AP BIOLOGY

Detailed explanation-1: -The evolutionary tree places Lithornis as a common ancestor of ratites. It had functional wings so could have flown overseas from the North to the Southern Hemisphere where it eventually evolved into ostriches and emus, the authors suggest.

Detailed explanation-2: -Rather than being flightless, their ancestor was a partridge-like bird that could travel by air. Between 65 and 50 million years ago, early ratites flew across much of the world, finding new homes where they could settle.

Detailed explanation-3: -Ostriches and their flightless relatives are found across the globe not because continental drift forced them apart, but rather because the ancestors of these birds spread across the world through flight, and only later became flightless, researchers say.

Detailed explanation-4: -Newly studied fossils suggest that the ancestors of ostriches are instead among a group of North American and European birds, the ‘Lithornis-cohort’, that had the potential of flight and from which the kiwis may have arisen separately.