Re: BAD vs. BADD (was: Re: Most popular/common dinosaur misconceptions)

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

Jura (pristichampsus@yahoo.com) wrote:

<A couple others on the list gave mention to this too. I feel that this is more
of a cop out than it is an answer. Both lizards and snakes are members of the
> group (order) Squamata, but it's referring to the names of the subgroup (the
suborder) that I'm questioning. No one says non-ophidian lacertilian
(non-serpentean saurian, or any mix inbetween). Yes one could say non-ophidian
squamate, but it's much easier to just say saurian, or lacertilian. In both
such cases, the exact meaning is made apparent without the loss of the
knowledge that snakes evolved from lizards.>

  Yet Sauria itself is paraphyletic with respect to Serpentes or Orphidia
(whichever you prefer) as long as you exclude them as members of Sauria, or if
you include the ansectral lineages of Serpentes but within Sauria. There is no
scientific term for a bulk of lizards without invoking some group that is
ancestral to snakes, except for the well-known subgroups of Iguania,
Amphisbaenia, etc., none of which are known to derive snakes themselves.

<If anything, you and others raise an interesting point. Why not use/create a
higher "level" grouping that is understood to contain dinosaurs and birds?
Something like "Dinoaves," but preferably more original (besides I think GSP
already used that term).>

  Well, Avemetatarsalia, Dinosauriformes, Dinosauromorpha, the total clade of
*Aves* (in some cases, the pan-clade of *Aves* of "pan-*Aves*" or
pan(*Aves*))....

<Well, for one, birds locomote in a manner completely different from those of
dinosaurs (classic dinosaurs). I'm not talking about flying either. No dinosaur
has been shown to be a tibia based walker. There was an argument in favour of
_Caudipteryx_ doing that (at least a little bit), but this seems to have been
based on bad data. Dinosaurs probably didn't see like birds either; with
relatively fixed eyes that require head bobbing in order to walk effectively.>

  Well, avian crouch walking is NOT a problem, since it's an apomorphy for a
select group. It is virtually meaningless to divide off a group because the
mebers of that group share a feature, since all that does is define the
ingroup.

  *Caudipteryx*'s ability to crouch-walk is not a problem, as the bad data
Jason notes was based on the study with Jones and Farlow on bird leg length
ratios, which had some flawed data in it, but still proposed crouch-walking.
John Hutchinson has also favored crouch-walking as a possible solution to
locomotion difficulties in *Tyrannosaurus rex*, and this model might be
exaptable onto other dinosaurs.

  But as long as we would be discussing differential locomotory modes, consider
also the possibly primate-style system that *Microraptor* might employ,
four-legged clamboring, and then four-legged gliding and maybe even four-winged
flapping (a la Greg Paul's paradigm). This does not earn *Microraptor* it's own
Class, however.

<In all honesty the only grey area that I've ever seen with birds and dinosaurs
involves a small set of maniraptors and very early, (archaeopterigiformes and
such) birds.>

  Which is probably due to the thoroughness with with the holes in evolutionary
lineages are being filled, and this mostly due to phylogenetics resolving
relationships among these organisms. Basal birds are extremely well populated
(and likely to collapse a tad only due to oversplitting taxa).

  Yet such grey areas exist all through known groups of organisms: Cetacea has
as its grey area the ambulocetes and the pakicetes part of the "archaeocete"
transition, where walking was still a primary means of locomotion. The skulls
show similarities to many other fully terrestrial carnivores, provoking
allusions to mesonychians at the base of artiodactyls, while the ankle (and
molecules) seems to point specifically at hippos. This "grey" area is also very
well known. The lizard--serpent transition is also very well studied and very
much a gradational cline at this point, as in the
rhiphistidian--"stem-tetrapod"--"amphibian" transition. These "transitions" are
simply due to using vernacular as a consequence of labelling groups, however
false and artificial they are, for collections of animals that form a nearly
unbroken line. [More on that below.]

  But something that is not really well-brought up is that the transition from
archosaurian stock INTO Dinosauria is not that well understood, and this is not
the fault of the phylogenies to explain but because the early, middle, and late
Triassic beds of note known do not preserve this material well enough to
clarify issues, or bring us to the fossils that might have survived. No one
argues, however, that dinosaurs are not archosaurs, and are not the sister
taxon to crocodilians (just as genetically, that's the place birds go).

<If this is true, then why do I see Jaime and others arguing that there is no
gap?>

  The gap we speak of is different than the gap you speak of. For me, the "gap"
is between species through speciation. Life, as I see it (and I've had help) is
not a tree but a web at low resolution, and only at low, VERY low resolution
does it look like a tree, where the divisions are simply an artifact of
non-interaction between genetic lineages. Genetically, we would term this
isolation, and the appearance of speciation. But within that web, there is no
speciation, no "breaks", and no labels. Life's pattern, as it might become
obvious (if true) is a matter of resolution.
 
