As I discussed in my previous two posts, paleognaths are a group of birds that includes large-bodied flightless species such as ostriches, emus, cassowaries, and the extinct moas and elephant birds, as well as the small flightless kiwi and the quail-like tinamous.
Molecular phylogenetics suggests that these predominantly flightless birds descended from birds that were capable of flying. One group of fossil paleognaths, known as lithornithids, provides strong evidence of this flying ancestry.
Pseudocrypturus cercanaxius, an example of a lithornithid
Lithornithids are the earliest known fossil paleognaths, possessing the more reptilian-like jaw characteristic of the group. They have been found in rocks dating from 61.7 to 40.4 million years ago in Germany and Wyoming . Their sterna, or breast bones, were strongly keeled, which allowed for the attachment of muscles used for flight.
The red arrow in the image on the left indicates the keeled sternum of a flying bird. In the image on the right, you can see the smooth, non-keeled sternum of the flightless emu.
Since the earliest known fossil paleognaths were capable of flight, it tells the same story as molecular phylogenetics, which provides evidence of flightless paleognaths descending from flighted species. As these species adapted for flightlessness, they appear to have lost the keel in their sternum since they no longer need strong breast muscles for flight.
Questions for Creationists
Where did the lithornithids go? If they were capable of flying, shouldn’t they have survived Noah’s flood? Is it a coincidence that the earliest fossil paleognaths were probably capable of flight and molecular phylogenetics suggests that flightless paleognaths descended from flighted species?