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Re: Yet more reptile stuff (long)



At 11:34 AM 12/18/98 -0600, Chris Campbell wrote:

>> Four or more type of color receptors in the eye, giving greater potential
>> for color acuity.
>
>Is this unique to reptiles?  Seems to be fairly common among mammals as
>well, at least to some extent.

Mammals have only two (most groups) or three (primates) types of color
receptors.  Reptiles (including birds) have more.  They thus have the
potential to divide up the color spectrum MUCH more finally than even we can.

>> A unique system of striated ciliary muscles in the eye that inserts on the
>> lens in an equatorial ring for rapid focusing.
>> A fully developed and highly mobile nictating membrane.
>
>Is this also unique to reptiles?  I know lots of other animals have
>this, particularly sharks; convergence?

Convergence, yes, and I don't know if even sharks have as well developed a
condition as reptiles.

>> Specialized keratinized scales (using different keratins than fish and so
>> forth).
>
>Are the scales in turtles and birds really that comparable?  

Ask Alan Brush.  Those in turtles, lepidosaurs, and crocs, certainly, are
chemically more similar to each other than to those of other vertebrates.

>> Great reduction in the number of glands in their skin.
>
>Compared with what?  Fish?

Yes, and amphibians, and mammals.  We (non-reptilian vertebrates) all have
leaky skins, spewing out slime and pheremones and sweat and other liquids
(pleasant thought...).  Reptiles in general have a greatly reduced number of
glands in the skin.  (They still have a few, but the density is greatly
reduced).

>> Among others: people more familiar with modern reptilian physiology can add
>> these.
>
>I'd like to know these, particularly some which are easily observed.

Then get a book on reptile phyisology.

As for "easily observed": so, again, you want 100-level differences.  Life
isn't always organized that way.
 
>> And anyway, folks who aren't taxonomists tend to think "animals" just means
>> "mammals" anyway.  That doesn't mean that we should stop using Animalia.
>
>What folks are these?  People I've talked to always include birds and
>reptiles and fish in that equation, and usually amphibians as well.They
>don't think of rotifers or worms or even insects, really, but they do
>think of big, non-human, non-plant living stuff.

Then you are lucky.  I teach plenty of people who don't have any background
in biology, and indeed many who don't have a prior interest in natural
history.  This idea is widespread.

If you keep your eyes and ears out, I wouldn't be suprised if you hear the
phrase "animals and birds", for example.

Even here on campus, the College of Agriculture has a Department of Animal
and Avian Sciences.  You can check out the U Maryland website if you want to
verify that.  (And, no, even when folks from Zoology and I complained, they
don't want to change it).

>Nonetheless, you're talking about a history based on that skull
>condition.  I haven't gotten too too much into cladistics, but my
>understanding is that there aren't many other traits associated with
>diapsids (used as part of the definition, anyway) beyond that skull
>condition or membership in a lineage that once had it.

Okay, you admit you haven't read much about cladistics or about the details
of the taxon.  Maybe you might want to wait to do so, before continuing
this?  Diapsids ARE characterized by lots of postcranial features (hindlimbs
longer than the forelimbs being the most "easily observed"): check out most
vert paleo textbooks for others.  Or the U Cal Berkeley website.

>> That's what education, including a forum like this, is about.
>
>It can only go so far, though.  Telling us dinos weren't big, sluggish,
>stupid animals is one thing; movies, books, and popular articles can
>accomplish that.  Telling folks they need to think about reptiles based
>on skeletal features and a host of minor yet significant biological
>traits is a whole different ball of wax.

It just means we have to try harder.  Nobody said it would be easy, or even
reach 100% of the people.  (Of course, the idea that we live on a ball of
rock and metal orbiting the sun is an idea that doesn't seem to have reached
everybody, either... :-S).  but that doesn't mean we shouldn't try.

>> Please don't leave the monotremes out in the cold: they are nursed, but they
>> aren't "born live" as the phrase goes.  (The writer of Science Made Stupid
>> points out that animals whose young are born dead aren't going to leave a
>> lot of descendants...).
>
>That's a derived trait, though.  But, fine; chop off the "bears".

Okay.  (Or, keep it in, and recognize that some groups within the
traditional "Class" Mammalia, such as Theria or Placentalia, actually have
just as much 'meaning' as Mammalia does.)
 
>> >It doesn't tell me what it looks like, how it acts,
>> 
>> And "fish" does?  Please check up on fish diversity some time.
>
>Sure "fish" does.  It tells me the animal has fins of some sort and
>gills.  

