Arctobatrachus, new giant plagiosaurid temnospondyl from Triassic of Norway + turtle diversification + Candeleros and Huincul Formations redated + marine ecosystem changes prior to and across the Permian−Triassic extinctionformations,
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Ben Creisler
Jul 31, 2026, 2:04:50 PM (6 days ago) Jul 31
to DinosaurMa...@googlegroups.com
Ben Creisler
Some recent papers:
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Free pdf:
Zhongning Zhao, Chad Keates, J. Paul Grobler, Phillip. A. Bester, Stephanus Riekert & Neil Heideman (2026)
Climate, Continental Breakup and Habitat Shape Global Diversification and Biogeography of Turtles (Testudines)
Journal of Biogeography 53(7): e70314
doi: https://doi.org/10.1111/jbi.70314
https://onlinelibrary.wiley.com/doi/10.1111/jbi.70314
Evaluate the relative contributions of palaeotemperature, palaeogeographic reconfiguration, and habitat heterogeneity to the diversification and biogeographic history of turtles (Order Testudines) from the Triassic to the present.
Location and Time Period
Global; Triassic–Recent.
Taxa
Extant Testudines (time-calibrated phylogeny sampling ~286 species).
Methods
We combined a near-complete, time-calibrated phylogeny with complementary macroevolutionary and biogeographic methods. Diversification dynamics were explored using time- and temperature-dependent models (RPANDA), rate-shift analyses (BAMM), and state- and geography-dependent frameworks (GeoHiSSE). Historical ranges were inferred with multiple BioGeoBEARS models. Associations between reconstructed speciation rates and independent palaeotemperature records were tested using Pearson's correlation and detrended cross-correlation analysis (DCCA). Habitat categories (aquatic, amphibious, terrestrial) were coded for all taxa and explicitly incorporated into state-dependent models to assess their influence on diversification dynamics.
Results
Diversification dynamics of Testudines are consistent with interacting effects of palaeoclimate, plate tectonics and habitat. Testudines' diversification positively tracks palaeotemperature overall, but the sign and strength are clade-specific: some lineages speciate more in cooler intervals, others in warmer ones. Ancestral-range reconstructions identify multiple well-supported range shifts and vicariance events that are temporally concordant with major episodes of continental fragmentation. State-dependent analyses recover distinct diversification regimes among aquatic, amphibious and terrestrial lineages, indicating that habitat affinity modulates macroevolutionary responses to climatic and tectonic forcing.
Main Conclusions
No single factor alone explains turtle diversification through deep time. Instead, climatic transitions (both cooling and warming), tectonic reconfiguration of landmasses, and habitat-specific ecology and dispersal capacity were associated with the timing and geography of lineage accumulation in Testudines. Our results indicate that the refugial hypothesis is not universally supported across Testudines. Instead, support is lineage dependent, with some clades diversifying during cooler intervals and others during warmer periods. Moreover, the results indicate that habitat heterogeneity has played a key role in promoting speciation across the group.
Ignacio J. Maniel, Rafael Almeida, David L. Kimbrough, G. Susana de la Puente, Alberto C. Garrido, Flavio Bellardini & J.Brian Mahoney (2026)
Albian zircon U-Pb crystallization ages from tuff beds in the Candeleros and Huincul formations, Neuquén Basin, Argentina
Gondwana Research (advance online publication)
doi: https://doi.org/10.1016/j.gr.2026.06.020
https://www.sciencedirect.com/science/article/pii/S1342937X26002005
Highlights
The dinosaur-rich Candeleros and Huincul Formations are early Albian in age rather than Cenomanian.
This adjustment in age impacts the genus richness patterns of fossils for the Cretaceous of South America and aligns it with the rest of the world.
The new age confirms the diachronous (northward-younging) development of fold-thrust belts along the compressive Andean margin.
