Basal alligatoroid braincase from Late Cretaceous of Uzbekistan + choristodere middle ear + Maastrichtian Antarctica plesiosaur fall community + Protorothyris skull + more
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Ben Creisler
Dec 23, 2025, 1:45:44 PM12/23/25
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Ben Creisler
I.T. Kuzmin, P.P. Skutschas and H.-D. Sues (2025)
Braincase of the earliest known alligatoroid (Crocodylomorpha: Crocodylia) from the Upper Cretaceous of Uzbekistan
Proceedings of the Zoological Institute RAS 329(4): 502–517
doi: https://doi.org/10.31610/trudyzin/2025.329.4.502
https://www.zin.ru/journals/trudyzin/eng/publication.html?id=618
Free pdf:
https://www.zin.ru/journals/trudyzin/doc/vol_329_4/TZ_329_4_Kuzmin2.pdf
The early evolutionary history of the crown-group Crocodylia remains obscured by a sparse fossil record from the early Late Cretaceous. We describe a well-preserved crocodylian braincase (ZIN PH 92/204) from the Upper Cretaceous (Turonian) Bissekty Formation in Uzbekistan, using computed microtomography and 3D modelling. Two independent phylogenetic analyses consistently recovered this specimen as a basal alligatoroid, closely related to the Paleocene-Miocene European genus Diplocynodon. This find provides the first firm evidence of a Diplocynodon-like basal alligatoroid in the Late Cretaceous of Central Asia. ZIN PH 92/204 represents the stratigraphically oldest alligatoroid reported to date, filling a critical temporal gap and resolving the previously revealed incongruence where the stratigraphically younger Diplocynodon appeared more basal than the older but more derived alligatoroids. ZIN PH 92/204 potentially represents one of the earliest crown-group crocodylians occurring in the Turonian, and, combined with other putative early forms (Portugalosuchus, Zholsuchus), indicates that the primary lineages of Crocodylia (Alligatoroidea and Longirostres) had already diverged by the beginning of the Late Cretaceous. This suggests a much earlier origin for Crocodylia, potentially dating back to the Early Cretaceous.
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I.T. Kuzmin and D.D. Vitenko (2025)
Middle ear anatomy and position of stapes in choristoderes (Reptilia: Neodiapsida)
Proceedings of the Zoological Institute RAS 329(4): 489–501 ·
doi: https://doi.org/10.31610/trudyzin/2025.329.4.489
https://www.zin.ru/journals/trudyzin/eng/publication.html?id=617
Free pdf:
https://www.zin.ru/journals/trudyzin/doc/vol_329_4/TZ_329_4_Kuzmin1.pdf
In this article, we review several aspects of the choristoderan cranial anatomy related to their middle ear structure. Choristoderes had an air-filled middle ear (pharyngotympanic) cavity bordered by the osseous postquadrate fossa on the posterolateral surface of their cranium. The presence of a tympanic membrane in choristoderes remains ambiguous; if present, it was supported by the squamosal and quadratojugal rather than the quadrate – a configuration that distinguishes choristoderes from most crown-group reptiles. The stapes of choristoderes is still unknown but was likely positioned posteromedial to the quadrate, was mobile and specialized for sound conduction, as in crown-group reptiles, rather than serving for skull consolidation and supporting the quadrate against the braincase, as in stem reptiles and basal neodiapsids. Hearing in choristoderes was likely adapted to low-frequency sounds (approximately 100–1000 Hz), enabling sensitivity to both water-borne and air-borne vibrations – a capability consistent with the semi-aquatic lifestyle inferred for most members of this clade.
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Marianella Talevi, Soledad Brezina & Darío G. Lazo (2025)
Successional Stages of a Maastrichtian Plesiosaur Fall Community from Antarctica
Cretaceous Research 106306
doi: https://doi.org/10.1016/j.cretres.2025.106306
https://www.sciencedirect.com/science/article/abs/pii/S0195667125002290
Highlights
Ecological successions in fossil bones of Mesozoic marine reptiles.
Four ecological succession stages identified in Maastrichtian plesiosaur bones.
Sclerobionts and borings show prolonged exposure and complex colonization phases.
Framboid pyrite reveals anaerobic bacterial activity during the sulfophilic stage.
