Captured at newsgroup alt.animals.dolphins
I am trying to find information about dolphin and other aquatic mammal evolution. The question is how they got their blowholes where they are. I believe that the blowhole is actually a fusion of the two nostrils that has moved back over time. But, isn’t the hole behind the brain, and if so, how did it go around the brain?
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and got several great responses. Thanks, Peter and George. I also got the following from Stacy Braslau-Schneck and thought that it would be good for the group as well:
The skull got its current shape through a process called “telescoping,” named after the old-fashioned brass telescopes that could be pulled out or collapsed. The upper part of the dolphin’s rostrum or muzzle area is roughly the equivalent to the upper lip area on our skulls; this bone has been enormously lengthened to allow the nostril openings to be as high on the head as possible. (The rest of the skull got changed in interesting ways; it’s kind of tilted and compressed in various ways. This is partially due to this telescoping and partially due to other factors like the need to hear sound through water with a system that originally evolved to hear sound through air.)
Hope this helps!