Abstract
New U-Pb zircon laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) ages from airfall tuff beds in the dinosaur-rich nonmarine Candeleros Formation (111.4 ± 1.1 Ma) and overlying Huincul Formation (106.8 ± 2.2 Ma) in the Neuquén Basin of Argentina indicate Albian ages for both stratigraphic units. Three widely separated volcanogenic sandstones collected from basal Candeleros Formation strata ∼ 200 km north of the dated Candeleros airfall ash bed contain statistically indistinguishable clusters of young detrital zircon grains that confirm an early Albian (∼111 Ma) age for basal Candeleros strata across the entire Neuquén Basin. Depositionally synchronous zircon, as seen here in basal Candeleros strata, is a widespread and well-documented feature of retroarc basin assemblages adjacent to active volcanic arcs. The new Albian ages for the Candeleros and Huincul formations require a shift in the age of two of the six major tetrapod assemblages defined for the Neuquén Basin by ∼ 10–15 Myr and prompt a broad reevaluation of fossil assemblages and correlations across the Early-Late Cretaceous boundary, which are critical for the study of the evolution and diversification of Patagonian faunas. The early Albian Candeleros Formation is correlated here to the Cerro Barcino Formation of the dinosaur-bearing Chubut Group 500 km to the south of the Neuquén Basin. This correlation resolves formerly confounding biostratigraphic correlation between these two areas. The new ages also place constraints on the timing of Andean fold and thrust belt inception and further indicate that pedogenic contrasts between the Candeleros and Huincul formations reflect the emergence of global climate from cooler conditions toward warmer Greenhouse World conditions broadly characteristic of the mid-Cretaceous.
Stella Z. Buchwald, Daniel Birgel, Evelyn Kustatscher, Herwig Prinoth, Francesca Galasso, Baran Karapunar, Anja B. Frank, Mónica Alejandra Gómez Correa, Niko Lahajnar, Jörn Peckmann & William J. Foster (2026)
Molecular fossils record shallow marine ecosystem changes prior to and across the Permian−Triassic mass extinction in the Dolomites (Italy)
GSA Bulletin (2026)
DOI: https://doi.org/10.1130/B39055.1
https://pubs.geoscienceworld.org/gsa/gsabulletin/article/doi/10.1130/B39055.1/734243/Molecular-fossils-record-shallow-marine-ecosystem
The Permian−Triassic mass extinction, the most severe biotic crisis of the Phanerozoic, has been linked to environmental perturbations triggered by the eruptions of the Siberian Traps Large Igneous Province. However, several of these perturbations have previously been demonstrated to have started several hundred thousand of years before the main extinction phase. To explore this timing and its ecological implications, we analyzed molecular fossils across the Permian−Triassic transition in two shallow marine carbonate ramp sections in the tropical Tethys Ocean of the Dolomites (northern Italy). Both the shallower (Siusi/Seis) and the deeper (Seres) settings record a sudden increase in polycyclic aromatic hydrocarbons, including pyrene and coronene, just above the extinction interval. These compounds probably originated from the combustion of organic-rich sedimentary rocks during Siberian Traps sill emplacement and were subsequently distributed across the study area. Redox-sensitive and source-indicative molecular fossil indices, such as pristane/phytane (Pr/Ph), the terrigenous-aquatic ratio, and (Pr + Ph)/(n-C17 + n-C18), reveal that redox conditions, the input of terrestrially derived organic matter, and the relative abundance of photoautotrophs were more variable in the shallower than in the deeper setting. This variability suggests that ecosystems in shallow restricted environments underwent more volatile changes than those in deeper settings. The shallower setting therefore records the effects of ubiquitous sea level fluctuations rather than an early onset of the environmental crisis preceding the extinction event, highlighting spatial heterogeneity in ecosystem responses and underscoring the importance of regional environmental context when interpreting extinction dynamics.
====
Free pdf:
Arctobatrachus urdensis gen. et sp. nov.
Rainer R. Schoch, Sanjukta Chakravorti, Florian Witzmann & Franz-Josef Lindemann (2026)
A giant plagiosaurid temnospondyl from Bjørnøya (Svalbard, Norway) and the origin of the plagiosaurid body plan
Papers in Palaeontology 12(4): e70115
doi: https://doi.org/10.1002/spp2.70115
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70115
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.70115
An articulated temnospondyl skeleton from Middle Triassic deposits of Bjørnøya (Bear Island) in the western Barents Sea is described as a new plagiosaurid genus and species, Arctobatrachus urdensis. With a body length well exceeding 2 m, it represents by far the largest known member of the Plagiosauridae. Large parts of the heavily weathered skull could be reconstructed on the basis of photos taken when the specimen was first discovered in 1948. The skull outline forms a near-perfect semicircle, with the jaw articulation located well behind the occipital condyles. The palatal and dentary tooth rows consist of large, closely set teeth and intercalated fangs, whereas the maxilla and coronoids bear numerous tiny teeth. The mandible is low but massive, with a prominent, posterodorsally curved retroarticular process. Plesiomorphic character states consist of a rhomboidal interclavicle, a tall and slender cleithrum, short disc-shaped vertebral centra, and the total absence of gastral scales and osteoderms. Some anterior vertebral centra closely resemble those of large capitosaurs and metoposaurs. A cladistic analysis finds A. urdensis to nest at the base of the plagiosaurids, sharing the extensive pectoral girdle and derived skull features with other taxa of that clade. With its huge size and enlarged gape, A. urdensis represents the first plagiosaurid top predator known so far, and its occurrence in marine deposits is consistent with the euryhaline habits of some other taxa in the clade.