Study clarifies ancient marine carcass communities and paleoecosystem dynamics
Abstract
Research on ecological successions in recent skeletal remains, such as those of whales, has revealed specific colonization patterns and four distinct succession phases. These succession patterns can also be inferred in the fossil record from evidence such as bioerosion traces, bone encrustation, and associated body fossils. The study of ecological successions in fossil bones of Mesozoic marine reptiles not only helps to understand the phases of degradation and entombing in the past but also contributes to our knowledge of the communities associated with these carcasses during that time. In this work, the presence of sclerobionts (represented by micro and macroborings) in bone remains of a plesiosaur from the upper Maastrichtian of Antarctica was identified and described, interpreting the phases of ecological succession in a high-latitude marine environment. Macroborings were assigned to Trypanites and Osedacoides. The microborings, similar to Wedl tunnels, were attributed to cyanobacteria and fungi, indicating that the bones were exposed for a long time. Furthermore, framboid pyrite in the bones shows anaerobic stages associated with bacterial activity. The four known stages of ecological succession were documented: the mobile scavenger stage, identified by bite marks; the opportunistic enrichment stage by Osedacoides; the sulfophilic stage, marked by modified vascular channels filled with pyrite; and the reef stage, by Trypanites traces, which indicate colonization by organisms before final burial. These findings enhance our understanding of the interactions between microorganisms and mineralization in ancient marine vertebrates, and aid in reconstructing paleocommunities associated with marine reptile falls, offering valuable insights into past ecosystem dynamics.
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Some mainly reptilian papers:
Free pdf:
I.T. Kuzmin, P.P. Skutschas and H.-D. Sues (2025)
Braincase of the earliest known alligatoroid (Crocodylomorpha: Crocodylia) from the Upper Cretaceous of Uzbekistan
Proceedings of the Zoological Institute RAS 329(4): 502–517
doi: https://doi.org/10.31610/trudyzin/2025.329.4.502
https://www.zin.ru/journals/trudyzin/eng/publication.html?id=618
Free pdf:
https://www.zin.ru/journals/trudyzin/doc/vol_329_4/TZ_329_4_Kuzmin2.pdf
The early evolutionary history of the crown-group Crocodylia remains obscured by a sparse fossil record from the early Late Cretaceous. We describe a well-preserved crocodylian braincase (ZIN PH 92/204) from the Upper Cretaceous (Turonian) Bissekty Formation in Uzbekistan, using computed microtomography and 3D modelling. Two independent phylogenetic analyses consistently recovered this specimen as a basal alligatoroid, closely related to the Paleocene-Miocene European genus Diplocynodon. This find provides the first firm evidence of a Diplocynodon-like basal alligatoroid in the Late Cretaceous of Central Asia. ZIN PH 92/204 represents the stratigraphically oldest alligatoroid reported to date, filling a critical temporal gap and resolving the previously revealed incongruence where the stratigraphically younger Diplocynodon appeared more basal than the older but more derived alligatoroids. ZIN PH 92/204 potentially represents one of the earliest crown-group crocodylians occurring in the Turonian, and, combined with other putative early forms (Portugalosuchus, Zholsuchus), indicates that the primary lineages of Crocodylia (Alligatoroidea and Longirostres) had already diverged by the beginning of the Late Cretaceous. This suggests a much earlier origin for Crocodylia, potentially dating back to the Early Cretaceous.
=====
Free pdf:
I.T. Kuzmin and D.D. Vitenko (2025)
Middle ear anatomy and position of stapes in choristoderes (Reptilia: Neodiapsida)
Proceedings of the Zoological Institute RAS 329(4): 489–501 ·
doi: https://doi.org/10.31610/trudyzin/2025.329.4.489
https://www.zin.ru/journals/trudyzin/eng/publication.html?id=617
Free pdf:
https://www.zin.ru/journals/trudyzin/doc/vol_329_4/TZ_329_4_Kuzmin1.pdf
In this article, we review several aspects of the choristoderan cranial anatomy related to their middle ear structure. Choristoderes had an air-filled middle ear (pharyngotympanic) cavity bordered by the osseous postquadrate fossa on the posterolateral surface of their cranium. The presence of a tympanic membrane in choristoderes remains ambiguous; if present, it was supported by the squamosal and quadratojugal rather than the quadrate – a configuration that distinguishes choristoderes from most crown-group reptiles. The stapes of choristoderes is still unknown but was likely positioned posteromedial to the quadrate, was mobile and specialized for sound conduction, as in crown-group reptiles, rather than serving for skull consolidation and supporting the quadrate against the braincase, as in stem reptiles and basal neodiapsids. Hearing in choristoderes was likely adapted to low-frequency sounds (approximately 100–1000 Hz), enabling sensitivity to both water-borne and air-borne vibrations – a capability consistent with the semi-aquatic lifestyle inferred for most members of this clade.
