Ancestors of Ostriches & Emus Were Once Long-Distance Fliers

New fossil evidence suggests the predecessors of today’s flightless giants—ostriches, emus, cassowaries, rheas, and kiwis—were once capable of sustained flights across vast distances.

Researchers examined a ~56-million-year-old fossil of a bird closely related to palaeognaths (the group including ratites and tinamous). The bone morphology, especially of the sternum, strongly resembles that of known long-distance flying birds such as herons and storks, indicating that these ancestors retained flight ability.

This finding challenges older models that explained the wide geographical spread of ratites by continental drift alone. If their ancestors could fly, they likely dispersed across oceans and land barriers long after the breakup of Gondwana. Over time and in predator-safe environments, multiple ratite lineages independently lost flight and evolved into giant terrestrial species. Genetic data also support this view: molecular clocks place the split of major ratite lineages well after continental separation, making flighted dispersal a more plausible path.

The transition to flightlessness, the authors argue, may have been driven by reduced predation pressure and the high energy costs of flight. In stable ecosystems without major aerial predators, evolving into more efficient runners or large ground dwellers would be an easier path.

Today’s tinamous, small ground birds still capable of short bursts of flight, may echo that ancient versatility. This study reframes how scientists understand the evolutionary journeys of flightless birds, showing that their grounded life was a derived trait, not an ancestral disadvantage.

Key Takeaways 

1. Flighted beginnings: The ancestors of ostriches and emus likely retained strong flying ability, based on fossil sternum features.

2. Dispersal via air, not land: These birds may have spread to distant continents by flight, not solely through plate tectonics.

3. Independent loss of flight: Multiple ratite lineages arrived airborne, then evolved flightlessness separately under ecological conditions.

Adapted From:

https://theconversation.com/the-ancestors-of-ostriches-and-emus-were-long-distance-fliers-heres-how-we-worked-this-out-266081