/10.22201/igl.05437652e.2026.15.2.442
https://paleontologiamexicana.geologia.unam.mx/index.php/paleontologia/article/view/442
Free pdf:
https://paleontologiamexicana.geologia.unam.mx/index.php/paleontologia/article/view/442/698
Four new records of dinosaur ichnites from the suborders Theropoda and Sauropoda are described in the San Juan Raya Formation (Early Cretaceous). These were located in the Barranca El Salitrillo, Santa Ana Teloxtoc, municipality of Tehuacán and in the Magdalena River, municipality of San Martín Atexcal in the southeast of the state of Puebla. The photogrammetry technique was used for the digital recording of each dinosaur footprint. The photographs were processed with free software programs, first with VisualFm v. 0.5.26 where the 3D models were obtained, then they were processed with the Blender v. 4.2 and Paraview v. 5.13 programs. This allowed for a more detailed observation of the morphological characteristics of the ichnites. The ImageJ v. 1.53t program was used to obtain the morphometric data and perform the description. Subsequently, paleobiological estimates were made of the organisms that produced each ichnite, for example, hip height (acetabular), length and body mass. The new Saurischia records found in the Barranca El Salitrillo locality include the first records of an ichnite generated by a small Sauropoda and two ichnites of Theropoda, one of them corresponding to an intermediate-sized individual and the other to a small-sized individual. The latter corresponds to a tridactyl ichnite no larger than seven centimeters in length. In addition, a new ichnite is reported in the Río Magdalena locality that would correspond to a medium-sized Theropoda individual with a tendency towards megatheropoda. These records contribute to the complex dinosaur ichnofauna of the San Juan Raya Formation.
====
====
Free pdf:
Julien Benoit, Valentin Buffa & Michael O. Day (2026)
The maxillary canal in Cynognathus and Diademodon (Cynodontia, Cynognathia)
The Science of Nature 113(4): 84
https://doi.org/10.1007/s00114-026-02133-z
https://link.springer.com/article/10.1007/s00114-026-02133-z
The maxillary canal system in Cynognathus and Diademodon is described. The hypothesis that expansion of the maxillary sinus represents a synapomorphy of the clade Cynognathia is supported. A trend towards the reduction of the inferior palpebral ramus is proposed.
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Free pdf:
Haibing Wang, Neal Anthwal, Shuo Wang & Yuan-Qing Wang (2026)
Evolutionary transformations of the ossified Meckelian cartilage in mammaliaforms
EvoDevo 17: 11
doi: https://doi.org/10.1186/s13227-026-00265-x
https://link.springer.com/article/10.1186/s13227-026-00265-x
Developmental and fossil evidence shows that the mammalian Meckelian cartilage plays a transient but crucial role in forming both the mandible and the middle ear. However, despite its broad occurrence as the Meckelian groove or ossified Meckelian cartilage in Mesozoic mammaliaforms, the evolutionary trajectory of the ossified Meckelian cartilage remains poorly understood. Here, we report the middle ear of the Early Cretaceous eutherian Cokotherium and integrate paleontological and developmental data to reconstruct the evolution of the Meckelian cartilage. Fossil evidence from the Early Cretaceous eutherian Cokotherium reveals a gracile, posteriorly confined ossified Meckelian cartilage with no substantial connection to the middle ear. We propose two evolutionary trajectories of the reduction of the Meckelian cartilage in early mammaliaforms, featured by different morphological configurations of the Meckelian cartilage and the middle ear bones. Comparisons with developmental data in extant mammals suggest that this evolutionary sequence mirrors the ontogenetic fate of the Meckelian cartilage. The ossified Meckelian cartilage likely originated in response to mandibular miniaturization during the origination of mammaliaforms, functioning as a temporary structural stabilizer linking the middle ear and mandible. The major morphological transformations of the ossified Meckelian cartilage thus reflect a stepwise pattern toward ear detachment over phylogeny.