Arctobatrachus urdensis gen. et sp. nov.
Rainer R. Schoch, Sanjukta Chakravorti, Florian Witzmann & Franz-Josef Lindemann (2026)
A giant plagiosaurid temnospondyl from Bjørnøya (Svalbard, Norway) and the origin of the plagiosaurid body plan
Papers in Palaeontology 12(4): e70115
doi: https://doi.org/10.1002/spp2.70115
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70115
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.70115
An articulated temnospondyl skeleton from Middle Triassic deposits of Bjørnøya (Bear Island) in the western Barents Sea is described as a new plagiosaurid genus and species, Arctobatrachus urdensis. With a body length well exceeding 2 m, it represents by far the largest known member of the Plagiosauridae. Large parts of the heavily weathered skull could be reconstructed on the basis of photos taken when the specimen was first discovered in 1948. The skull outline forms a near-perfect semicircle, with the jaw articulation located well behind the occipital condyles. The palatal and dentary tooth rows consist of large, closely set teeth and intercalated fangs, whereas the maxilla and coronoids bear numerous tiny teeth. The mandible is low but massive, with a prominent, posterodorsally curved retroarticular process. Plesiomorphic character states consist of a rhomboidal interclavicle, a tall and slender cleithrum, short disc-shaped vertebral centra, and the total absence of gastral scales and osteoderms. Some anterior vertebral centra closely resemble those of large capitosaurs and metoposaurs. A cladistic analysis finds A. urdensis to nest at the base of the plagiosaurids, sharing the extensive pectoral girdle and derived skull features with other taxa of that clade. With its huge size and enlarged gape, A. urdensis represents the first plagiosaurid top predator known so far, and its occurrence in marine deposits is consistent with the euryhaline habits of some other taxa in the clade.
======
======
Free pdf:
Zhongning Zhao, Chad Keates, J. Paul Grobler, Phillip. A. Bester, Stephanus Riekert & Neil Heideman (2026)
Climate, Continental Breakup and Habitat Shape Global Diversification and Biogeography of Turtles (Testudines)
Journal of Biogeography 53(7): e70314
doi: https://doi.org/10.1111/jbi.70314
https://onlinelibrary.wiley.com/doi/10.1111/jbi.70314
Evaluate the relative contributions of palaeotemperature, palaeogeographic reconfiguration, and habitat heterogeneity to the diversification and biogeographic history of turtles (Order Testudines) from the Triassic to the present.
Location and Time Period
Global; Triassic–Recent.
Taxa
Extant Testudines (time-calibrated phylogeny sampling ~286 species).
Methods
We combined a near-complete, time-calibrated phylogeny with complementary macroevolutionary and biogeographic methods. Diversification dynamics were explored using time- and temperature-dependent models (RPANDA), rate-shift analyses (BAMM), and state- and geography-dependent frameworks (GeoHiSSE). Historical ranges were inferred with multiple BioGeoBEARS models. Associations between reconstructed speciation rates and independent palaeotemperature records were tested using Pearson's correlation and detrended cross-correlation analysis (DCCA). Habitat categories (aquatic, amphibious, terrestrial) were coded for all taxa and explicitly incorporated into state-dependent models to assess their influence on diversification dynamics.
Results
Diversification dynamics of Testudines are consistent with interacting effects of palaeoclimate, plate tectonics and habitat. Testudines' diversification positively tracks palaeotemperature overall, but the sign and strength are clade-specific: some lineages speciate more in cooler intervals, others in warmer ones. Ancestral-range reconstructions identify multiple well-supported range shifts and vicariance events that are temporally concordant with major episodes of continental fragmentation. State-dependent analyses recover distinct diversification regimes among aquatic, amphibious and terrestrial lineages, indicating that habitat affinity modulates macroevolutionary responses to climatic and tectonic forcing.
Main Conclusions
No single factor alone explains turtle diversification through deep time. Instead, climatic transitions (both cooling and warming), tectonic reconfiguration of landmasses, and habitat-specific ecology and dispersal capacity were associated with the timing and geography of lineage accumulation in Testudines. Our results indicate that the refugial hypothesis is not universally supported across Testudines. Instead, support is lineage dependent, with some clades diversifying during cooler intervals and others during warmer periods. Moreover, the results indicate that habitat heterogeneity has played a key role in promoting speciation across the group.
