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The gloomy, 33-million-year-old kit can be an evolutionary & # 39; missing link & # 39;



A closer look at the fossil that was found more than four decades ago led to the recognition of a new type of whale – a 33 million year old whale that had no teeth or baleen. Her discovery could solve a long-lasting secret about the origins of filter feeding whales, but some scientists say the new analysis is not entirely convincing.

Introducing Maiabalaena nesbittae, a brand new genre and an ancient type of whale. About the size of a contemporary whalebone whale, this caviar 4.57 feet long did not have teeth or baleen (thin hair ropes used by the whales to filter tiny buckwheats from the water), relying instead on sucking the food.

Like that, Maiabalaena nesbittae, meaning "mother-of-pearl whales", represents the middle stage between old toothed whales and modern filtration, according to new research published in Current Biology.

Today, whales can be broadly classified into two main groups: toothed whales, such as orcs and dolphins, and whales (or mystics) feeding on filters, such as humpbacks, Finnish whales, blue whales and mine kits. Baleen is a remarkable evolutionary invention that allows the feeding of filters, allowing large whales to consume a few tons of food each day without having to embed or chew.

Whale is the first and only mammal developing baleen, but the source of this feeding strategy is not entirely clear. Kits originate from terrestrial mammals who retained their teeth after adapting their water-lifestyle.

With their toothbrushes, ancient whales continued to chew food. But the environment has changed as well as their prey, so these whales have had to adopt new feeding strategies. In the end, this resulted in the emergence of a filter feeding whale.

As for the way whales have gone from their teeth to having a balean – a substance from keratin, which is that hair and nails and made of them – is subject to many controversies.

Some scientists have speculated that ancient whales used water-repellent teeth and that this feeding strategy led to direct bale. This theory was directly hit by Monash University paleontologists last year, who showed that the sharp teeth of western whales could not be used as filters, concluding that ancient kits never passed through the filtration phase of the tooth and that some kind of indirect, still-found species must exist .

Part of the problem is that keratin is not kept well in the fossil record. For paleontologists who study ancient kits, this mystery is similar to studying the escape in old animals and seemingly endless quest for discovering "missing links" between sailing birds and those capable of flying with their own motor.

In the case of whales, paleontologists asked for medium types of whales located between the whipping kits and the feed fed whiskers. Discovery painless, baleenless Maiabalaena nesbittae it might be a good link missing.

Partial skeleton Maiabalaena nesbittae, which includes a nearly complete skull, was discovered in Oregon in the 1970s and has since shattered in Smithsonian's national collection. Until this point a detailed fossil analysis was not possible because it was flooded with stone 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 this old fossil with new eyes using contemporary CT scanning technology. By studying the rock, the researchers have been able to identify the signs of a toothless toothache without baleenes – including the thin and narrow upper jaw that did not have the appropriate surface to sever the baleen.

"The Life Bale Kit has a large, wide roof in the mouth, and is also thick to create baleen attachments," Peredo said in a statement. "Maiabalaena not. We can proudly say that these fossil species do not have teeth, and there is probably no baleal. "

Other evidence points to that animal as a filter investor. Knotted muscles on the bones of the throat imply the presence of strong cheeks and retractable tongue – features that would allow this kite to suckle water in the mouth, feeding on fish and small squid in that process.

Equipped with that ability, these kits no longer had the need for their reconciliation, so their teeth gradually faded. The final loss of teeth and the origin of the baleenes, claim researchers, where they are therefore a separate evolutionary event.

As for abandoned whales who have abandoned chewing and chewing in favor of sucking, researchers say that transition is forced to change the environment. Maiabalaena lived during the transitional period that divided the eocene from the oligocene, which occurred some 33 million years ago. This was a critical time for whales, while the continents moved and separated, and how the ocean's current from the Antarctica cooled the oceans.

As the geology of the planet has changed, so is the ocean environment – and animals. The kelp of the toothed whales changed or disappeared, forcing them to find a new prey, resulting in a transition from dental to suction to food, investigating scientists. Finally, around 5-7 million years later, about 26 to 28 million years ago, no tooth whales began to bite into the balean, which facilitated another transition, this time from cooling to intake to food filtration.

"In general, I think this is a good study and I agree with its general conclusions," said Gizmodo Felix G. Marx, paleontologist at Monash University who is not related to these new research. "However, Maiabalaena it seems to be in the middle of this transition, without teeth, and perhaps without baleenes. "

Maybe there is no baleen.

It's a key phrase here. As noted, baleen, made of soft tissue, does not fossilize very well. Typically, scientists can detect the presence of baleenes in fossils searching for traces of appropriate blood vessels on their bones. And in fact, blood vessel traces were discovered in Maiabalaena fossil. The question, however, is whether these blood vessels are always associated with the Balean.

"The new study says no, and claims that similar structures also existed in ancient gnawing kits that apparently did not filter food," Marx said. "I agree, but this is still an interpretation, and I doubt that not everyone will buy in it. Fortunately, there are more things we can do to resolve this issue, for example by examining how baleen actually develops in the womb."

Monash University Paleontologist Alistair Evans, co-author of the above mentioned 2017 study, agrees with Marx's estimate, saying the absence of teeth in this type is quite obvious, but the lack of baleenes, not so much.

"Since the Baleen is so seldom fossilized, its presence can rarely be seen directly," Evans Gizmoda said. "As already suggested – and [as this new paper] gives more evidence – there are no silver bullets in the bones that could certainly tell us that baleen is present. Unfortunately, there is no strong evidence that the Baleen was absent, but we will never find such evidence. "

Evans says the conclusions in the new study are "fairly reasonable," but would also like to see other samples of this kind and related species that are better preserved in the region where the baleen would be present, if present.

"I was fortunate to find the fossil that we have foreseen, but the evidence is not a joke that he really did agree on this slot," Evans added.

That's right Maiabalaena nesbittae missing the link we are looking for? Very likely – but we will certainly not know until more fossils recover.

[Current Biology]

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