Although I’ve not done a scientific survey, most dogs have a little double flap, or double layer of skin, on one side of their ear, the side closer to the ground.
What’s the purpose of that little flap? just a quirk of evolution?
I think I know the bit you’re talking about. I don’t know much about dog ears, but it might be involved in locating the direction of sounds.
Ear shape modifies the sound you hear according to its direction, as it reflects off the convolutions. Take a look at http://www.sfu.ca/sca/Manuals/ZAAPf/b/binaural_local.html for a brief description, or http://www.binaural.com/binfaq.html for more than you wanted to know about synthesizing sound-position info.
Or maybe it is just a quirk.
In this thread http://boards.straightdope.com/sdmb/showthread.php?threadid=30964 I said
bibliophage, that’s what I meant - thanks. As you say, if the anatomy profs don’t know…
rjk, I’m not sure that it would affect the dog’s ability to hear, because it’s found on dogs with pointy-up ears (like in the illustration bibliophage posted), and also in floppy hang-down ears (like beagles and bassets). Although it’s located in the same anatomical region of the ear in both cases, I would think that the different physical location would mean that it would not have the same effect on the dog’s ability to hear.
If the anatomy profs don’t know, you can’t look it up, so you have to figure it out for yourself.
Cats and dogs apparently diverged from their common ancestor (Miacis) 30 or 40 million years ago. That seems like a very long time for such a complex structure to hang around if it were just a quirk of evolution.
If you grab a handy cat, or dog ?, and pull the back of their ear directly away from the head, you’ll see that the structure stretches like a spring, (or a folded piece of paper when pulled). The stress exerted by pulling on the ear also looks to be more spread out with the flap thing, than it would be if the ear were more simply constructed. So maybe the flap helps prevent torn ears during fights etc. ?
For a cat ancestral tree see: http://dspace.dial.pipex.com/agarman/bco/prehistoric.htm
A Google search on “Miacis”, “prehistoric cat” or “prehistoric dog” turns up scads of interesting stuff.
I asked this question 24 years ago and got a “no-one seems to know” answer, as set out above.
Today, 24 years on, through the miracle of Wikipedia, I discovered an article on this very topic!
The answer?
“No-one seems to know”.
But, at least there’s a name for it!
I give you:
But why? Why “Henry’s pocket”?
Answer:
“No-one seems to know.”
But at least we now know that it’s not restricted to dogs and cats.
Bats have Henry’s pockets, too!
Check back in, in 2049, for the next update!
It’s the perfect size on most dogs to insert your finger and annoy your dog. Form follows function!
I had heard it is the canine variation of the human earlobe. Which, if true, doesn’t answer your question.