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A whispered, 33 billion-year-old whale could be an evolutionary "missing link"

A closer examination of the fossil found more than four decades ago led to the identification of a new type of whale – a 33-million-year-old whale that does not contain either teeth or balines. His discovery could solve a long-standing mystery about the origin of filtering whales, but some scientists say the new analysis is not entirely convincing.

Introduction Maiabalaena nesbittae, a whole new genus and species of antique whale. About the size of a modern Whale Whale, this 4.57-meter-long Chinese had no teeth or bales (rows of hair as plates used by whales to filter a small spoil from the water), but rely on suction.

As such, Maiabalaena nesbittae, which means "mother kitten", is an intermediate phase between ancient teeth whales and modern filter feeders, according to a new study published today in Current Biology.

Today, whales can be broadly merged into two main groups: whales like teeth, such as orchids and dolphins, and whales (or mysteries) that feed on a filter, such as dumbbells, birds, blue whales and whales. Baleen is a remarkable evolutionary invention that enables filtering of feeding, allowing large marine whales to consume several tons of food every day without having to squeeze or chew.

Whales are the first and only mammals that develop the bald, but the origin of this feeding strategy is not entirely clear. Whales originate from terrestrial mammals, which retain teeth after adapting to the aquatic lifestyle.

With their sharp teeth, ancient whales continued to chew their food. But the environment has changed as well as their prey, so these whales have to adopt new feed strategies. Finally, this resulted in the appearance of filtering whales.

As for how the whales went from their teeth to have a balloon – a substance made of keratin, which is that hair and nails and made from – is subject to much controversy.

Some scientists have speculated that ancient whales used their teeth to spill water and that this feeding strategy led directly to balin. This theory took a direct blow last year from palaeontologists at Monash University who showed that sharp teeth used by ancient whales can not be used as filters, concluding that ancient whales never went through the teeth-based filtration phase and that someone kind of middleman, but still-to-find species must exist.

Part of the problem is that keratin is not well preserved in fossil recordings. For paleontologists studying ancient whales, this mystery is similar to studying the flight in the old and seemingly endless quest to discover the "missing link" between floating birds and those who are capable of flying independently.

In the case of whales, paleontologists demanded a medium-sized species of whale placed between teeth whales and filtering whales. The discovery of wanton, infinite Maiabalaena nesbittae there may very much be this missing link.

Partial skeleton of Maiabalaena nesbittae, which includes an almost complete skull, was discovered in Oregon back in the 1970s, and has since appeared in the Smithsonian's national collection. To this point, a detailed analysis of the fossil was not possible because it was flooded with rocks and other materials.

The lead author of the new study, Carlos Mauricio Pedro of George Mason University and the National Museum of Natural History, reviewed the old fossil with new eyes using cutting edge CT scanning technology. By looking in the rock, the researchers were able to identify signs of revealing unblemished and silent whales – including a thin and narrow upper jaw that lacked the proper surface from which it could suspend balin.

"A lively whale whale has a large, wide roof in the mouth, and it is also thickened to create places for fastening the bales," said Pededo in a statement. "Maiabalaena it's not. We can tell you fairly that these fossil species did not have teeth, and it is more likely that it was not also that there was no baleen. "

Other evidence suggests this animal as a filter feeder. Muscular attachment of the throat bone involves the presence of strong cheeks and tongues – features that allow this whale to soak the water in the mouth, dry the fish and small squid in the process.

Equipped with this ability, these whales no longer need their chompers, and their teeth gradually disappeared. The possible loss of teeth and the origin of balin, the researchers claim, where evolutionary events are separated.

As for why the whales have fled biting and chewing in favor of sucking, researchers say it is a transition forced on them by a changing environment. Maiabalaena lived during the transition period that divided the Eocene from the oligocene, which occurred about 33 million years ago. This was a critical time for the whales, as the continents shifted and separated, and as ocean currents from Antarctica cooled the oceans.

How the geology of the planet has changed also the ocean environment – and its animals. The whale catfight changed or disappeared, forcing them to find a new booty, which resulted in a shift from teeth to suction, researchers speculate. Finally, about 5-7 million years later, about 26-28 million years ago, prostrate whales began to sprout balin, allowing another transition, this time from suction of food to filtering.

"In principle, I think this is a good study and I agree with his general conclusions," Giszmo Felix G. told. Marx, a palaeontologist at Monash University, who is not associated with this new research. "The most important thing, however, Maiabalaena it seems right in the middle of this transition, without teeth, and perhaps without baleen. "

Maybe no baleen.

That's the key phrase here. As noted, balyne, made of soft tissue, does not fossilize very well. Usually, scientists can detect the presence of balloon in the fossil, requiring traces of the corresponding blood vessels on their bones. And in fact, traces of blood vessels were discovered in Maiabalaena fossil. However, the question is whether these blood vessels are always correlated with baldness.

"The new study says no, and argues that similar structures also existed in ancient teeth whales that clearly do not filter out food," Marx said. "I agree, but this is another interpretation, and I doubt that not everyone will buy it. Luckily, there are more things we can do to tackle this issue, for example by examining how balian is actually developing in the uterus. "

University paleontologist Alistair Evans, co-author of the above-mentioned study in 2017, agrees with Marx's assessment, saying that the absence of teeth in this species is fairly evident, but the absence of balin is not so much.

"Because the bald is so rarely fossilized, his presence can rarely be seen directly," Evans told Gizmodo. "As suggested – and [as this new paper] gives more evidence – there are no silver bullets in the bones that can tell us with certainty that Balin is present. So, unfortunately, there is no strong evidence that Belen is absent, but we will also never find such evidence. "

Evans says the conclusions given in the new study are "fairly reasonable", but he would like to see other examples of this sort and related those better preserved in the region where bilin would be present.

"I was happy to find the fossils that we predicted will happen, but the evidence is not fooling that really fit into this slot," Evans added.

That's right Maiabalaena nesbittae the missing link we are looking for? Quite possibly yes – but we will not know for sure until more fossils are recovered.

[Current Biology]

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