Ostriches, emus, rheas and other large, flightless birds are located on six lands separated from the sea, but the way in which such a distant apart location was reached without the ability to fly remains a permanent mystery.
One idea was that the ancestors of this group of birds known as the Paleognaths had just walked to the location where most planets were used together as Supercontinent Pangaea (320-105 million years ago), and when this huge land split, the birds were already in those places.
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To resolve what happened, Clara Widrig, a vertebrate zoologist at the Smithsonian National Museum of Natural History in Washington, DC, and her colleagues analyzed specimens of ancient Peregunas Litonis. It lived between 59-56 million years ago, but it is the oldest fossil ancient cont seen in such an untouched condition.
“It’s not certain if Litonis is a direct ancestor of our living Peregunas. It’s entirely possible that no true ancestor has been discovered yet, but it represents our best guess as to what our ancestors look like,” Widrig told Live Science.
Previous investigations of the slightly distant associated Lithornithid conserved feathers called Calciavis Grandei showed that it could be flying, but it was not clear to what extent. No one did a quantitative analysis of lisolnitide bone shape to answer that question.
Related: Do ostriches really bury their heads in the sand?
Therefore, in a new study published on Wednesday (September 17), Widrig and her colleagues published in a letter from Journal Biology, L. We compared the sternum or sternum shapes with the shapes of living birds and used a three-dimensional geometric dataset to solve how well the animals flew.
“The sternum is extremely important for flight because it’s where the big pectoral muscles are fixed,” Widrig said.
The shape of the sternum indicates that it could have been able to handle aerobic flapping flight styles that allow for long flights.
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“We found the shape of the sternum really resembles the shape of a living bird that can fly very long distances across the ocean, like the great whites and herons,” Widrig said.
“This is very interesting because the great huglet is a cosmopolitan species in terms of moving from one continent to another,” said Peter Hosner, a bird curator at the Museum of Danish History, who was not involved in the work.
“That kind of species are actually very rare in birds,” he told Live Science. “We are biased in the Northern Hemisphere, where many birds travel and cover long distances. But worldwide, most birds are residents on one continent, an island or a small area and don’t move much.”
This discovery suggests that ancient Peregunas may have flew to distant land, establishing a population that later evolved independently into the large, generally flightless birds we know.
“It seems like an epic case of convergent evolution,” Hosner said.
Today there are about 60 species of live Paleognaths. They include around 45 species of Tinamo (which can fly in short bursts like pheasants), up to five species of Kiwi, one species of emu, three species of cassouri, two species of ostriches, and one or two species of rare.
“In order for a bird to fly, it needs to meet two conditions,” she said. “For example, you can’t rely on food in the trees because you have to be able to put all your food on the ground, and there are no predators who need to fly to get away.”
Recently, it would have only happened in predation-free island environments, such as the dodo (Raphus cucullatus), Widrig said. However, it was very different after the Cretaceous-phylogenetic extinction events wiped out non-bird dinosaurs about 66 million years ago.
“The world was generally dismissed from predators, and mammal predators hadn’t evolved yet. So birds feeding the ground had free paths to become essentially flightless,” Widrig said. “Flights are a lot of work and it’s much easier to have no room for flight unless you have to escape from anything.
When larger predators appeared, she said the flightless bird would have had time to adapt by becoming either bigger and intimidating like a cassowire or quick runners like an ostrich.
However, all these similar changes evolved independently. “They went on a conference call with each other and said, ‘Okay, you’re going to Africa, you’re going to evolve into an ostrich. I’m going to South America. I’m going to evolve into a rare,” Widrig said.
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