Acinacodus and other Mesozoic mammal molar-like teeth replacement + crocodile skeletal pathologies and archosaur paleopathologies
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Ben Creisler
Nov 15, 2025, 7:25:22 PMNov 15
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Ben Creisler
Alexis Cornille, Kyla Beguesse, Ewan Wolff, Clemens Zinner, Patrick Asbach, François Clarac & Florian Witzmann (2025)
Skeletal pathologies in extant crocodilians as a window into the paleopathology of fossil archosaurs
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.70079
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.70079
Free pdf:
https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.70079
Crocodilians, together with birds, are the only extant relatives to many extinct archosaur groups, making them highly important for interpreting paleopathological conditions in a phylogenetic disease bracketing model. Despite this, comprehensive data on osteopathologies in crocodilians remain scarce. Here, we present the largest osteopathological survey to date of extant crocodilian skeletal material, comprising 927 individuals and 22,281 skeletal elements spanning all three extant crocodilian families. Our results reveal 1969 osteopathologies from 414 of all individuals (44.7%). Bone trauma is the most prevalent osteopathology, representing 43.9% of all pathologies observed, followed by inflammatory lesions (27.3%) and degenerative joint disorders (11.5%). Statistical analyses demonstrate significant correlations between adult body size, ontogeny, and trauma frequency, with large-sized crocodilian species and older individuals sustaining substantially more injuries. The skull, particularly the dorsal cranial aspect, showed considerably higher involvement of trauma compared to the rest of the skeleton. We also show that non-traumatic pathologies such as inflammation and degenerative joint disorders increase in larger crocodilian species and with ontogeny. These findings underscore the behavioral and physiological drivers of skeletal disease in modern crocodilians and offer key comparative data for interpreting osteopathologies in fossil archosaurs and archosauriforms.
New papers:
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Alexander O. Averianov, Alexey V. Lopatin, Dmitry A. Slobodin, Pavel P. Skutschas & Olga N. Vladimirova (2025)
Replacement of molariform teeth in amphidontid eutriconodontan Acinacodus and other Mesozoic mammals
Palaeobiodiversity and Palaeoenvironments (advance online publication)
doi: https://doi.org/10.1007/s12549-025-00678-x
https://link.springer.com/article/10.1007/s12549-025-00678-x
The replacement of molariform teeth has been documented for the Early Cretaceous gobiconodontid eutriconodontans (Gobiconodon, Repenomamus, and Spinolestes). It was also assumed for the amphidontid eutriconodontan Acinacodus from the Early Cretaceous of Western Siberia, Russia, based on differential wear of lower molars. Here we report on a new specimen of Acinacodus, which preserves a partially mineralised replacing tooth in the first molariform locus. This specimen also shows slit-like pits along the alveolar border lingual to m1-3, which are interpreted as the dental lamina pits (openings for gubernacular canals). The replacement of lower molariforms in Acinacodus occurred in one wave, which affected anterior molariforms (m1-3). The posterior molariforms (m4-5) and premolars (p1-2) possibly were not replaced. The p1, or dp1, was shed early in life and its alveolus was plugged by bone. In contrast to currently adopted view, the replacement of molariform teeth was widely distributed in stem mammals and can be documented for Morganucodon, Megazostrodon, and Dinnetherium. The prolonged functioning of the dental lamina in Morganucodon and tegotheriid docodontans is likely related with a late eruption of the last lower molariform tooth. From the jaw structures associated with the dental lamina in non-mammalian cynodonts (groove and pits), the dental lamina groove is retained at least in some Gobiconodontidae and the dental lamina pits are retained in Amphidontidae.
Alexander O. Averianov, Alexey V. Lopatin, Dmitry A. Slobodin, Pavel P. Skutschas & Olga N. Vladimirova (2025)
Replacement of molariform teeth in amphidontid eutriconodontan Acinacodus and other Mesozoic mammals
Palaeobiodiversity and Palaeoenvironments (advance online publication)
doi: https://doi.org/10.1007/s12549-025-00678-x
https://link.springer.com/article/10.1007/s12549-025-00678-x
The replacement of molariform teeth has been documented for the Early Cretaceous gobiconodontid eutriconodontans (Gobiconodon, Repenomamus, and Spinolestes). It was also assumed for the amphidontid eutriconodontan Acinacodus from the Early Cretaceous of Western Siberia, Russia, based on differential wear of lower molars. Here we report on a new specimen of Acinacodus, which preserves a partially mineralised replacing tooth in the first molariform locus. This specimen also shows slit-like pits along the alveolar border lingual to m1-3, which are interpreted as the dental lamina pits (openings for gubernacular canals). The replacement of lower molariforms in Acinacodus occurred in one wave, which affected anterior molariforms (m1-3). The posterior molariforms (m4-5) and premolars (p1-2) possibly were not replaced. The p1, or dp1, was shed early in life and its alveolus was plugged by bone. In contrast to currently adopted view, the replacement of molariform teeth was widely distributed in stem mammals and can be documented for Morganucodon, Megazostrodon, and Dinnetherium. The prolonged functioning of the dental lamina in Morganucodon and tegotheriid docodontans is likely related with a late eruption of the last lower molariform tooth. From the jaw structures associated with the dental lamina in non-mammalian cynodonts (groove and pits), the dental lamina groove is retained at least in some Gobiconodontidae and the dental lamina pits are retained in Amphidontidae.
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Free pdf:
Alexis Cornille, Kyla Beguesse, Ewan Wolff, Clemens Zinner, Patrick Asbach, François Clarac & Florian Witzmann (2025)
Skeletal pathologies in extant crocodilians as a window into the paleopathology of fossil archosaurs
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.70079
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.70079
Free pdf:
https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.70079
Crocodilians, together with birds, are the only extant relatives to many extinct archosaur groups, making them highly important for interpreting paleopathological conditions in a phylogenetic disease bracketing model. Despite this, comprehensive data on osteopathologies in crocodilians remain scarce. Here, we present the largest osteopathological survey to date of extant crocodilian skeletal material, comprising 927 individuals and 22,281 skeletal elements spanning all three extant crocodilian families. Our results reveal 1969 osteopathologies from 414 of all individuals (44.7%). Bone trauma is the most prevalent osteopathology, representing 43.9% of all pathologies observed, followed by inflammatory lesions (27.3%) and degenerative joint disorders (11.5%). Statistical analyses demonstrate significant correlations between adult body size, ontogeny, and trauma frequency, with large-sized crocodilian species and older individuals sustaining substantially more injuries. The skull, particularly the dorsal cranial aspect, showed considerably higher involvement of trauma compared to the rest of the skeleton. We also show that non-traumatic pathologies such as inflammation and degenerative joint disorders increase in larger crocodilian species and with ontogeny. These findings underscore the behavioral and physiological drivers of skeletal disease in modern crocodilians and offer key comparative data for interpreting osteopathologies in fossil archosaurs and archosauriforms.
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