Haibing Wang, Neal Anthwal, Shuo Wang & Yuan-Qing Wang (2026)
Evolutionary transformations of the ossified Meckelian cartilage in mammaliaforms
EvoDevo 17: 11
doi: https://doi.org/10.1186/s13227-026-00265-x
https://link.springer.com/article/10.1186/s13227-026-00265-x
Developmental and fossil evidence shows that the mammalian Meckelian cartilage plays a transient but crucial role in forming both the mandible and the middle ear. However, despite its broad occurrence as the Meckelian groove or ossified Meckelian cartilage in Mesozoic mammaliaforms, the evolutionary trajectory of the ossified Meckelian cartilage remains poorly understood. Here, we report the middle ear of the Early Cretaceous eutherian Cokotherium and integrate paleontological and developmental data to reconstruct the evolution of the Meckelian cartilage. Fossil evidence from the Early Cretaceous eutherian Cokotherium reveals a gracile, posteriorly confined ossified Meckelian cartilage with no substantial connection to the middle ear. We propose two evolutionary trajectories of the reduction of the Meckelian cartilage in early mammaliaforms, featured by different morphological configurations of the Meckelian cartilage and the middle ear bones. Comparisons with developmental data in extant mammals suggest that this evolutionary sequence mirrors the ontogenetic fate of the Meckelian cartilage. The ossified Meckelian cartilage likely originated in response to mandibular miniaturization during the origination of mammaliaforms, functioning as a temporary structural stabilizer linking the middle ear and mandible. The major morphological transformations of the ossified Meckelian cartilage thus reflect a stepwise pattern toward ear detachment over phylogeny.
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Masaya Iijima & Susumu Tomiya (2026)
Postcranial osteology of Boverisuchus vorax from the middle Eocene of Wyoming, USA: Implications for terrestrial adaptation in eusuchian crocodyliforms
Journal of Anatomy (advance online publication)
doi: https://doi.org/10.1111/joa.70206
https://onlinelibrary.wiley.com/doi/10.1111/joa.70206
Postcranial osteology of Boverisuchus vorax from the middle Eocene of Wyoming, USA: Implications for terrestrial adaptation in eusuchian crocodyliforms
Journal of Anatomy (advance online publication)
doi: https://doi.org/10.1111/joa.70206
https://onlinelibrary.wiley.com/doi/10.1111/joa.70206
Boverisuchus, a mid-sized eusuchian crocodyliform from the middle Eocene of Europe and North America, has long been regarded as more terrestrial than extant crocodylians and is often portrayed as one of the apex predators in Laurasian terrestrial ecosystems during the middle Eocene. Although Boverisuchus has been studied extensively since the nineteenth century, its skeletal osteology warranted re-examination based on three-dimensionally preserved materials to better understand its anatomy, function, and ecology. Our revised description of the North American Boverisuchus vorax provides new insights into previously poorly known aspects of the postcranium, including the configuration of the manus and pes. Comparative analyses of skeletal proportions incorporating phylogenetically informed allometric corrections indicate that B. vorax possesses elongated fore- and hindlimbs, elongated proximal carpals, and shortened metacarpals and digits—features that enhance the stance phase support and propulsive capacities, increase stride lengths, and reduce the cost of leg swing. The short, hoof-like terminal phalanges are integral to the overall shortening of the manual and pedal phalanges, reducing distal limb mass and improving swing phase energetics at the expense of stability. Additionally, the diagonal accessory keels and ridges on the paravertebral osteoderms likely functioned to resist torsional stresses on the trunk while trotting. Taken together, these skeletal proportions and postcranial specializations suggest increased terrestriality and improved locomotor capabilities in B. vorax.
