July 21, 2024

Paleontologists are unearthing part of what the world was like before us before the great extinction. And in that work, they discovered the fossils of two species of sturgeon fish (two of each) in an incredible state of conservation in a place called “Tanis”.

This corresponds to a section of the Hell Creek Formation of North Dakota, USA once home to a large, deep river that fed the Western Interior Seaway that stretched from the Gulf of Mexico to the Arctic Ocean.

These are fossils from the Cretaceous period, which corresponds to the last of the Mesozoic era, and which ended 66 million years ago.

The researchers named one of the discovered species Acipenser praeparatorum (“acipenser” means “sturgeon” in Latin, and “praeparatorum” translates as “to prepare”, in honor of the team that prepared the fossil prior to its investigation.

the other species Acipenser amnisinferos or the “Hell’s Creek Sturgeon”. Both species of fish are extinct today. However, they bear an unexpected resemblance to the modern sturgeon that is native to East Asia and Europe, rather than North America, study co-author Eric Hilton, an evolutionary biologist at the Virginia Institute of Marine Sciences, told Live Science.

The study was published on October 3 in the Journal of Paleontologyand concludes that both species They lived and died alongside the dinosaurs.

66 million years ago, the Chicxulub asteroid crashed into the earth, hitting the coast of Yucatan causing one of the great extinctions of the planet. “Some paleontologists believe that it caused the extinction of 70% of the species on Earth. says the study. And with this, Tanis became the graveyard for thousands of freshwater species that were immediately buried at the moment of extinction.

This is why, for the researchers, finding these species in such good condition “was really amazing,” Lance Grance, a paleontologist at the Field Museum in Chicago and co-author of the study, told WordsSideKick.com. “I mean, [los peces] They were stacked like firewood.”

The find sheds clues to the history of freshwater fish in North America in the Late Cretaceous period, which is poorly represented in the fossil record. In addition, it tells of the shocking effects of the Chicxulub asteroid, which hit the Yucatan coast in Mexico and its repercussions reached North Dakota.

“Although the Cretaceous is widely regarded as a time of great evolutionary transition for the freshwater fish fauna of North America, the fossil record from this period is notoriously poor and consists mainly of fragments and isolated skeletal elements”, says the study.

Psammorhynchus longipinnis fossil, other species that have been discovered at the site. Photo: Journal of Paleontology.

In contrast to most known sturgeon fossils from the Cretaceous period, which are represented only by poorly preserved bone fragments or partial skeletons, these had something special: Almost all of the creatures’ bony outer coverings, or shields, were intact and impeccably preserved.

These specimens help fill a gap in the fossil record: “They have a lot of clear similarities to sturgeon, which makes them easy to identify,” Grande said. “But they have several unique features that allow us to describe them as something new.”

Sturgeons are a type of fish that have existed for 200 million years. This species is characterized by having “large bony plates on the outside,” study co-author Eric Hilton, an evolutionary biologist at the Virginia Institute of Marine Sciences, explained to WordsSideKick.com.

These plates protect the carcasses of the fish so that they are not destroyed by the waves or currents. Scientists suspect that on the day these fish died they were victims of a huge tidal wave that carried thousands of pounds of sediment into the river, immediately burying them.

“The fish we describe they were so well preserved because they were probably buried alive or at least immediately after their deathGrande told Newsweek. Therefore, all the bones are still articulated with each other in the fossil specimens.

Full body fossil of Acipenser praeparatorum. Photo: Journal of Paleontology.

The two newly described species add to the taxonomic and morphological diversity of Acipenseridae known from the Late Cretaceous of North America. “This is incredible,” Hilton said, “but it’s the tip of the iceberg.”

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