=====
Free pdf:
Joaquin Pedro Bogado, André Eduardo Piacentini Pinheiro & Pedro S. R. Romano
A reassessment of the species “Podocnemis” brasiliensis (Pleurodira, Pelomedusoides) from the Late Cretaceous Bauru Group
Swiss Journal of Palaeontology 144: 77
doi: https://doi.org/10.1186/s13358-025-00418-w
https://link.springer.com/article/10.1186/s13358-025-00418-w
The Bauru Group of the Paraná Basin (Upper Cretaceous) has yielded a rich assemblage of fossil turtles, with nine formally named species. However, many of the taxa described for this unit are poorly known, being considered nomina dubia by most authors. One such taxon is “Podocnemis” brasiliensis, described in the 1930’s and known only from its lectotype, a fragmentary plastron. In this paper we present new turtle remains that are attributable to “P.” brasiliensis, preserving parts of the plastron that were lacking in the lectotype. This novel anatomical information has permitted us to emend the diagnosis of “P.” brasiliensis and recognize it as a valid species of Pan-Podocnemididae, although its phylogenetic position within that clade is still unsettled. Fragmentary specimens that had been attributed to “P.” brasiliensis in the past were revised, and we concluded they cannot be confidently assigned to this taxon. We also analyzed variation in average shell thickness among podocnemidoids, to evaluate whether this variation was correlated with taxonomic distinctions. Though we could not estimate the average shell thickness for “P.” brasiliensis, our results demonstrate that the species Bauruemys elegans has a relatively thinner shell in comparison to other South American podocnemidoids.
Joaquin Pedro Bogado, André Eduardo Piacentini Pinheiro & Pedro S. R. Romano
A reassessment of the species “Podocnemis” brasiliensis (Pleurodira, Pelomedusoides) from the Late Cretaceous Bauru Group
Swiss Journal of Palaeontology 144: 77
doi: https://doi.org/10.1186/s13358-025-00418-w
https://link.springer.com/article/10.1186/s13358-025-00418-w
The Bauru Group of the Paraná Basin (Upper Cretaceous) has yielded a rich assemblage of fossil turtles, with nine formally named species. However, many of the taxa described for this unit are poorly known, being considered nomina dubia by most authors. One such taxon is “Podocnemis” brasiliensis, described in the 1930’s and known only from its lectotype, a fragmentary plastron. In this paper we present new turtle remains that are attributable to “P.” brasiliensis, preserving parts of the plastron that were lacking in the lectotype. This novel anatomical information has permitted us to emend the diagnosis of “P.” brasiliensis and recognize it as a valid species of Pan-Podocnemididae, although its phylogenetic position within that clade is still unsettled. Fragmentary specimens that had been attributed to “P.” brasiliensis in the past were revised, and we concluded they cannot be confidently assigned to this taxon. We also analyzed variation in average shell thickness among podocnemidoids, to evaluate whether this variation was correlated with taxonomic distinctions. Though we could not estimate the average shell thickness for “P.” brasiliensis, our results demonstrate that the species Bauruemys elegans has a relatively thinner shell in comparison to other South American podocnemidoids.
====
Marianella Talevi, Soledad Brezina & Darío G. Lazo (2025)
Successional Stages of a Maastrichtian Plesiosaur Fall Community from Antarctica
Cretaceous Research 106306
doi: https://doi.org/10.1016/j.cretres.2025.106306
https://www.sciencedirect.com/science/article/abs/pii/S0195667125002290
Highlights
Ecological successions in fossil bones of Mesozoic marine reptiles.
Four ecological succession stages identified in Maastrichtian plesiosaur bones.
Sclerobionts and borings show prolonged exposure and complex colonization phases.
Framboid pyrite reveals anaerobic bacterial activity during the sulfophilic stage.