====
====
Free pdf:
Gregory D. Price, Rhodri M. Jerrett, Lauren K. O'Connor, Emily Dearing Crampton-Flood, Bart E. van Dongen, Sabine K. Lengger & Marc Davies (2026)
Correlating High-Resolution Terrestrial Organic Carbon Isotope Records Across the Cretaceous-Paleogene Boundary
Paleoceanography and Paleoclimatology 41(7): e2025PA005349
doi: https://doi.org/10.1029/2025PA005349
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025PA005349
Free pdf:
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025PA005349
The Cretaceous–Paleogene boundary (∼66 million years ago) represents the most recent mass extinction event when an estimated 75% of all species became extinct, including all non-avian dinosaurs. Here we focus on the stable carbon isotope (δ13C) analysis of coal and coaly sediments across the terrestrial K/Pg boundary from 10 sites, between 42 and 64°N, USA and Canada. Our δ13C data set shows a statistically significant positive correlation with paleolatitude that we interpret as a consequence of our lower latitude sites being relatively warmer and more humid than our higher latitude sites. Temporally, our data indicates that the K/Pg boundary event is represented by a unique carbon isotope shift that can be readily separated from background excursions through the latest Maastrichtian and earliest Paleogene. This excursion reaches a minimum several centimeters above the K/Pg boundary. Published geochronological constraints on our data suggest the observed carbon isotope excursion at the K/Pg boundary lasted between 10 and 36 kyr and possibly outlasted the fall-out of material injected into the atmosphere by bolide impact. Such a short duration for the K/Pg negative excursion contrasts with some marine records and in this respect may be more related to shallow marine or neritic zone responses to global sea-level and/or climatic change resulting in shorter-lived localized or regional water column deoxygenation. Notably, a short duration negative excursion at the K/Pg is compatible with events associated with the Chicxulub impact.
Plain Language Summary
Gregory D. Price, Rhodri M. Jerrett, Lauren K. O'Connor, Emily Dearing Crampton-Flood, Bart E. van Dongen, Sabine K. Lengger & Marc Davies (2026)
Correlating High-Resolution Terrestrial Organic Carbon Isotope Records Across the Cretaceous-Paleogene Boundary
Paleoceanography and Paleoclimatology 41(7): e2025PA005349
doi: https://doi.org/10.1029/2025PA005349
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025PA005349
Free pdf:
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025PA005349
The Cretaceous–Paleogene boundary (∼66 million years ago) represents the most recent mass extinction event when an estimated 75% of all species became extinct, including all non-avian dinosaurs. Here we focus on the stable carbon isotope (δ13C) analysis of coal and coaly sediments across the terrestrial K/Pg boundary from 10 sites, between 42 and 64°N, USA and Canada. Our δ13C data set shows a statistically significant positive correlation with paleolatitude that we interpret as a consequence of our lower latitude sites being relatively warmer and more humid than our higher latitude sites. Temporally, our data indicates that the K/Pg boundary event is represented by a unique carbon isotope shift that can be readily separated from background excursions through the latest Maastrichtian and earliest Paleogene. This excursion reaches a minimum several centimeters above the K/Pg boundary. Published geochronological constraints on our data suggest the observed carbon isotope excursion at the K/Pg boundary lasted between 10 and 36 kyr and possibly outlasted the fall-out of material injected into the atmosphere by bolide impact. Such a short duration for the K/Pg negative excursion contrasts with some marine records and in this respect may be more related to shallow marine or neritic zone responses to global sea-level and/or climatic change resulting in shorter-lived localized or regional water column deoxygenation. Notably, a short duration negative excursion at the K/Pg is compatible with events associated with the Chicxulub impact.
Plain Language Summary
Sixty-six million years ago, at the Cretaceous-Paleogene boundary (K/Pg boundary), a meteorite impacted the Earth causing the mass extinction of marine and terrestrial species. It has been suggested that volcanism was more important. Linked to the extinction is a change in the cycling of carbon. We have investigated the stable isotopes of carbon preserved in coals from the Western Interior Basin of North America in order to establish how long the cycling of carbon may have been disrupted. These coals capture a terrestrial archive of climate. Chronological constraints show that the change in carbon cycling following the impact lasted just a few tens of thousands of years and recovered in Paleogene times. Our findings align closely with some, but not all, marine records. The cause of a short duration carbon cycling event at the K/Pg boundary is compatible with events associated with the meteorite impact.
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