Juvenile ornithopod femur from Cretaceous of Argentina + earliest glyptosaurids from Europe + Kryptobaatar digital cranial endocast + Leptictis brain anatomy (free pdfs)
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Ben Creisler
Sep 3, 2026, 7:05:02 PMSep 3
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Ben Creisler
Georgios L. Georgalis and Bastien Mennecart (2026)
Earliest occurrence of glyptosaurid lizards from Europe
Acta Palaeontologica Polonica 71(3): 509-518
doi:10.4202/app.01331.2026
https://www.app.pan.pl/article/item/app013312026.html
Glyptosauridae represents a bizarre group of lizards that are heavily armored, covered across their body with distinctive osteoderms. Glyptosaurids are iconic members of Eocene herpetofaunas from the Northern Hemisphere, including Europe, where they eventually became extinct in the latter continent at the “Grande Coupure” extinction event at the Eocene/Oligocene boundary. As their oldest European fossils have so far been documented in the earliest Eocene, it has been commonly accepted that glyptosaurids dispersed to that continent from North America (where they are already known from Late Cretaceous and Paleocene localities), somewhen after the Paleocene–Eocene Thermal Maximum (PETM) at around 56 Ma, following a similar dispersal pattern of several other terrestrial vertebrates. We here describe an isolated osteoderm from the upper Paleocene (MP 6) of Cernay in the Paris Basin, France, which can be identified with certainty as a glyptosaurid. A detailed overview of all glyptosaurid occurrences from Europe is also provided. Even if scarce and limited, the new material from Cernay provides definite evidence that glyptosaurids arrived in Europe earlier than previously thought, apparently being one of the so called “precursor” dispersers that managed to arrive in Europe before the PETM.
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Free pdf:
Thomas E. Macrini & Timothy Rowe (2026)
New quantitative data from a digital cranial endocast of Kryptobaatar dashzevegi (Multituberculata, Mammalia) and a new estimate of body mass
Frontiers in Mammal Science 5:1913320
doi: https://doi.org/10.3389/fmamm.2026.1913320
https://www.frontiersin.org/journals/mammal-science/articles/10.3389/fmamm.2026.1913320/full
We extracted a digital cranial endocast from a high-resolution X-ray computed tomography scan of a specimen of the Late Cretaceous Mongolian multituberculate Kryptobaatar dashzevegi. The digital endocast shows qualitative and quantitative differences from a previously published description of a natural endocast of K. dashzevegi. In particular, the endocranial volume (EV) of the digital endocast, measured from high-resolution X-ray computed tomography (CT) scans of a skull, is considerably smaller than a previous estimate of EV for Kryptobaatar from the natural endocast determined using the equation for the partial volume of a cylinder. The new, more accurate measure of EV for Kryptobaatar (EV = 0.34 mL), along with a new estimate of body mass, has implications for calculating the encephalization quotient (EQ) for this taxon and making comparisons with relative brain size in mammals in general. In particular, the EQ of Kryptobaatar was calculated as 0.32, which is significantly lower than other reported EQs for multituberculates, multiple basal mammals, and the stem mammal Hadrocodium wui.
Carl C. Van Gent, John R. Wible, Stephen L. Brusatte, Lawiza Kamran, and Ornella C. Bertrand (2026)
Revisiting the brain anatomy of the early Oligocene eutherian mammal Leptictis based on virtual endocasts
Acta Palaeontologica Polonica 71(3): 519-534
doi:10.4202/app.01343.2026
https://www.app.pan.pl/article/item/app013432026.html
Leptictidae are an extinct early Cenozoic group of mammals that has been challenging to place phylogenetically within Eutheria. They have been considered closely related to various crown placental groups such as Lipotyphla, Macroscelidea, or Euarchontoglires based on their “insectivore-grade” features, or as very early placentals or even non-placental eutherians because of their plesiomorphies. Since the 1920s their brain anatomy has been studied using natural endocasts, and oftentimes they are viewed as a model for the ancestral neurosensory conditions of placentals. Here, we use computed tomography (CT) for the first time to generate digital endocranial casts of two species of the canonical early Oligocene leptictid genus, Leptictis. Both species present similar endocranial anatomies with variation in the number of condyloid canals and the enclosure of the inferior petrosal sinus. Critically, we find differences compared to descriptions of natural endocasts, most notably that the rhinal fissure is more dorsally positioned, suggesting that Leptictis did not have a particularly expanded neocortex compared to Lipotyphla, Afrosoricida, and Macroscelidea. Furthermore, Leptictis was not particularly encephalized, and its brain size relative to body size was within the range of modern insectivorous taxa and Eocene mammals generally. Similar endocranial features in Leptictis and Eoryctes are likely plesiomorphic and do not represent a close phylogenetic relationship, and brain anatomy does not clarify the troublesome relationships of leptictids. The small neocortex and petrosal lobules might reflect fossorial adaptations in Leptictis, but more endocranial data from other Leptictidae will be fundamental to better understand any neurosensory shift that may have occurred within this group.
