Re: Most popular/common dinosaur misconceptions

["Jaime A. Headden" <qilongia@yahoo.com>]

Jura (pristichampsus@yahoo.com) wrote:

<Calling a bird a dinosaur is a completely different thing from calling a bat a
mammal. It is more akin to calling a mammal a therapsid, or a snake a lizard.>

  In this, the contra-comparisons are false. A lizard represents an entirely
different entity than a snake, often entailing only the sister-group of all
snakes including all other living lacertilians. That snakes are members of
Lacertilia, yes, as mammals are members of Therapsida, and birds are members of
Dinosauria. It used to be that bats were NOT considered members of Mammalia,
but were included with birds by Linnaeus. 

<It's attempting to lump two large and diverse groups (both of which were
originally named based on morphological criteria) into one, strictly for the
sake of monophyly. This is confusing and disconcerting because it assumes no
real change occured between the groups and invites the use of superfluous (and
frankly unwelcome) qualifying terms to indicate a separation that was already
assumed before the lumping occured.>

  The only change that occured "between" the two groups is equivalent to the
change that occurs within them at any particular given split. Say, Galliformes
from Galloanseres. Cetacea from Mammalia involves some massive changes, but it
is actually rather ridiculous that we not call whales mammals because they
don't look like other mammals. Cetacea and Mammalia were both also founded
originally on morphological grounds. I see the typological in the above, and
the desire to make conceptual concepts "real" by making them equivalent,
perhaps a validation of a childhood recognition of the Classes Aves and
Reptilia, and the need to anchor this in the ever-changing world. Monophyly
seems the logical means to organize descent, since it best captures containing
groups THROUGH it, yet the argument for separating groups because of perceived
differences is typological, and organizes no real evolutionary information in
its structure. This seems but to pander to an illogical, old system.

<Of course I'm referring to the term: "non-avian dinosaur" to indicate what was
originally just called a dinosaur.>

  And so phraseology can change as we start to incorporate descendants into
wholes? I see no problem with this, actually. I know that this term only seeks
to look at a paraphyletic assemblage, and certainly needs no nomenclature to
fuddle or try to compete for our attention ... and one doesn't need to use it,
if one disagrees with it, but it seems more logical than to coin terms or
pander to polyphyly or paraphyly in order to avoid it.

<I can think of dozens of papers that have come out over the past decade where
the term "non-avian dinosaur" could be replaced simply with the term "dinosaur"
without changing the paper's meaning one bit.>

  Escept that they are usually attempting to exclude the modern avians who have
acheived a variety of niches, ecomorphologies, metabolic changes, and
morphologic variations not otherwise available, especially since the average
avian is about 1% the size of the average non-avian among most of Archosauria.
They can as easily use non-avian archosaur and acheive similar results, but
non-avian dinosaur restricts the field, non-avian theropod and non-avian
coelurosaur further.

  Take us to your non-gavialid crocodylians, your non-testudinid chelonians,
your non-equid perissodactyls....

  Separate an ecomorphology or a group to qualify that group's useage, perhaps.

<Theoretically the term non-mammalian therapsid, or non-ophidian lacertillian
might also crop up now and again, but I've yet to see it (admittedly the
lacertillian one doesn't show up mostly due to the weirdness of lacertillian
phylogeny). This particular thorny part of taxonomy seems to be limited to
dinosaur paleontology (though Eric Pianka & Laurie Vitt are guilty of throwing
out an occasional "snakes are just lizards").>

  Good for Pianka and Vitt. Because they are. Speaking evolutionarily, anyway.
Speaking in different langauges, now.... However, dinosaurs and their allies
became the proving ground because this particular part of the animal tree was
the specialty of many of the first-rate anatomists who dug into the
"terminology of terminology" region of systematics. Just because it's not used
as much in other groups, which can often be lain at the feet of a rejection of
cladistics because the people who work those groups mistakenly equate
phylogenetic taxonomy and systematics with cladists, and thus reject the terms,
and favor more illogical Linnaeism.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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