<Quick aside: it should be pointed out that Lamarck did view the evolution of
life as a tree, and not a straight line ladder arrangement. This occurred later
in his life, but was still published. He really wasn't as backwater as he is so
often portrayed.>

  Indeed, it is good to point this out since Lamarck was one of the pioneers of
evolution, not "that other stuff". The golden ladder was proposed after
Lamarck, but it used Lamarck's theories as a ground breaker to propose
organization, and this led to the Ladder itself, which just found its niche
being exploited by certain evolution-naysayers. The term evolution had been
used at that point and became exapted for use on the ladder as a progression
toward the ultimate creature (us, something Lamarck also believed in, though if
I recall correctly Lamarck thought that all life would eventually develop
toward this "human" state on their own, and each in their own way, but we
represented the epitome). The naysayers, however, use the progression and
evolution to apply humans as the ultimate and unreachable, since it could only
happen one way, and only once (and they had a book to prove it). [If I say
anymore, I could find myself banned.]

<I've only seen them go up to superfamily (Iguania, Scleroglossa), but I'm not
sure if they've ever gone further. I know they still accept order Squamatas, if
that counts.>

  Those names are not superfamilies, though, they are clade names, or at the
least suborders. Superfamilies take the form [name]-oidea as a consequence of
the ICZN.

<I've seen you get pretty heated over this in later posts. You seem very
insistent on stating that words like "lizard" and "fish" hold no sway in this
debate (and that they basically mean what they were historically assumed to
mean).> ... <Yet, and this part bugs me, everytime a person on this list says
that birds are dinosaurs (or just invokes the acronym BAD), I see quiet.>

  I would tend to think that the use of the terms as used there is pointing out
the vernacular, rather than just casually adopting it. Then again, "bird" has
never been treated as a paraphyletic group, "fish" and "lizard" have. Using
"fish" and "lizard" to represent evolutionary entities, but assume they are
equivalent to clade groups gives people the impression they are equivalent as
clade groups to monophyletic taxa like Tetrapoda, Serpentes, or Aves.

<Even if the fossil record was perfect, I find it hard to believe that
dinosaurs surpassed this number at any one point in time (the limitations of
being big).>

  Why? I find it not at all difficult to not only be able to completely
discount the potential evolutionary number of organisms without capability of
genetic interchange or breeding (aka, "species") in birds, but also to
potentially argue that any extinct group could have been as numerous, because
of the nature of the fossil record. Additionally, living organisms like all of
birds are rampantly oversplit, as are living snakes and living "non-ophidian
squamates". Reduction to the BSC would result in so many and far fewer species
that we would be much more hard-pressed to find any true distinction between
extinct and living dinosaurs in species numbers. Especially given that all of
these Mesozoic dinosaurs we love so dearly are distinguished solely on explicit
morphologic grounds. Such grounds would collapse genera and families of birds
into single a single entity, something I beleive Mike Taylor considered when he
composed his paper trying to find an equitable way to assess diversity, ending
at having to use the accepted nomenclature to distinguish particular types of
organisms. We don't have a way to measure morphologic change across organisms
to date -- save for computer-based programs -- or to map this reliably to
genes, which is really meaningless anyway since we don't know what genetic or
morphologic change really MEANS with relation only among other genotypes other
than at a certain difference, a genome ceases to be capable of pairing with
another, and a particular amount of morphology might be equivalent to this
distinction, thus "species."

<I admit that cetaceans have done some serious morphological upheavals to get
to where they are. They are also the only mammal group to be comprised solely
of giants (even dolphins are big).>

  Only if you're using yourself as a metric (rather anthropocentric!) or maybe
even living terrestrial biomass. To a cetacean, a porpoise is pretty damn
small, compared to the largest, but in all, most cetaceans (based on species
diversity and biomass) are 10 foot or less, and weight in the ton or less
category. There's something about living in an ocean that requires a particular
mass to be neccessary. So all in all, I'd say cetaceans are small ... though
they include some of the biggest mammals ever to live.

<I'd hesitate from separating them as a class just because they still retain
many of the key features that unite mammals (the inner ear bones, suckling,
etc).>

  They lack hair, another feature people should think are neccessary for being
a mammal. Even humans haven't lost that.

<They also hold relatively limited niches, and diversity. Admittedly though,
the latter is probably that limitation of being big, thing again.>

  This sounds like begging the differences: Whales can be mammals, 'cause they
still have the mammal definitions (morphologies not every agrees we should
use), but birds can't be dinosaurs because .... they share the morphologic
features that unite dinosaurs, but have their own differences that make them
"special", such as the aforementioned unique mode of walking?

