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RE: Swimmin' dinos, fish milk, avian polyphyly (was RE: Sheesh)
The following message was bounced to me because listproc didn't
recognize the address. Tony, please write to me directly if you want
me to do what I can to make sure that doesn't happen to you again...
And I hope you don't mind that I trimmed out some unnecessarily quoted
--- Begin forwarded message
Date: Wed, 25 Oct 2006 16:10:01 +0100
From: Tony Canning <email@example.com>
Subject: RE: Swimmin' dinos, fish milk, avian polyphyly (was RE: Sheesh)
At 8:55 AM -0400 10/25/06, Thomas R. Holtz, Jr. wrote:
> Here are a few thoughts on why the first group of dinosaurs to become
> marine were hesperornithiforms:
> 2) Mechanical constraints. The limbs of most dinosaurs were pretty
> tightly locked into parasagittal motions: great for striding, but not
> terribly good for swimming. Additionally, the major clades had
> mechanisms that tended to tighten up the flexibility of the dorsal
>column (e.g., epaxial ossified tendons or hyposphene-hypantrum
> articulations): again, great for striding, not so good for undulatory
Are there any modern vertebrates that can't swim? I have heard that
camels can't swim, but I think that might be a myth. But then again, I
don't recall ever seeing a swimming camel.
> 3) Physiological constraints. Okay, so this isn't really testable or
> what have you, but just suggesting it...
Not testable, but it may be significant that aquatic forms have evolved
repeatedly in both modern 'typical' endothermic and ectothermic
amniotes; perhaps an intermediate condition such as inertial homeothermy
simply wouldn't work as a starting point in the evolutionary return to
water? Not a strong argument, I know..
> And as for fish milk: a gland that leaks liquid into another liquid
> might not be the best method of delivering nourishment. However, in a
> non-aqueous environment, glands already leaking liquid into air (e.g.,
> sweat glands) might evolve, allowing for exaptation as a source of
> A.P. Hazen: the skin-feeding animal you are likely referring to (the
> one announced earlier this year) was a caecillian (a member of
> Lissamphibia, the modern amphibians), not a fish. However, there might
> well be skin-feeding fish for all I know.
What about discus? See http://www.idiocentrism.com/milk.htm
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