Fossils show adaptations – such as depressible teeth, complex jaw structures and cold tolerance – which indicate the initial evolution of these fish to adapt to life in the cold.
Fossils of the oldest known relatives of salmon and carp were discovered well above the Arctic Polar Circle, an environment with months of darkness in winter and cold temperatures.
Using Tip 3D Image Technology, Lisa Van Loon and Neil Banerjee, from Western Universityin Canada, they analyzed fossilized bones of fish found in the rocks of Prince Creek formation in Alaska to reveal a so far unknown polar ecosystem that traces upper Cretaceous.
The findings were published in the magazine the Europa Press agency reported on Wednesday.
“These findings suggest that this remote region may have been an evolutionary launch platform for the fish that now dominate Northern rivers and lakes worldwide,” said Van Loon, an investigative professor in the Western Earth Sciences and Anthropology departments, quoted in a statement.
Some of the fossils discovered in Alaska were little larger than the head of a pin and were deeply embedded in the rock.
The traditional preparation of fossils, which implies careful manual extraction of surrounding sediments, was not an option, as specimens were simply too fragile.
Analysis allowed to identify entirely new species
Using microsinchrotron computed tomography technology (Micro-CT) at Advanced Proton Source, with the support of Canadian Light Source, the researchers digitized rocks containing fossils without physically disturbing them.
Ultra-sprout and high resolution x rays allowed them to digitally reconstruct the anatomy of these 3D old fish, revealing complex structures as jaws, teeth and fin rays with an extraordinary detail.
“Many of these fossils were so delicate and so deeply embedded in the rock that traditional preparation would have destroyed them,” said Banerjee, professor of land sciences at Western.
What species were discoveries?
The analysis allowed identify entirely new speciessome of which represent the first known members of the fish groups that now dominate the northern rivers and lakes, such as salmon, carp and Lucius.
Subvulusalm Alaskensis, which means “Alaska First Salmon” in Iñupiaq, the Inuit language, is now the oldest known member of the Salmon Family, eclipsing previous records in almost 10 million years.
The first known cypriniformpart of the same group of modern fish and carp, marking their first appearance in North America (previously found only in Asia and Europe).
Newly discovered species of liquid -like fish They also lived at Prince Creek Formation about 73 million years ago, including ArchaeosiiLik Gilmulli and Nunikuluk Gracilis, successfully adapting to Arctic winters.
Sharks like the Squatina (relative of the angel shark), In the Esturjõgi River e fish-fish They were also discovered in the fossil samples.
How they adapted to life in the cold?
These old fish were surviving. At the end of the Cretacic, the Arctic went through four months of total darkness each year, with average annual temperatures of about 6 ° C and cold winters.
Fossils show adaptations – as depressible teeth, complex jaw structures and cold tolerance – which indicate the initial evolution of these fish to adapt to life in the cold.
“This discovery changes our understanding of the evolution of fish. Suggests that high latitudes ecosystems, but Alaska, not only received southern species, but also created them,” said Banerjee.
This study supports the idea of a specific Arctic Ecosystem, known as Paanaqtat Province, where unique animals – dinosaurs, mammals and now fish – evolved in isolation.
