Like the ostrich, rhea, cassowary, emu, kiwi and extinct moa, Mullerornis and Aepyornis were ratites; they could not fly, and their breast bones had no keel.
 Because Madagascar and Africa separated before the ratite lineage arose, Aepyornis has been thought to have dispersed and become flightless and gigantic in situ.

More recently, it has been deduced from DNA sequence comparisons that the closest living relatives of elephant birds are New Zealand kiwi, though they are not particularly closely related, being estimated to have diverged from each other 54 million years ago.
Elephant birds are actually part of the mid-Cenozoic Australian ratite radiation; their ancestors flew across the Indian Ocean well after Gondwana broke apart.
The existence of possible flying palaeognaths in the Miocene such as Proapteryx further supports the view that ratites did not diversify in response to vicariance.
Gondwana broke apart in the Cretaceous and their phylogenetic tree does not match the process of continental drift.
Madagascar has a notoriously poor Cenozoic terrestrial fossil record, with essentially no fossils between the end of the Cretaceous (Maevarano Formation) and the Late Pleistocene.
Molecular clock estimates from complete mitochondrial genomes obtained from Aepyornis eggshells suggest that Aepyornis and Mullerornis diverged from each other during the mid Oligocene around 27 million years ago, suggesting elephant birds must have been present on Madagascar before this time.

Claims of findings of "aepyornithid" egg remains on the eastern Canary Islands, if valid, would represent a major biogeographical enigma.
These islands are not thought to have been connected to mainland Africa when elephant birds were alive.
There is no indication that elephant birds evolved outside Madagascar, and today, the Canary Island eggshells are considered to belong to extinct North African birds that may not have been ratites (possibly Eremopezus/Psammornis, or even Pelagornithidae, prehistoric seabirds of immense size).
Various "aepyornithid-like" eggs and bones occur in Paleogene and Miocene deposits in Africa and Europe.

Two whole eggs have been found in dune deposits in southern Western Australia, one in the 1930s (the Scott River egg) and one in 1992 (the Cervantes egg); both have been identified as Aepyornis maximus rather than Genyornis.
It is hypothesized that the eggs floated from Madagascar to Australia on the Antarctic Circumpolar Current.
Evidence supporting this is the finding of two fresh penguin eggs that washed ashore on Western Australia but originated in the Kerguelen Islands, and an ostrich egg found floating in the Timor Sea in the early 1990s.
Like the ostrich, rhea, cassowary, emu, kiwi and extinct moa, Mullerornis and Aepyornis were ratites; they could not fly, and their breast bones had no keel.  Because Madagascar and Africa separated before the ratite lineage arose, Aepyornis has been thought to have dispersed and become flightless and gigantic in situ.
More recently, it has been deduced from DNA sequence comparisons that the closest living relatives of elephant birds are New Zealand kiwi, though they are not particularly closely related, being estimated to have diverged from each other 54 million years ago. Elephant birds are actually part of the mid-Cenozoic Australian ratite radiation; their ancestors flew across the Indian Ocean well after Gondwana broke apart. The existence of possible flying palaeognaths in the Miocene such as Proapteryx further supports the view that ratites did not diversify in response to vicariance. Gondwana broke apart in the Cretaceous and their phylogenetic tree does not match the process of continental drift. Madagascar has a notoriously poor Cenozoic terrestrial fossil record, with essentially no fossils between the end of the Cretaceous (Maevarano Formation) and the Late Pleistocene. Molecular clock estimates from complete mitochondrial genomes obtained from Aepyornis eggshells suggest that Aepyornis and Mullerornis diverged from each other during the mid Oligocene around 27 million years ago, suggesting elephant birds must have been present on Madagascar before this time.
Claims of findings of "aepyornithid" egg remains on the eastern Canary Islands, if valid, would represent a major biogeographical enigma. These islands are not thought to have been connected to mainland Africa when elephant birds were alive. There is no indication that elephant birds evolved outside Madagascar, and today, the Canary Island eggshells are considered to belong to extinct North African birds that may not have been ratites (possibly Eremopezus/Psammornis, or even Pelagornithidae, prehistoric seabirds of immense size). Various "aepyornithid-like" eggs and bones occur in Paleogene and Miocene deposits in Africa and Europe.
Two whole eggs have been found in dune deposits in southern Western Australia, one in the 1930s (the Scott River egg) and one in 1992 (the Cervantes egg); both have been identified as Aepyornis maximus rather than Genyornis. It is hypothesized that the eggs floated from Madagascar to Australia on the Antarctic Circumpolar Current. Evidence supporting this is the finding of two fresh penguin eggs that washed ashore on Western Australia but originated in the Kerguelen Islands, and an ostrich egg found floating in the Timor Sea in the early 1990s.
Elephant bird