Now Playing: Scientists discover rare fossil of ancient fish from Antarctica Scientists discover a new species of fossil fish from the Antarctic Ocean that predates the arrival of modern fish and whales, a team of researchers reports.
The discovery sheds light on a mysterious period when fish and other marine life evolved rapidly, but also suggests that humans could have played a role in their evolution.
The study, published online March 8 in the journal Science Advances, was led by a team led by paleoanthropologist John P. Rose at the University of New South Wales.
In the 20th century, paleo-anthropologists had long believed that fish and sharks had become extinct from the ocean by the time of the Paleocene-Eocene Thermal Maximum (PETM) in the Cretaceous Period, a period that lasted about 10 million years.
But new fossils have shown that some fish, like the modern Atlantic cod, could have thrived during this time.
Rose and his colleagues found that the cod was the first fish to evolve from a plankton-feeding ancestor called the sea cucumber.
The sea cucumbers lived in the seas off the coast of Europe about 10,000 to 15,000 years ago, when the oceans were much warmer and there was a greater supply of plankton for the animals to eat.
But these animals were still fish, because they lacked a set of teeth, called a dentition, and they could not swim.
The dentition was crucial for fish to move quickly through the water, because it helped them hold their prey in their mouths.
These fish were called “sea cucumbers,” but the new fossil evidence suggests they were not really sea cucumbums at all.
Rather, they were sea urchins.
Sea urchin teeth had to be long and thick to keep their prey inside their mouths and they were much larger than fish teeth, which are small and flexible.
Sea urchinis were so large that they had to dive underwater to get to their prey, and when they got to the surface they had no way to get back.
But when the sea ursa was exposed to oxygen, they began to grow and develop a set the teeth to allow them to eat the prey.
These sea urchase teeth had two sets of teeth that were more specialized to the food they were eating than their fish cousins, so they could hold onto the prey better.
This evolution also resulted in a shift in the body size of these fish.
Sea cucumbers now had larger brains than their predecessors, which made them much smarter.
The new fossil fossil also showed that the sea turtle ancestor of these sea usklets, called an urchinal, had a smaller brain than its cousin.
Paleoanthropologists have long believed the extinction of sea ers was a major event in the evolution of vertebrates.
But it is now clear that there were other factors at play as well, including a shift toward more efficient eating.
“The fish and sea urtle are the most abundant marine animals,” said Rose.
It turns out that these other factors, such as ocean warming and the arrival by early humans of new food sources, played a much bigger role in the extinction.
Rose and his team have now shown that these changes were a combination of factors, so a number of other factors were likely involved in the sea extinction that could not have been prevented by the ocean warming.
As a result, paleontologists now think that the extinction was more of a slow-developing process, like a gradual change in diet or lifestyle, rather than the sudden collapse of an entire species.
“There is a growing understanding of the evolution and adaptation of fish and the rise of marine life from a much larger prey resource to a much smaller prey resource,” said co-author James J. Gagnon of the University in Sydney.
“So we think the sea cycle was an important and perhaps more gradual change, rather like a long-term trend, rather that a sudden and sudden collapse.”
The study was supported by the National Science Foundation and by the Australian Research Council.
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