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Some recent papers:
Not yet mentioned dino paper:
Free pdf:
Airam Rodríguez-Borges, Javier González-Dionis, Leonardo S. Filippi, Ignacio A. Cerda, Yuong-Nam Lee & Penélope Cruzado-Caballero (2026)
Ontogenetic variation in an ornithopod femur from the Upper Cretaceous of Argentina.
Geologica Acta 24.17: 1-17
DOI: https://doi.org/10.1344/GeologicaActa2026.24.17
https://revistes.ub.edu/index.php/GEOACTA/article/view/54338
The paleobiodiversity of Gondwanan ornithopods and the number of indeterminate remains attributed to this clade have increased markedly in recent decades, especially in South America. The femur is one of the most frequently preserved postcranial elements in the South American fossil record and often retains diagnostic features that have been used to establish new species. However, the effect of ontogenetic and intraspecific variation on femoral morphology remains poorly understood in South American ornithopods.
Here we describe and analyze a small right femur (MAU-PV-CO-684) from the Bajo de la Carpa Formation (Santonian), recovered from the Cerro Overo–La Invernada area (Rincón de los Sauces, Neuquén, Argentina). Histological analyses indicate that the specimen is an early juvenile, probably less than one year old at the time of death. Despite its immature ontogenetic stage, the femur retains several features consistent with the Ornithopoda, including an anteroposteriorly curved diaphysis and a femoral neck that separates the femoral head from the greater trochanter.
A preliminary phylogenetic analysis places MAU-PV-CO-684 within Rhabdodontomorpha, with alternative placements among early-diverging iguanodonts or early-diverging Neornithischians. However, several femoral characters with strong phylogenetic signal also exhibit ontogenetic variability, suggesting that developmental stage can influence phylogenetic inference when analyzing isolated elements. Therefore, its taxonomic assignment has been preferred as Iguanodontia indet. MAU-PV-CO-684 provides new insights into the ontogenetic variation of ornithopod femora in Gondwana, highlights the need to integrate histological data when evaluating fragmentary material, and underscores the taxonomic importance of femoral characters in South American ornithopods.
Airam Rodríguez-Borges, Javier González-Dionis, Leonardo S. Filippi, Ignacio A. Cerda, Yuong-Nam Lee & Penélope Cruzado-Caballero (2026)
Ontogenetic variation in an ornithopod femur from the Upper Cretaceous of Argentina.
Geologica Acta 24.17: 1-17
DOI: https://doi.org/10.1344/GeologicaActa2026.24.17
https://revistes.ub.edu/index.php/GEOACTA/article/view/54338
The paleobiodiversity of Gondwanan ornithopods and the number of indeterminate remains attributed to this clade have increased markedly in recent decades, especially in South America. The femur is one of the most frequently preserved postcranial elements in the South American fossil record and often retains diagnostic features that have been used to establish new species. However, the effect of ontogenetic and intraspecific variation on femoral morphology remains poorly understood in South American ornithopods.
Here we describe and analyze a small right femur (MAU-PV-CO-684) from the Bajo de la Carpa Formation (Santonian), recovered from the Cerro Overo–La Invernada area (Rincón de los Sauces, Neuquén, Argentina). Histological analyses indicate that the specimen is an early juvenile, probably less than one year old at the time of death. Despite its immature ontogenetic stage, the femur retains several features consistent with the Ornithopoda, including an anteroposteriorly curved diaphysis and a femoral neck that separates the femoral head from the greater trochanter.
A preliminary phylogenetic analysis places MAU-PV-CO-684 within Rhabdodontomorpha, with alternative placements among early-diverging iguanodonts or early-diverging Neornithischians. However, several femoral characters with strong phylogenetic signal also exhibit ontogenetic variability, suggesting that developmental stage can influence phylogenetic inference when analyzing isolated elements. Therefore, its taxonomic assignment has been preferred as Iguanodontia indet. MAU-PV-CO-684 provides new insights into the ontogenetic variation of ornithopod femora in Gondwana, highlights the need to integrate histological data when evaluating fragmentary material, and underscores the taxonomic importance of femoral characters in South American ornithopods.
