Freshwater mosasaur tooth from Hell Creek Formation, North Dakota (free pdf)
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Ben Creisler
Dec 12, 2025, 1:28:02 PM (6 days ago) Dec 12
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Ben Creisler
Sea reptile’s tooth shows that mosasaurs could live in freshwater
https://www.uu.se/en/press/press-releases/2025/2025-12-12-sea-reptiles-tooth-shows-that-mosasaurs-could-live-in-freshwater
https://www.eurekalert.org/news-releases/1108926
https://www.iflscience.com/it-was-bigger-than-a-killer-whale-66-million-year-old-tooth-suggests-mosasaurs-were-hunting-in-rivers-not-just-seas-81880
https://www.discovermagazine.com/a-marine-predator-the-size-of-a-bus-patrolled-ancient-rivers-66-million-years-ago-48389
***
Palaeocast Episode 171: Freshwater Mosasaurs, with Nathan Van Vranken and Melanie During
A new paper:
Free pdf:
Melanie A. D. During, Nathan E. Van Vranken, Clint A. Boyd, Per E. Ahlberg, Suzan J. A. Warmerdam-Verdegaal & Jeroen H. J. L. Van der Lubbe (2025)
“King of the Riverside”, a multi-proxy approach offers a new perspective on mosasaurs before their extinction
BMC Zoology 10: 25
doi: https://doi.org/10.1186/s40850-025-00246-y
https://link.springer.com/article/10.1186/s40850-025-00246-y
The discovery of a mosasaurine tooth (NDGS 12217) in the Hell Creek Formation, Morton County, North Dakota, adds to the growing evidence that mosasaurs, traditionally considered marine reptiles, could inhabit freshwater environments. This tooth was found in a context devoid of other marine taxa, suggesting the individual may have ventured into freshwater environments. The morphology of the tooth supports a conservative referral to the tribe Prognathodontini, and stable isotope analyses on carbonate and phosphate fractions of tooth enamel, along with 87Sr/86Sr ratios, indicate a freshwater origin. These findings challenge the notion of mosasaurs as exclusively marine predators, highlighting their potential ecological flexibility during the Late Maastrichtian. This study employs a multi-proxy approach to compare the tooth’s isotopic signatures with other taxa from the same and nearby formations (including teeth of other mosasaurines), providing insights into the environmental transitions of the Western Interior Seaway (WIS) towards the end of the Cretaceous. This comprehensive approach aims to provide deeper insights into the behavior, ecology, and potential migratory patterns of mosasaurs beyond their known marine habitats, enhancing our understanding of their adaptation to rapidly changing environments during the Late Cretaceous.
Melanie A. D. During, Nathan E. Van Vranken, Clint A. Boyd, Per E. Ahlberg, Suzan J. A. Warmerdam-Verdegaal & Jeroen H. J. L. Van der Lubbe (2025)
“King of the Riverside”, a multi-proxy approach offers a new perspective on mosasaurs before their extinction
BMC Zoology 10: 25
doi: https://doi.org/10.1186/s40850-025-00246-y
https://link.springer.com/article/10.1186/s40850-025-00246-y
The discovery of a mosasaurine tooth (NDGS 12217) in the Hell Creek Formation, Morton County, North Dakota, adds to the growing evidence that mosasaurs, traditionally considered marine reptiles, could inhabit freshwater environments. This tooth was found in a context devoid of other marine taxa, suggesting the individual may have ventured into freshwater environments. The morphology of the tooth supports a conservative referral to the tribe Prognathodontini, and stable isotope analyses on carbonate and phosphate fractions of tooth enamel, along with 87Sr/86Sr ratios, indicate a freshwater origin. These findings challenge the notion of mosasaurs as exclusively marine predators, highlighting their potential ecological flexibility during the Late Maastrichtian. This study employs a multi-proxy approach to compare the tooth’s isotopic signatures with other taxa from the same and nearby formations (including teeth of other mosasaurines), providing insights into the environmental transitions of the Western Interior Seaway (WIS) towards the end of the Cretaceous. This comprehensive approach aims to provide deeper insights into the behavior, ecology, and potential migratory patterns of mosasaurs beyond their known marine habitats, enhancing our understanding of their adaptation to rapidly changing environments during the Late Cretaceous.
***
News:
Sea reptile’s tooth shows that mosasaurs could live in freshwater
https://www.uu.se/en/press/press-releases/2025/2025-12-12-sea-reptiles-tooth-shows-that-mosasaurs-could-live-in-freshwater
https://www.eurekalert.org/news-releases/1108926
https://www.iflscience.com/it-was-bigger-than-a-killer-whale-66-million-year-old-tooth-suggests-mosasaurs-were-hunting-in-rivers-not-just-seas-81880
https://www.discovermagazine.com/a-marine-predator-the-size-of-a-bus-patrolled-ancient-rivers-66-million-years-ago-48389
***
Palaeocast Episode 171: Freshwater Mosasaurs, with Nathan Van Vranken and Melanie During
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