Study clarifies ancient marine carcass communities and paleoecosystem dynamics
Abstract
Research on ecological successions in recent skeletal remains, such as those of whales, has revealed specific colonization patterns and four distinct succession phases. These succession patterns can also be inferred in the fossil record from evidence such as bioerosion traces, bone encrustation, and associated body fossils. The study of ecological successions in fossil bones of Mesozoic marine reptiles not only helps to understand the phases of degradation and entombing in the past but also contributes to our knowledge of the communities associated with these carcasses during that time. In this work, the presence of sclerobionts (represented by micro and macroborings) in bone remains of a plesiosaur from the upper Maastrichtian of Antarctica was identified and described, interpreting the phases of ecological succession in a high-latitude marine environment. Macroborings were assigned to Trypanites and Osedacoides. The microborings, similar to Wedl tunnels, were attributed to cyanobacteria and fungi, indicating that the bones were exposed for a long time. Furthermore, framboid pyrite in the bones shows anaerobic stages associated with bacterial activity. The four known stages of ecological succession were documented: the mobile scavenger stage, identified by bite marks; the opportunistic enrichment stage by Osedacoides; the sulfophilic stage, marked by modified vascular channels filled with pyrite; and the reef stage, by Trypanites traces, which indicate colonization by organisms before final burial. These findings enhance our understanding of the interactions between microorganisms and mineralization in ancient marine vertebrates, and aid in reconstructing paleocommunities associated with marine reptile falls, offering valuable insights into past ecosystem dynamics.
====
Kelsey M. Jenkins, Adam D. B. Behlke & Hans-Dieter Sues (2025)
New anatomical details concerning the cranial structure of the early Permian stem reptile Protorothyris archeri revealed by μCT, with implications for the evolution of olfaction in reptiles
Palaeontology 68(6): e70038
doi: https://doi.org/10.1111/pala.70038
https://onlinelibrary.wiley.com/doi/10.1111/pala.70038
Re-examination of early-diverging stem reptiles can provide valuable phylogenetic data and insights into the evolution of sensory systems during the terrestrialization of tetrapods in the late Palaeozoic. Here, we apply μCT imaging to a previously undescribed specimen of Protorothyris archeri. Our segmentations revealed previously unknown anatomical details of this species, including enlarged dentary teeth, denticles on the parabasisphenoid, and the morphology of the internal surfaces of the dermatocranial elements. We included this specimen within a phylogenetic matrix of 177 operational taxonomic units and 628 morphological characters designed to examine the relationships of early-diverging amniotes, particularly stem reptiles. Bayesian and parsimony analyses reveal that there is still topological discordance among some clades (e.g. caseasaurs, varanopids), although these analyses confirm that ‘protorothyridids’ do not form a clade, consistent with other recent phylogenetic analyses. The position of P. archeri as an early-diverging stem reptile in our analyses suggests that it may provide insight into the evolution of the olfactory system as the reptile lineage diversified throughout the Permian, based on the morphology of the cristae cranii. However, more anatomical work is needed to determine if the depth of the cristae cranii is indicative of olfactory bulb size and capability.
New anatomical details concerning the cranial structure of the early Permian stem reptile Protorothyris archeri revealed by μCT, with implications for the evolution of olfaction in reptiles
Palaeontology 68(6): e70038
doi: https://doi.org/10.1111/pala.70038
https://onlinelibrary.wiley.com/doi/10.1111/pala.70038
Re-examination of early-diverging stem reptiles can provide valuable phylogenetic data and insights into the evolution of sensory systems during the terrestrialization of tetrapods in the late Palaeozoic. Here, we apply μCT imaging to a previously undescribed specimen of Protorothyris archeri. Our segmentations revealed previously unknown anatomical details of this species, including enlarged dentary teeth, denticles on the parabasisphenoid, and the morphology of the internal surfaces of the dermatocranial elements. We included this specimen within a phylogenetic matrix of 177 operational taxonomic units and 628 morphological characters designed to examine the relationships of early-diverging amniotes, particularly stem reptiles. Bayesian and parsimony analyses reveal that there is still topological discordance among some clades (e.g. caseasaurs, varanopids), although these analyses confirm that ‘protorothyridids’ do not form a clade, consistent with other recent phylogenetic analyses. The position of P. archeri as an early-diverging stem reptile in our analyses suggests that it may provide insight into the evolution of the olfactory system as the reptile lineage diversified throughout the Permian, based on the morphology of the cristae cranii. However, more anatomical work is needed to determine if the depth of the cristae cranii is indicative of olfactory bulb size and capability.
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