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Toothless, 33-Million-Year-Old Whale Could Be Evolution & # 39; Loss of Links & # 39;



A closer examination of the fossils discovered more than four decades ago has led to the identification of a new species of whale – a 33 million year old cetacea that has neither teeth nor baline. His findings could solve the old mystery of the origin of filter-eating whales, but some scientists say the new analysis is not entirely convincing.

Introduce Maiabalaena nesbittae, genus and new species of ancient whales. About the size of a modern beluga whale, this 4.57m cetacean does not have teeth or balin (a row of hair-like plates used by whales to filter small prey from water), relying solely on suction feeding.

Therefore, Maiabalaena nesbittae, which means "mother whale," representing the intermediate stage between ancient toothed whales and modern filter feeders, according to a new study published today in Current Biology.

Today, whales can be broadly integrated into two main groups: toothed whales, such as orcas and dolphins, and filter-eating (or mystic) whales, such as humpback whales, fin whales, blue whales, and minke whales. Baleen is a remarkable evolutionary discovery that allows the administration of filters, allowing large sea whales to consume several tons of food every day without having to chew or chew.

The pope is the first and only mammal to evolve into baleen, but the origin of this eating strategy is not entirely clear. Whales come from land mammals, which retain their teeth after adapting to an aquatic lifestyle.

With their sharp teeth, ancient whales continued to chew their food. But the environment changes, as does their prey, so the whale must adopt a new feeding strategy. Finally, this results in the appearance of filter-eating whales.

As how fish change from having teeth to baleen – a substance made of keratin, made of hair and nails – is the subject of a lot of controversy.

Some scientists speculate that ancient whales used their teeth to filter water, and that this feeding strategy led directly to balin. The theory was hit directly last year by Monash University paleontologist who showed that sharp teeth used by ancient whales could not be used as filters, concluding that ancient whales never passed the tooth-based filtration phase, and such an intermediate species, which had not yet been discovered, had to there is.

Part of the problem is that keratin is not properly stored in the fossil record. For palaeontologists who study ancient whales, this mystery is similar to flight studies in ancient animals, and the seemingly endless search for "missing links" between flying birds and those capable of flying alone.

In the case of whales, paleontologists have searched for species between whales that are positioned between toothed whales and filter-eating whales. Toothless, baleenless discovery Maiabalaena nesbittae it can become this missing link.

Partial framework Maiabalaena nesbittae, which includes an almost complete skull, was discovered in Oregon in the 1970s, and has languished in the Smithsonian national collection ever since. At this point, a detailed analysis of the fossils was impossible because it was flooded with rocks and other materials.

The lead author of the new study, Carlos Mauricio Peredo of George Mason University and the National Museum of Natural History, looked at these old fossils with new eyes using state-of-the-art CT scan technology. Peering into the rock, researchers were able to identify signs of a toothless and baleenless whale – including a thin and narrow upper jaw that did not have the right surface to suspend baleen.

"Living balin whales have large and wide roofs in their mouths, and they also thicken to create additional sites for ballet," Peredo said in a statement. "Maiabalaena not. We are quite convincing to say that this fossil species does not have teeth, and most likely it does not have baleen as well. "

Other evidence shows this animal as a filter feeder. Muscle attachment to the bones of his throat implies the presence of strong cheeks and retractable tongue – a characteristic that allows this whale to suck water into its mouth, braking small fish and squid in the process.

Equipped with this ability, these whales no longer need their chompers, so their teeth gradually fade. Tooth decay and the origin of baleen, the researchers, debated, where a separate evolutionary event took place.

Like why toothed whales don't bite and chew for the sake of sucking, the researchers say it is a transition that is forced on them by a changing environment. Maiabalaena lived during the transition period which divided the Eocene from the Oligocene, which occurred around 33 million years ago. This is a critical time for the pope, when continents shift and separate, and when ocean currents from Antarctica cool the ocean.

When the planet's geology changes, so does the marine environment – and its animals. Toothed whale prey changes or disappears, forcing them to find new prey, which results in a transition from toothed to suction feeding, the researchers speculate. Finally, around 5-7 million years later, around 26-28 million years ago, toothless whales began to sprout, facilitating other transitions, this time from suction feeding to feeding filters.

"In general, I think this is a good study, and I agree with the general conclusion," Felix G. Marx, a paleontologist at Monash University who is not affiliated with this new research, told Gizmodo. "Very important, though, Maiabalaena it seems right in the middle of this transition, without teeth, and may not have balin. "

Maybe there is no baleen.

That is the key phrase, here. As noted, baleen, which is made of soft tissue, does not fossil very well. Normally, scientists can detect the presence of baleens in fossils by searching for traces of blood vessels that are suitable for their bones. And in fact, blood vessel traces are detected inside Maiabalaena fossil. The question, however, is whether these vessels always correlate with balin.

"The new study says no, and argues that similar structures also exist in ancient toothed whales that clearly do not filter feed," said Marx. "I agree, but this is still an interpretation, and I don't think everyone will buy it. Fortunately, there are many things we can do to address this question, for example by examining how baleen really develops in the womb."

Monash University paleontologist Alistair Evans, a writer from the 2017 study, agrees with Marx's judgment, saying the absence of teeth in this species is quite clear, but the absence of baleen, not so much.

"Because baleen is very rarely petrified, its presence can rarely be seen directly," Evans told Gizmodo. "As suggested earlier – and [as this new paper] provide more evidence – there are no silver bullets in the bones that can tell us to make sure that baleen is present. So unfortunately there is no strong evidence that baleen does not exist, but we also will never find such evidence. "

Evans said the conclusions made in this new study were "quite reasonable," but he wanted to see other specimens from this species and related species that were better preserved in areas where baleen would exist if there were any.

"I am glad that they found fossils that we predicted would happen, but the proof is not the slam dunk that really fits in this slot," Evans added.

So is Maiabalaena nesbittae the missing link we've been looking for? Very likely yes – but we will not know for sure until more fossils are found.

[Current Biology]

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