====
====
Free pdf:
Georgios L. Georgalis and Bastien Mennecart (2026)
Earliest occurrence of glyptosaurid lizards from Europe
Acta Palaeontologica Polonica 71(3): 509-518
doi:10.4202/app.01331.2026
https://www.app.pan.pl/article/item/app013312026.html
Glyptosauridae represents a bizarre group of lizards that are heavily armored, covered across their body with distinctive osteoderms. Glyptosaurids are iconic members of Eocene herpetofaunas from the Northern Hemisphere, including Europe, where they eventually became extinct in the latter continent at the “Grande Coupure” extinction event at the Eocene/Oligocene boundary. As their oldest European fossils have so far been documented in the earliest Eocene, it has been commonly accepted that glyptosaurids dispersed to that continent from North America (where they are already known from Late Cretaceous and Paleocene localities), somewhen after the Paleocene–Eocene Thermal Maximum (PETM) at around 56 Ma, following a similar dispersal pattern of several other terrestrial vertebrates. We here describe an isolated osteoderm from the upper Paleocene (MP 6) of Cernay in the Paris Basin, France, which can be identified with certainty as a glyptosaurid. A detailed overview of all glyptosaurid occurrences from Europe is also provided. Even if scarce and limited, the new material from Cernay provides definite evidence that glyptosaurids arrived in Europe earlier than previously thought, apparently being one of the so called “precursor” dispersers that managed to arrive in Europe before the PETM.
=====
=====
Free pdf:
Thomas E. Macrini & Timothy Rowe (2026)
New quantitative data from a digital cranial endocast of Kryptobaatar dashzevegi (Multituberculata, Mammalia) and a new estimate of body mass
Frontiers in Mammal Science 5:1913320
doi: https://doi.org/10.3389/fmamm.2026.1913320
https://www.frontiersin.org/journals/mammal-science/articles/10.3389/fmamm.2026.1913320/full
We extracted a digital cranial endocast from a high-resolution X-ray computed tomography scan of a specimen of the Late Cretaceous Mongolian multituberculate Kryptobaatar dashzevegi. The digital endocast shows qualitative and quantitative differences from a previously published description of a natural endocast of K. dashzevegi. In particular, the endocranial volume (EV) of the digital endocast, measured from high-resolution X-ray computed tomography (CT) scans of a skull, is considerably smaller than a previous estimate of EV for Kryptobaatar from the natural endocast determined using the equation for the partial volume of a cylinder. The new, more accurate measure of EV for Kryptobaatar (EV = 0.34 mL), along with a new estimate of body mass, has implications for calculating the encephalization quotient (EQ) for this taxon and making comparisons with relative brain size in mammals in general. In particular, the EQ of Kryptobaatar was calculated as 0.32, which is significantly lower than other reported EQs for multituberculates, multiple basal mammals, and the stem mammal Hadrocodium wui.
====
Free pdf:
Carl C. Van Gent, John R. Wible, Stephen L. Brusatte, Lawiza Kamran, and Ornella C. Bertrand (2026)
Revisiting the brain anatomy of the early Oligocene eutherian mammal Leptictis based on virtual endocasts
Acta Palaeontologica Polonica 71(3): 519-534
doi:10.4202/app.01343.2026
https://www.app.pan.pl/article/item/app013432026.html
Leptictidae are an extinct early Cenozoic group of mammals that has been challenging to place phylogenetically within Eutheria. They have been considered closely related to various crown placental groups such as Lipotyphla, Macroscelidea, or Euarchontoglires based on their “insectivore-grade” features, or as very early placentals or even non-placental eutherians because of their plesiomorphies. Since the 1920s their brain anatomy has been studied using natural endocasts, and oftentimes they are viewed as a model for the ancestral neurosensory conditions of placentals. Here, we use computed tomography (CT) for the first time to generate digital endocranial casts of two species of the canonical early Oligocene leptictid genus, Leptictis. Both species present similar endocranial anatomies with variation in the number of condyloid canals and the enclosure of the inferior petrosal sinus. Critically, we find differences compared to descriptions of natural endocasts, most notably that the rhinal fissure is more dorsally positioned, suggesting that Leptictis did not have a particularly expanded neocortex compared to Lipotyphla, Afrosoricida, and Macroscelidea. Furthermore, Leptictis was not particularly encephalized, and its brain size relative to body size was within the range of modern insectivorous taxa and Eocene mammals generally. Similar endocranial features in Leptictis and Eoryctes are likely plesiomorphic and do not represent a close phylogenetic relationship, and brain anatomy does not clarify the troublesome relationships of leptictids. The small neocortex and petrosal lobules might reflect fossorial adaptations in Leptictis, but more endocranial data from other Leptictidae will be fundamental to better understand any neurosensory shift that may have occurred within this group.
===
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