Re: off-topic marine mammals

["T. Michael Keesey" <keesey@gmail.com>]

On Fri, May 2, 2008 at 9:59 AM,  <hammeris1@bellsouth.net> wrote:
>
> I think that's a good approach - definitely an ancestor,

(Well, not "ancestor" -- as discussed on another thread, we pretty
much can never prove that a given fossil organism is ancestral to any
living organisms. However, change that to "ancestor model" or
"potential ancestor" and you've got something.)

> close-kin,

(Also good.)

> but a true "whale" begins when the creature becomes fully marine.

Actually, this brings up a good point. Words like "whale", "horse",
and "fowl" don't actually refer to any apomorphies. They're discrete
morphemes which can't be parsed any further--they just mean what they
mean. For common day-to-day usage, this is fine, but it creates a
problem when looking at the related stem groups. (The more-or-less
corresponding formal names _Cetacea_, _Equus_, and _Aves_ are similar
in this regard.)

Is a marine lifestyle what makes a whale a whale? What about river
dolphins? Is it just an aquatic lifestyle? Or is it the loss of
hindlimbs? The development of flukes? The dorsal fin? The blowhole?

Is it the loss of all digits except one what makes a horse a horse?The
switch to a grass-based diet? (Actually, since when do people consider
zebras and donkeys horses? Isn't it just _Equus caballus_?)

Do feathers make the fowl? Feathered wings? Feathered wings used for
powered flight? Pygostyles? Keeled sterna? Beaks?

Exploring this sort of semantic issue seems to me like a good way to
introduce people to the concepts of crown groups, stem groups, total
groups, and apomorphy-based clades, and especially the corresponding
concepts of survival, extinction, cladogenesis, and character
acquisition.
-- 
T. Michael Keesey
Director of Technology
Exopolis, Inc.
2894 Rowena Avenue Ste. B
Los Angeles, California 90039
http://exopolis.com/
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