Is that all you mean by "acts"?  What about obtaining food, sexual display,
defense, habitiat choice, locomotion, life history changes, etc., etc.?

>> Again, there is a vast world of difference between the common use of the
>> term "animal" and the scientific use of the word "animal".
>
>It's mainly one of scope, not concept.  Scientists include many other
>critters in the term, but they don't use it in a completely different
>fashion, to apply to completely different sets of characteristics.  The
>common and scientific uses of "animal" are not at odds, in my
>experience; the common and cladistic uses of "reptile" are.

The ONLY difference with regards to the common and cladistic use of
"reptile" is the inclusion of birds.  That is it.  Traditional "Linnean" =
turtles, lepidosaurs, crocs.  Cladistics = turtles, lepidosaurs, crocs, birds.

[Also, Linneaus actually included reptiles as a subgroup of Amphibia, with
sharks and sturgeons added in for good measure.]

On the other hand, the ONLY difference with regards to the common and
cladistic use of "animal" is that over 99% of Animalia is excluded from the
common use of "animal" (whether it is "animal" = Tetrapoda, or "animal" =
Mammalia doesn't make much of a difference at this scale).

>> Only if they chose to go no deeper.  
>
>It's not a matter of what they choose.  If you use "reptile" in an
>article they'll think of what they commonly associate with "reptile",
>i.e. cold-blooded, scaly, whatever.  If you use "squamates" (and define
>it, since they won't know what you're talking about at first) or
>"testudines" or "archosaurs and their descendents" the reader has a
>specific idea of what you're talking about and is focusing on the
>animals in questions rather than some vague, baggage-laden term.

Or you explain to them what the new definition means, just as (in a
non-technical article) you often have to explain what a dinosaur is, or a
pterosaur is, or what have you.


>> Then time to play catch up.  Sorry about this, but if you want to get into
>> scientific disucssions, you have to learn how the terms are used, even if
>> they might be the same as commonly used words.  
>
>I know the terms used (or have easy access to glossaries telling me what
>they are).  That's not the issue.  The issue for me is what the term
>means and how it's used by people outside of the realm of cladistics,
>and whether or not it has value for science as a whole given what it
>means to those people.  In my opinion we'd be better off without it.  In
>essence, I've changed my argument on you: I recognize the utility of
>grouping turtles, squamates, and archosaurs together, but dislike the
>use of "reptilia" as a label for that grouping, mostly due to the fact
>that it doesn't mean the same thing to most folks as it does to you. 
>You can say "time to play catch up", but you're gonna have to explain to
>them, in terms they can recognize, why they should bother.

Then I could refer them to the importance of priority in phylogenetic
definitions, or the fact that "Reptilia" has changed its meaning greatly
since the Linnaeus-to-Cope era, or that this is the way the term is used in
the science today.

Once again, the biannual discussion of phylogenetic taxonomy boils down to
the concept "I don't like the way this particular name is used".  Okay, we
hear you.  Many people don't like the fact that _Basilosaurus_ is really a
mammal.  Not liking that isn't reason enough to change it.

>Maybe that
>can be done, maybe it can't, but I haven't seen it done here.

Then perhaps it is time to expand your sources.

>>After all, the physicists use of the common words momentum, mass, weight, 
>>inertia, chaos, acceleration, and so forth are often very different from 
>>the use us ordinary folks use.
>
>Maybe it's just my background in physics (which isn't much, being a
>class shy of a minor as an undergrad), but I've always found that
>momentum, mass, weight, inertia, and acceleration have been used in the
>same ways by both normal folks and physicists.

Lucas's dinosaur textbook, among many others, uses "weight" for "mass";
"momentum" in the public eye almost always has to do with politics (except
sometimes in sports, where it actually is used correctly); "inertia" might
be used correctly when talking about slow or stationary things, but is never
used in a positive sense ("Joe Blow's running towards the goal.  Look at his
inertia: nothing can stop him now!").  You hold a car's accelerator constant
to keep a constant speed.

>Force is mangled a lot,
>but that's just because it means so many different things in so many
>different contexts.  Chaos is used in pretty much the same way, even
>though most folks don't get Chaos Theory.

The original meaning of chaos is the antithesis of cosmos (order), but the
mathematical meaning is orderly, just very sensitive to starting conditions.

>> *BING*!!!  I thought that might be at the heart of this.  "Rank".  Ugh.
>
>Well, that's one way of looking at it.  It's always better to stand out
>than be part of the crowd, IMO.

But never forget, you're always part of the family, no matter how much you
might change.

(Which makes a nice Holiday sentiment, I think!).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661