A New Study Helps to Explain the Evolution of Flightless Birds

Chardynne Joy H. ConcioApr 07, 2019 09:46 PM EDT

Large flightless birds are scattered across all but one of the world's southern continents. Since Darwin's era, people have wondered: How are they related? Ostriches, emus, cassowaries, rheas, and kiwis can't fly. Unlike most birds, their flat breastbones lack the keel that anchors the strong pectoral muscles required for flight. Their puny wings can't possibly lift their heavy bodies off the ground. These flightless birds, called ratites, are clearly different from other avian species.

Darwin noticed, and he predicted that ratites were related to each other. His contemporary, Thomas Huxley, found another commonality among them: The arrangement of bones in the roofs of their mouths appeared more reptile-like than that of other birds. At about the same time, another biologist, Richard Owen, assembled the remains of a giant ostrich-like fossil skeleton, the first extinct moa known to the western world. But a pesky detail puzzled Huxley--small, ground-dwelling South American tinamous--didn't seem to fit neatly with the ratites or other birds.

Tinamous fly, albeit reluctantly. And they possess keeled sternums, suggesting that they evolved with flying birds. But their palate bones match the ratites. Where do they belong? Scientists have debated this question for 150 years. Now, a new study analyzing the largest molecular dataset to date, clarifies the tinamous' place on the evolutionary tree and offers clues about the origins of flightlessness. Scientists probed almost 1,500 DNA segments from tinamous, emus, ostriches, the extinct little bush moas, and others, which have generally showed tinamous on the outskirts of the ratite group, relying solely on morphological traits like skeletal details. Other investigations of limited genetic information suggested tinamous were evolutionarily tangled with the flightless birds. "Fundamentally, the recent debate is about molecular data versus morphology," says Allan Baker, lead author of the study. "We can't both be right."

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Study explains why some of our famous flightless birds can't fly

APRIL 5, 2019

by University of Otago

University of Otago researchers in association with colleagues from Harvard University have discovered new evidence of what made some of New Zealand's iconic birds such as the kiwi and extinct moa flightless.

Rather than obvious physical features like small wings, the study identified the molecular roots of the loss of flight seen in a wide variety of these types of birds by precisely analysing DNA. The study, "Convergent Regulatory Evolution and Loss of Flight in Palaeognathous Birds," has been published today in Science.

"This work tells us more about the origins of moa and kiwi. It supports the hypothesis that the ancestral moa flew here, while the ancestral kiwi, which is related to the emu may have walked, or indeed flown from the likes of Australia or Madagascar over the ancient Gondwanan continent," says Dr Paul Gardner, of Otago's Department of Biochemistry. Dr Gardner co-authored the study alongside his former student, Dr Nicole Wheeler.

By comparing the DNA sequences between the different birds, these bioinformaticians have found that it's mostly the regulatory DNA, not the protein-coding DNA that explains the similar loss of flight across the ratite birds. This suggests the change in the regulation of the protein genes, rather than the proteins themselves is what is responsible for the loss-of-flight changes in the birds.

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Giant flightless bird wandered the Arctic 50 million years ago

A single toe bone found on Ellesmere Island in the 1970s is described for the first time

Date: February 12, 2016

Source: University of Colorado at Boulder

It's official: There really was a giant, flightless bird with a head the size of a horse's wandering about in the winter twilight of the high Arctic some 53 million years ago.

The confirmation comes from a new study by researchers from the Chinese Academy of Sciences in Beijing and the University of Colorado Boulder that describes the first and only fossil evidence from the Arctic of a massive bird known as Gastornis. The evidence is a single fossil toe bone of the 6-foot tall, several-hundred-pound bird from Ellesmere Island above the Arctic Circle. The bone is nearly a dead ringer to fossil toe bones from the huge bird discovered in Wyoming and which date to roughly the same time.

The Gastornis (formerly Diatryma) fossil from Ellesmere Island has been discussed by paleontologists since it was collected in the 1970s and appears on a few lists of the prehistoric fauna there, said Professor Thomas Stidham of the Chinese Academy of Sciences in Beijing. But this is the first time the bone has been closely examined and described, he said. Gastornis fossils also have been found in Europe and Asia.

"We knew there were a few bird fossils from up there, but we also knew they were extremely rare," said Eberle, an associate professor in geological sciences who conducts research on fossil mammals, reptiles and fishes. In addition to the Gastornisbone from Ellesmere, another scientist reported seeing a fossil footprint there, probably from a large flightless bird, although its specific location remains unknown, Eberle said.

A paper by Stidham and Eberle appears in the most recent issue of Scientific Reports, an open access, weekly journal from the publishers of Nature.

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Scientists reveal new picture in the evolution of flightless birds

Date:

May 13, 2014

Source:

Molecular Biology and Evolution (Oxford University Press)

Summary:

Because of their far-flung geography and colorful examples including the African ostrich, Australian emu, New Zealand kiwi and long lost giants such as the New Zealand moa, researchers have examined a fascinating part in the story of the avian tree of life: flightless birds, or ratites.

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flightless birds

http://www.weather.com/news/science/nine-amazing-flightless-birds-20130621