Some friends of mine in Arizona who have an Emu ranch kindly sent me a nice batch of Emu feathers from various locations on the birds. Immediately I was amazed to see that ALL the feathers are TWINNED! It looks as though two feathers have grown out of a singular sheath (or whatever the right word is).
Amazed, I asked them two questions: (1) Do all Emus have twinned feathers?; and, (2) Are all feathers on all Emus twinned?
The answer was yes, to both questions.
So, I further asked, (3) Are there any other birds than the Emu that have twinned feathers?
They said that so far as they know, no other bird has twinned feathers, and that all emu ranchers they know have said that Emus are unique in this.
Well, of course I'm not sure of the reliability of that last answer, because I am not convinced that Emu ranchers are necessarily experts concerning the feathers of other birds. But, if twinned feathers are in fact unique to Emus (or to just two or a few species of bird), I am wondering whether feather twinning should be (or is) a considered factor in classification, because of its uniqueness or rarity.
Also, should one consider the possibility that feather twinning may be an adaptation to some factor in the Emu's environment and/or lifestyle? If so, WHAT? From an evolutionary standpoint, how did feather twinning come about, and in what ways might it be advantageous?
Have we an expert among us that can elucidate this quandary?
The same Arizona friends sent me some superb photos of fresh Emu tracks. It was interesting to observe that Emu tracks are remarkably identical -- in both shape and size -- to a certain type of dinosaur tracks from the Early Cretaceous of Maryland.
I told this to one of the Arizona Emu ranchers, and he responded, "No surprise. Emus ARE dinosaurs! All the publicity in recent years declaring birds to be dinosaur descendants is no news to me and a lot of Emu people. And dinosaurs -- at least the Emu kind -- have a powerful weapon in their legs and feet! Heck, an Emu can disembowel you with one strategically placed kick!"
So now I wonder whether some Mesozoic non-avian, avian, or maybe secondarily flightless dinosaurs might have had twinned feathers, 'proto-feathers', integumentary fibers, or whatever.
Any clarification or help would be appreciated.
Thanks, Ray Stanford