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Re: Yet more reptile stuff (long)
Thomas R. Holtz, Jr. wrote:
> 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.
Excellent! Glad to see they finally got around to that. :-)
> >> 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
I've always thought this was a great adaptation. Fish, amphibians, and
mammals are all far too slimy for their own good, IMO; part of the
coolness of the whole diapsid line is their general dryness.
> >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.
I dunno. I think it's more a matter of usage than perception. Sure,
people refer to mammals as animals and everything else specifically
(fish, birds, reptiles, whatever), but I'm not sure that means they
don't think of the other critters as animals.
> 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).
Well, how many ornithologists work in said department? If a good chunk
of the department is into birds there's your answer right there. It
isn't necessarily ignorance so much as the self-importance of bird
> >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.
Of course there are other details involved, just as with any taxon. But
the main feature, the keystone, is the skull. When you look up a
comparison of anapsids, synapsids and diapsids, even in something like
Farlowe's and Brett-Surman's book, the main feature discussed is skull
morphology. That's the feature that counts, and the one the names refer
> >> 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.
We should try, but there are better things to expend our energy on than
redefining people's definitions of "reptilia". Personally, I'd much
rather redefine the ways in which they view the animals, recognizing
them for the cool animals they are instead of slimy, scaly creatures who
are inferior to mammals.
> >> >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
> Is that all you mean by "acts"? What about obtaining food, sexual display,
> defense, habitiat choice, locomotion, life history changes, etc., etc.?
Those things aren't important in a single word. The word just has to
tell me something easily pinned on the animal (again, with common
definitions such as these). "Fish" tells me plenty about fish. It
doesn't have to tell me about locomotion or life history strategies to
> >> 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.
No, that is *not* it. You're talking about membership, I'm talking
about implications of the word, how it's used, and what it means. These
things are completely different, even diametrically opposed in some
cases, in the two uses.
> 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 you buy into the notion that common usage of animal excluded
birds, fish, and herps. I don't buy it. It doesn't typically include
invertebrates of any sort, so your percentage might not be too far off,
but these exclusions are generally made even by folks who know better
simply out of convenience.
> >> 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.
And it's very easy to explain what a dinosaur is, or a pterosaur, or
what have you. Defining "reptile" as you mean it in this way is not
easy at all, at least not in a relevant way.
> 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.
And they're still gonna want to know, in terms they can understand, why
this change occurred.
> 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.
You've changed the membership and the characteristics used to define an
animal as a member of the group. In other words, basically everything
about it. That's plenty of reason to change it.
> >>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";
This confusion is actually very understandable, as metric scales give
readings in terms of mass instead of weight. But your point on this is
> "momentum" in the public eye almost always has to do with politics (except
> sometimes in sports, where it actually is used correctly);
That may be, but that doesn't mean it's used incorrectly, or that people
think of it differently than they do in the physical sense.
>"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!").
Say what? I've never, ever heard inertia used like this. I typically
hear it used in more abstract terms, sometime in a political sense, but
always in keeping with its scientific usage.
>You hold a car's accelerator constant to keep a constant speed.
Well, yeah, you do, because due to the effects of drag and friction you
have to continually accelerate to maintain a constant velocity. The
car's accelerator is still used to accelerate to a given velocity, so
the term is generally used correctly here.
> >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.
True enough. Blame the mathematicians. We all know math is evil
> >> *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.
Well, yes, but we're talking class here. The turtles gotta be wondering
if the teacher will ever let them out!
> (Which makes a nice Holiday sentiment, I think!).
It does, true.