Fossil of 94-million-year-old sea creature is unearthed in Utah. ‘Truly significant’
A 94-million-year-old fossil found in Utah is offering new insight into the evolution of an ancient sea-dwelling reptile.
The newly discovered dinosaur, named the Sarabosaurus dahli, is the oldest of mosasaur ever found in North America, according to a June 23 news release from Utah’s Bureau of Land Management.
While finding mosasaur fossils in “younger rocks” is common, finding them in rocks exceeding 90 million years of age is a rarity, according to Alan Titus, a paleontologist with BLM.
“Finding one that preserves so much informative data, especially one of this age, is truly a significant discovery,” Titus said in the release.
The species’ name honors BLM’s longest-serving paleo volunteer, Steve Dahl, who helped in the search for the specimen, the agency said.
Sarabosaurus dahli — or “Dahl’s reptile of the mirage” — “alludes to both the ancient seaway in which this animal swam that has long since vanished and the mirages that accompany the region’s extreme summer heat,” according to the agency.
11-year journey
Working under the direction of University of North Florida professor Barry Albright, volunteer Scott Richardson was combing the Kaiparowits Formation in southern Utah when he came across something that would set off a more than decade-long journey, the university said in a June 26 news release.
In a “broad shale slope,” Richardson discovered “numerous small skull fragments and vertebrae,” which were later determined to be from an early mosasaur, the university said in a news release.
“During the time the Tropic Shale was being deposited, about 94 million years ago, mosasaurs were still very small, primitive, and in the early evolutionary stages of becoming fully marine adapted,” Albright said in the release.
As a result, finding fossils of these early reptiles is “extremely rare,” Albright said.
Following Richardson’s discovery, during the next two field seasons, both the BLM and National Park Service worked to unearth about 50% of the specimen, the agency said.
The BLM team concluded the fossil was “potentially the oldest mosasaur ever found,” but it was not confirmed until mosasaur expert Michael Polcyn of Southern Methodist University in Dallas examined the specimen, BLM said.
“I knew right away we had something special, especially considering it was so old,” Polcyn said.
New evolutionary insights
While the earliest mosasaurs were only about 3 to 5 feet long, they ultimately “evolved into gigantic lizards that dominated the oceans during the latter part of the dinosaur age,” according to the agency.
“Their land-dwelling ancestors were similar to the modern Komodo Dragon that, through time, evolved streamlined bodies, fins and shark-like tails that propelled them through the water,” the agency said.
This newly discovered species offers new evolutionary insights to the creature, according to the agency, as well as answers about “novel cranial blood supply seen in a particular group of mosasaurs.”
Typically in lizards, blood flows to the brain “with internal carotid arteries” doing the bulk of the work, BLM said.
“One group of mosasaurs that includes Sarabosaurus did something very different, shifting the primary blood supply from a branch of the internal carotid arteries to arteries entering the brain below the brain stem, a shift similarly observed in the evolution of cranial circulation in whales,” Polcyn said.
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