Frozen over time: fossils of nearly 300 fish preserved in limestone suggest that they have been swimming in schools for at least 50 million years
- Researchers discovered fossil fish in large groups at the Green River formation
- Most fish look in the same direction and are close to each other
- Simulations of the fish and water stream suggest that they were swimming in formation
A piece of limestone with the impressions of nearly 300 fish has captured what a school was swimming in harmony 50 million years ago.
Although it is known that many animals, from birds and fish to insects, travel in formations, just as this behavior originated in the evolutionary timeline is not yet certain.
The fossil discovery of the Green River Formation that stretches across Colorado, Wyoming and Utah can finally provide a glimpse of insight, suggesting that it dates back at least as far back as the Eocene age.
Careful examination of the mat revealed as many as 259 fossilized fish, all identified as the small extinct species, Erismatopterus levatus. It is unclear how exactly they died
Researchers from Arizona State University and the Oishi Fossils Gallery of the Mizuta Memorial Museum in Japan describe the findings in a new paper published in Proceedings of the Royal Society B.
Careful examination of the mat revealed as many as 259 fossilized fish, all identified as the small extinct species, Erismatopterus levatus.
It is unclear how exactly they died, but the researchers say the evidence suggests that they were all in the same place at the time of the event.
And their demise took place & # 39; almost instantaneously & # 39 ;.
& # 39; Given that dead bodies in a collection of cadavers would be placed anywhere on the plate, the observed localized aggregation is probably more the result of behavior than of an artifact of fossilization, & # 39 ;, the researchers note in the paper.
& # 39; The sediment is also fine-grained mud, which is a criterion for an in situ rather than a transported assembly. & # 39;
The fossil discovery of the Green River Formation that stretches across Colorado, Wyoming and Utah can finally provide a glimpse of insight into school behavior, suggesting that it dates back at least as far back as the Eocene age
To better understand what may have happened, the researchers have simulated 1000 possible scenarios incorporating fish measurements, as well as different types of water flow and spatial distribution.
And these simulations suggest that they swam in uniform as fish do today.
By sticking together in a group (or shoaling), the small fish could help protect against predators, the researchers note.
& # 39; Because we have found remote evidence in our fossilized group of E. levatus, we can reasonably deduce predator avoidance as a selective pressure that leads to shoaling behavior & # 39 ;, write the researchers.
& # 39; Accordingly, the density within the group was higher in the safer central area, while it was lower at the edge of the group, where predators often attack. & # 39;
A piece of limestone with the impressions of nearly 300 fish has captured what a school was swimming in harmony 50 million years ago. Although it is known that many animals travel in formations, it is not certain at the time that this behavior occurred
WHEN WERE THE & # 39; BIG FIVE & # 39; EXTINCTION EVENTS OF THE EARTH?
Scientists have traditionally referred to the massive extinctions of the & # 39; Big Five & # 39 ;, including perhaps the most famous mass extinction caused by a meteorite impact that brought about the end of the dinosaurs 66 million years ago.
But the other major mass extinctions were caused by phenomena that come entirely from Earth, and although they are less well known, we can learn something from exploring them that could shed light on our current environmental crises.
- The late Ordovician: This old crisis around 445 million years ago saw two big waves of extinction, both caused by climate change due to the advance and withdrawal of ice caps in the southern hemisphere. This makes it the only major extinction to be linked to global cooling.
- The Late Devonian: This period is now considered a number of & # 39; pulses & # 39; of extinction spread over 20 million years, starting 380 million years ago. This extinction is linked to a major climate change, possibly caused by an eruption of the Viluy Traps volcanic area in today's Siberia. A major eruption may have led to rapid fluctuations in the sea level and reduced oxygen levels in the oceans.
- The middle Perm: Scientists recently discovered another event 262 million years ago that is the size of the & # 39; Big Five & # 39; equals. This event coincided with the Emeishan eruption in what is now China, and is known to cause simultaneous extinction in the tropics and higher latitudes.
- The late Perm: The massive extinction of the late Permian, about 252 million years ago, makes all other events deaf, with about 96% of the species extinction. The extinction was caused by a huge eruption of Siberian traps, a gigantic and long-lasting volcanic event that covered much of modern Siberia, leading to a succession of environmental impacts.
- The late triad: The Late Trias event, 201m years ago, has a number of similarities with the Late Perm event. It was caused by another large-scale eruption, this time from the Central Atlantic Magmatic Province, which announced the split of the supercontinent Pangea and the first opening of what would later become the Atlantic.
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