North Dakota
Scientists discover ancient river-dwelling mosasaur in North Dakota
Some 66 million years ago, a city bus-sized terrifying predator prowled a prehistoric river in what is now North Dakota.
This finding is based on the analysis of a single mosasaur tooth conducted by an international team of researchers from the United States, Sweden, and the Netherlands.
The tooth came from a prognathodontine mosasaur — a reptile reaching up to 11 meters long. This makes it an apex predator on par with the largest killer whales.
It shows that massive mosasaurs successfully adapted to life in rivers right up until their extinction.
Isotope analysis
Dating from 98 to 66 million years ago, abundant mosasaur fossils have been uncovered in marine deposits across North America, Europe, and Africa.
However, these marine reptile fossils have been rarely found in North Dakota before.
In this new study, the large mosasaur tooth was unearthed in a fluvial deposit (river sediment) in North Dakota.
Its neighbors in the dirt were just as compelling: a tooth from a Tyrannosaurus rex and a crocodylian jawbone. Interestingly, all these fossilized remains came from a similar age, around 66 million years old.
This unusual gathering — sea monster, land dinosaur, and river croc — raised an intriguing question: If the mosasaur was a sea creature, how did its remains end up in an inland river?
The answer lay in the chemistry of the tooth enamel. Using advanced isotope analysis at the Vrije Universiteit in Amsterdam, the team compared the chemical composition of the mosasaur tooth with its neighbors.
The key was the ratio of oxygen isotopes.
The mosasaur teeth contained a higher proportion of the lighter oxygen isotope than is typical for mosasaurs living in saltwater. This specific isotopic signature, along with the strontium isotope ratio, strongly suggests that the mosasaur lived in a freshwater habitat.
Analysis also revealed that the mosasaur did not dive as deep as many of its marine relatives and may have fed on unusual prey, such as drowned dinosaurs.
The isotope signatures indicated that this mosasaur had inhabited this freshwater riverine environment. When we looked at two additional mosasaur teeth found nearby, slightly older sites in North Dakota, we saw similar freshwater signatures. These analyses show that mosasaurs lived in riverine environments in the final million years before going extinct,” explained Melanie During, the study author.
Transformation of the Seaway
The adaptation occurred during the final million years of the Cretaceous period.
It is hypothesized that the mosasaurs were adapting to an enormous environmental shift in the Western Interior Seaway, the vast inland sea that once divided North America.
Increased freshwater influx gradually transformed the ancient sea from saltwater to brackish water, and finally to mostly freshwater, similar to the modern Gulf of Bothnia.
The researchers hypothesize that this change led to the formation of a halocline: a structure where a lighter layer of freshwater rested atop heavier saltwater. The findings of the isotope analyses directly support this theory.
The analyzed mosasaur teeth belong to individuals who successfully adapted to the shifting environments.
This transition from marine to freshwater habitats (reverse adaptation) is considered less complex than the opposite shift and is not unique among large predators.
Modern parallels include river dolphins, which evolved from marine ancestors but now thrive in freshwater, and the estuarine crocodile, which moves freely between freshwater rivers and the open sea for hunting.
Findings were published in the journal BMC Zoology on December 11.
MAPLETON, N.D. (Valley News Live) – Casselton Fire responded to a shop fire in rural Mapleton on Saturday afternoon, according to Casselton Fire Chief John Hejl.
Casselton Fire was dispatched to the scene at 3:30 p.m. Saturday. Windy conditions escalated the fire before crews arrived, Hejl said.
Firefighters used defensive and offensive lines to control the fire upon arrival.
Casselton Fire was assisted by Cass County Sheriff’s Office, Casselton Ambulance, West Fargo Police Department, Davenport Fire and Mapleton Fire.
Copyright 2026 KVLY. All rights reserved.
A do not use water advisory issued by the City of Finley, North Dakota. April 2026.
FINLEY, N.D. (KFGO) – The city of Finley, North Dakota has been without potable water since Friday due to a suspected water main leak. Steele County Emergency Management says it is unclear how long it will take to restore water services in the city.
The North Dakota Department of Environmental Quality says the available water in Finley has been deemed unusable for drinking, cooking, bathing and washing dishes or laundry.
The water system will need to be flushed and samples that say the water is safe will need to be collected for the water advisory to be lifted.
Richard D. “Rick” Langowski, age 78 of Minto, North Dakota passed away on Thursday, April 16, 2026 at his home in Minto.
Rick was born March 10, 1948 in Grafton, North Dakota, the son of the late Julian and Catherine (Wysocki) Langowski. In 1967, he volunteered for the military bringing him to Germany as a Motor Sargent. After an Honorable Discharge he took a job at the International Airport in Grand Forks, ND. His duties included: refueling planes and jets as well as maintaining the grounds. He had the opportunity to meet the famous singer Mr. James Brown.
Rick was united in marriage to Alice Odegard on June 17, 1982 in Minto, North Dakota. The family made their home in Minto where they raised Jason and Angela. Rick was very proud of his children and loved them more than anything. He told everyone and bragged about the children he raised. He cherished his grandchildren and loved to be present in every aspect of their lives.
His career changed to semi driving where he drove for Cenex Transportation for four years and ten years for Valley Transports. His love for the open road directed him into the used car business. He opened Minto Auto Sales and Services in 1987, proudly operating for 39 years. He had the privilege to meet many people and travel to many places. He enjoyed riding his many Harley Davidson Motorcycles. In 2025, he sold the business to his longtime mechanic and friend, Aaron Anderson. In Rick’s opinion, “Minto Auto is one of the best mechanical shops in the area.”
He was a member of the Sacred Heart Catholic Church, Minto, ND. He loved hunting with Jason, watching sports, especially the Yankees and Twins. In 2017, Rick was able to enjoy a father/son trip of a lifetime to Alaska. He thoroughly enjoyed every aspect of the trip and thought was the best time of his life.
Rick is survived by his children: Jason Odegard, Reynolds, ND; Angela (Nick) Eppert, Goshen, IN; grandchildren: Ashlyn, Kaia, Annika, Boden and Caelan; sisters: Carol King, Grand Forks, ND; Connie Jones, Argyle, MN; seven nieces and nephews. He is also survived by his very close friend and confidant, Yvette Estep, Grafton, ND. He was preceded in death by his parents and siblings: Robert and Ronald.
Rick’s family would like to extend a very special thank you to Yvette Estep, an employee of Rick’s, affectionately known as “hotrod.” She was there for Rick, along with Aaron for doctor’s appointments, treatments and helped comfort him throughout his battle. Jason and Angela will be forever indebted to her and consider her family.
Mass of Christian Burial will be Wednesday, April 22, 2026 at 10:30 A.M. at the Sacred Heart Catholic Church of Minto. Visitation will be for one hour prior to the service at the church. Interment will be at the Sacred Heart Catholic Cemetery, Minto, ND. Military Rites will be provided by the Minto American Legion Post and the North Dakota National Guard Honor Guard.
or send flowers to the family in memory of Richard D. Langowski, please visit our
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