====
====
Free pdf:
Ignacio J. Maniel, Rafael Almeida, David L. Kimbrough, G. Susana de la Puente, Alberto C. Garrido, Flavio Bellardini & J.Brian Mahoney (2026)
Albian zircon U-Pb crystallization ages from tuff beds in the Candeleros and Huincul formations, Neuquén Basin, Argentina
Gondwana Research (advance online publication)
doi: https://doi.org/10.1016/j.gr.2026.06.020
https://www.sciencedirect.com/science/article/pii/S1342937X26002005
Highlights
The dinosaur-rich Candeleros and Huincul Formations are early Albian in age rather than Cenomanian.
This adjustment in age impacts the genus richness patterns of fossils for the Cretaceous of South America and aligns it with the rest of the world.
The new age confirms the diachronous (northward-younging) development of fold-thrust belts along the compressive Andean margin.
Abstract
New U-Pb zircon laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) ages from airfall tuff beds in the dinosaur-rich nonmarine Candeleros Formation (111.4 ± 1.1 Ma) and overlying Huincul Formation (106.8 ± 2.2 Ma) in the Neuquén Basin of Argentina indicate Albian ages for both stratigraphic units. Three widely separated volcanogenic sandstones collected from basal Candeleros Formation strata ∼ 200 km north of the dated Candeleros airfall ash bed contain statistically indistinguishable clusters of young detrital zircon grains that confirm an early Albian (∼111 Ma) age for basal Candeleros strata across the entire Neuquén Basin. Depositionally synchronous zircon, as seen here in basal Candeleros strata, is a widespread and well-documented feature of retroarc basin assemblages adjacent to active volcanic arcs. The new Albian ages for the Candeleros and Huincul formations require a shift in the age of two of the six major tetrapod assemblages defined for the Neuquén Basin by ∼ 10–15 Myr and prompt a broad reevaluation of fossil assemblages and correlations across the Early-Late Cretaceous boundary, which are critical for the study of the evolution and diversification of Patagonian faunas. The early Albian Candeleros Formation is correlated here to the Cerro Barcino Formation of the dinosaur-bearing Chubut Group 500 km to the south of the Neuquén Basin. This correlation resolves formerly confounding biostratigraphic correlation between these two areas. The new ages also place constraints on the timing of Andean fold and thrust belt inception and further indicate that pedogenic contrasts between the Candeleros and Huincul formations reflect the emergence of global climate from cooler conditions toward warmer Greenhouse World conditions broadly characteristic of the mid-Cretaceous.
===
Free pdf:
Stella Z. Buchwald, Daniel Birgel, Evelyn Kustatscher, Herwig Prinoth, Francesca Galasso, Baran Karapunar, Anja B. Frank, Mónica Alejandra Gómez Correa, Niko Lahajnar, Jörn Peckmann & William J. Foster (2026)
Molecular fossils record shallow marine ecosystem changes prior to and across the Permian−Triassic mass extinction in the Dolomites (Italy)
GSA Bulletin (2026)
DOI: https://doi.org/10.1130/B39055.1
https://pubs.geoscienceworld.org/gsa/gsabulletin/article/doi/10.1130/B39055.1/734243/Molecular-fossils-record-shallow-marine-ecosystem
The Permian−Triassic mass extinction, the most severe biotic crisis of the Phanerozoic, has been linked to environmental perturbations triggered by the eruptions of the Siberian Traps Large Igneous Province. However, several of these perturbations have previously been demonstrated to have started several hundred thousand of years before the main extinction phase. To explore this timing and its ecological implications, we analyzed molecular fossils across the Permian−Triassic transition in two shallow marine carbonate ramp sections in the tropical Tethys Ocean of the Dolomites (northern Italy). Both the shallower (Siusi/Seis) and the deeper (Seres) settings record a sudden increase in polycyclic aromatic hydrocarbons, including pyrene and coronene, just above the extinction interval. These compounds probably originated from the combustion of organic-rich sedimentary rocks during Siberian Traps sill emplacement and were subsequently distributed across the study area. Redox-sensitive and source-indicative molecular fossil indices, such as pristane/phytane (Pr/Ph), the terrigenous-aquatic ratio, and (Pr + Ph)/(n-C17 + n-C18), reveal that redox conditions, the input of terrestrially derived organic matter, and the relative abundance of photoautotrophs were more variable in the shallower than in the deeper setting. This variability suggests that ecosystems in shallow restricted environments underwent more volatile changes than those in deeper settings. The shallower setting therefore records the effects of ubiquitous sea level fluctuations rather than an early onset of the environmental crisis preceding the extinction event, highlighting spatial heterogeneity in ecosystem responses and underscoring the importance of regional environmental context when interpreting extinction dynamics.
====
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