[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Non-serpentine lacertids (was RE:WHAT'S GOING ON?)

Mike Keesey wrote:

<<"Lizard" and "snake" are wholly vernacular terms.>>

Eric Lurio wrote: 

<....and so should reptile!!!! If you're going to
stick to the old class system [and why not? it
works!!!!!!], then Squamata(Lizards) and
Serpantes(snakes) are completely valid terms. The fact
that long legless lepidosaurs have evolved several
times [much to the distress of all those
anti-convergance people out there], has nothing to do
with that.>

  To Lurio, and the list in general,

  Even a vernacular term has a definition. What are
the definitions of the terms "snake," "lizard," or
"reptile"? Even "bird" has a definition. Problem is,
they are all vague and general terms; they are used to
simplify intent on what is seen, much as are
scientific names, but less specifically. However, as
Matt Troutman was saying, they were coined and used in
such a manner and time that they reflected types, not
phylogenies. Saying "snake" for a legless repilian
with venom-delivery fangs that moves by contortions of
the vertebrae and attached ribs, is about as general
as you can get, while actually defining the word.
However, nearly all modern phylogenies posit the
origin of snakes from within lizards, unlike the
original "essentialist" and "typological" bases for
Linneans systematics which supported a unique origin
for most groups of lifeforms ... due in great part on
the lack of biological knowledge, genetics, and
understanding of evolutionary mechanics (and theory).

  This shows that some scientific term like Squamata
is not analogous to "lizard," since it includes
"snake" as part of its phylogenetic definition and
content. Your point of multiple occurence of
leglessness occurs in Lepidosauria more than once,
including Serpentes (inclusive of Ophidia, and, I
think, a crown group) and the so-called "blind worms";
amphibians developed legless forms, and many secondary
lacertilian groups did, including xenopeltids, if I'm
not mistaken.

  Now, not to toot my own horn, I have suggested that
we adopt, for sake of clarity of definition when
speaking to one another, that vernacular and
scientific terms be adopted side-by-side, since while
rules will state a term can be scientifically bound to
one definition only (it is a suggested rule, anyway,
no society has adopted it to enforce it ... but I
think the SVP is on that way?), vernacular terms
shift, as part of the evolution of language. Common
usage can change the Oxford Unabridged, which is a
shocking thought. Similarly, I had suggested that even
paraphyletic terms could be used vernacularly, but not
as scientific terminology; though while one could use
"lizards" as all limbed lepidosaurs excluding snakes
(a good definition), saying a scientific term like
Lactertilia to be this usage would be to suggest a
monophyletic arrangement of the taxa involved, and
ultimately not a good practice in the sciences. One
could note that snakes and varanid "lizards" share a
more recent common ancestor than either does with,
say, *Anolis;* and that varanids are "lizards" because
they do not have the serpentine body form, and that
likewise mosasaurs may also therefore be a term to
denote the body type; they are evolutionarily unstable
names because mosasaurs stem from within Varanoidea,
with typical "lizard-like" descendants and ancestors
around the group of aquatic, snake-like forms, and
that snakes in turn descended from them, but are not
themselves mosasauroids. Platynotans (varanoids and
mosasaurs) are a paraphyletic group, by this scenario,
but the name can be used to denote the
monitor/mosasaur stages of the snake development. Note
further that Rieppel et al. have disputed the
mosasaur-origin of snakes, instead using a more
xenopeltid-like group, but the principle is the same.

  Thus "reptile" and Reptilia can be two slightly
different things, and "dinosaur" and Dinosauria be two
slightly, or even more strikingly, four different
things, since there are more than one vulgar
definition to "dinosaur;" but used in the scientific
press, generally dinosaurs are being conceived as
including birds. Some ornithologists (a generality, I
know) have a problem, since there is a rigorous
standing on Linnean-based classification systems, that
would preclude such drastic change in the avian system
to be arrived at from a static, reptilian one. Hence a
push to change the definition of Reptilia so it may
include birds essentially.

  I wish it needn't be done. I can wish, though, that
multiple evolutionary steps didn't mean that there is
now a "Order" ranking to your system, or that if birds
are conceived of a "Class," and both groups of
dinosaurs are "Orders," birds could not, fundamentally
in the classification scheme, evolve from within
dinosaurs. This is my biggest headache when I look at
traditional Linnean classifications ... it does not
seem to willing to take into account that
transformation and convergence are _common_ and often
_implied_ within Nature ... transformation is, in
fact, implied by evolution. I may also be reading my
studies and histories on the development of
classification schemes wrong, and I'm certainly not as
well read in these matters as many of this list's
members, including Brochu and Troutman especially.

  This is why I think Linnean classification is
breaking down ... it does not recognize transformation
in complex systems as a cause of "convergence" nor
does it note transformation may remove an homology
from consideration or perception, despite descent.
Similarly, typology ignores this altogether, and one
stemmed from the other. There doesn't seem to be a
bright way to look at phylogeny without throwing the
book of assumption out the window. Simply, systems
that ignore assumption of relationship or descent, and
deem it neccesary to look at the commonality of things
as basal, or plesiomorphic, rather than unique to
some, and that shared features must pertain to common
origin innately, would be a step above a system that
is static and assumes it is right, without telling you
"why?". Likewise, we are dealing with two systems:
phylogeny, and evolution... the development, and the
relationship between development, and while I tend
towards the first, we all need to understand the
second as well. Together, they make up the bilogical
sciences, and so far, phylogenetic taxonomy (in the
sense of Hennig and Gauthier, and others) has, in my
mind's eyes, acheived the closest rapport and ease
when suggesting possible explanations.

  Considerable more than $0.02,

Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

Do You Yahoo!?
Kick off your party with Yahoo! Invites.