Re: Two more gaps in the fossil record
Sat, 16 Oct 1999 20:03:53 +0000

At 09:05 AM 10/17/1999 +1000, Jonathan Clarke wrote:
>Hi Glenn
>A terminology question here. What is meant by "hollow bones"? Many bones
have a
>central cavity, filled in life by marrow. All bones also are porous. What
>distinguishes the follow bones of birds from these? I recall reading
>that the hollowed bones of birds contain air sacs. This was supposedly to
>high respiration rates. Is this correct for all hollow bones in birds?
If true,
>is a different adaptation to aerial life than simply reduction in weight, a
>feature found in other flying vertebrates like bats and pterosaurs. Did
>taxa also have how bones in the same sense as birds?

My understanding is that the bones of birds are hollow and connected with
the respiratory system. Ostriches use these airsacs to help cool themselves

But of course it does reduce weight and help the flight characteristics of
the bird. Bats and pterosaurs do not have hollow bones to the best of my

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