LiveScience has a story that looks a paper about flightless birds and how they may have dispersed across multiple continents. The paper “Quantitative analysis of stem-palaeognath flight capabilities sheds light on ratite dispersal and flight loss” was published in the journal Biology Letters.

Ostriches, emus, rheas and other large, flightless birds  (paleognaths) are closely related, but how they ended up in widely separated places was not understood. One hypothesis was they spread out on the super continent of Pangaea. Unfortunately, Pangaea broke up some 195 million years ago, which disagreed with genetic studies that found the last common ancestor of these birds lived about 79.6 million years ago. The authors analyzed a specimen of Lithornis promiscuous and compared the shape of its sternum, or breastbone, with modern birds that fly long distances. The shape indicated it could have handled a range flapping flight styles that would have enabled long flights.

To work out what happened, Klara Widrig, a vertebrate zoologist at the Smithsonian National Museum of Natural History in Washington, D.C., and her colleagues analyzed a specimen of the ancient paleognath Lithornis promiscuous. Although it lived around 59 to 56 million years ago, it is the oldest fossil palaeognath found in such pristine condition.

“We can’t tell for sure if Lithornis was the direct ancestor of our living paleognaths — it is entirely possible that the true ancestor is yet to be discovered — but it represents our best guess as to what the ancestor would have looked like,” Widrig told Live Science.

Previous investigation of preserved feathers of a slightly more distantly related lithornithid called Calciavis grandei indicated that it could have flown, but it wasn’t clear how far. No one had done a quantitative analysis of the shape of lithornithid bones to try to answer that question.
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“We found that the shape of the breastbone was really similar to that of living birds that are capable of flying very long distances across oceans, like great egrets and herons,” Widrig said.

“This is very interesting because the great egret is a cosmopolitan species in that it travels from continent to continent,” said Peter Hosner, curator of birds at the Natural History Museum of Denmark, who wasn’t involved in the work.