<The others don't appear to be as derived away from Mammalia in general, as
cetaceans (even bats still retain fur, the inner ear bones, and still suckle
their young).>

  Now, what if I were to point at exceptions to these rules: hairlessness,
reduction of the ear bones (some fuse two of the bones), and absence of
suckling. Would these still qualify as mammals? It used to be live-bearing was
a requirement of mammals, too, but that seems to be left out of the classic
list. Now, morphologic analysis of some jaw bones is indicating that a fully
mammal jaw can occur WITHOUT all ear bones. Monotremes do not suckle, per se,
and some mammals fuse their inner ear bones (not all of them), and there are
plenty of completely bald mammals.

  From this, I would argue ... birds have scales ... birds can enter into a
state of torpidity meaning they are not fully warmblooded ... and birds lay
hardshelled eggs (some are even temperature dependant for sex determination,
such as megapodes). What DOESN'T make birds reptiles? Using the classic sense
of the terminology, of course. Or ... why isn't *Ichthyostega* a fish?

  These are ridiculous questions, of course. We all known *Ichthyostega* is a
lungfish ... or a coelacanth ... or an amphibian. Oh, maybe it IS a fish....

<Snakes don't warrant a separate status just because they are limbless.>

  But it helps.

<It's the huge changes to their skull that matters more.>

  This, also helps, but it's hardly true -- I should think -- that is matters
more. They also have similar ribs on ALL vertebrae, virtually no distinction
between caudal, sacral, dorsal, and cervical series (save for the atlas and
axis), and a very unique form of movement other so-called "legless lizards" do
not. Unlike all other reptiles, or even vertebrates, many viperids have a
mobile maxilla with a massive fang attached to it, so this might be grounds for
a new Class (?). They even bear live young, or at least about 1/3 of them can,
some without even forming a shell. Some swim (far better than marine lizards --
I'm not referring to mosasaurs or the like), and some can "fly". Yet they are
still combined into Squamata and there is no problem with snake researchers
that they are descended from within lizards and, they are in fact legess
lizards. Getting researchers to part with the peculiar sense of the need to use
Serpentes as EQUIVALENT to Sauria is the hard part, since this does nothing (as
this thread should be showing by now, if not long ago) but obscure
relationships. Especially since the line of "lizard to snake" is extremely well
known and virtually unbroken and just as gradational as the "artiodactyl to
whale" or the "dinosaur to bird" or the "fish to amphibian" transitions are.

<Perhaps if there was a more varied vocabulary in the terms, this "non-" stuff
wouldn't be so bothersome. Still, after seeing all the examples given, I'd
still think it would be easier to say "dinosaur," "theropod," "maniraptor."
etc.>

  The problem with that kind of easy vocabulary being requested, as I wrote
above and as both Mike Keesey, David Marjanovic and Tim Williams (I think) have
indicated on their own, is that this misleads individuals unfamiliar with the
groups into thinking that these names represent actual scientific entities,
which they clearly do not. The only way to use a scientifically meaningful (and
thus, non-para- or polyphyletic) name is to apply it universally. This
neccessitates certain vernaculars (e.g., "dinosaur") but also ties them to
their clades. That the public misuses the term and this became the norm for
nonspecialist researchers encountering the group does not mean we should
abandon the idea and go on and use paraphyletic names.

  The solution has been to use a terminology of "non-A B", however unfamiliar,
and expand it. It is with use and exposure, not silence, that terminology
expands. If the complaint is that only VP uses this, and only sparingly, this
is not a fault of VP for making unreasonable demands on what are arguably
flexible minds. Rather, it is the opposition and use of a vernacular vocabulary
that promotes the use of paraphyletic gradients in order to continue using that
which is familiar.

<I don't see why not having all pelycosaurs being mammalian has anything to do
with the forgoing of the term.>

  Pelycosauria is a paraphyletic group that even those who study them
explicitly do not use. They favor Synapsida and Therapsida, particularly. Using
"pelycosaurs" itself is only a symptom of the problem I talked above in the
last paragraph I wrote.

<Not all dinosaurs were avian either, yet "non-avian dinosaurs" abounds.>

  This has more to do with the focus on avian evolution and origins (one of the
things vertebrate paleontology has had FAR more to do with than any
neontologist, unspecialist, or even many extant ornithologists have to do
with). Within dinosaurs, it is useful to discuss non-titanosaurian sauropods,
but there are simply not that many of sauropod researchers to make the term
broad in use. Most dinosaur students have a tendency to focus on theropods (and
thus, bird origins) than any other group (second comes ornithischians, in which
you will find another debate on paraphyletic clades, lumping, splitting,
gnawing, gnashing....).

> Interesting, the papers you mention only very quickly
> use the "non-" moniker, before replacing it with an
> actual term. 
> 
> E.g.: "The phylogenetic systematics of the
> polychaetes, i.e. the nonclitellate annelids..."
> 
> "To avoid assigning rank to taxonomic names throughout
> this manuscript, we use the terms "vestimentiferan"
> and "perviate pogonophoran" (i.e., the traditional
> non-vestimentiferan pogonophorans)." 
> 
<I'd say that the invert guys are on the right track by assigning new names to
keep the traditional (and obviously still useful) boundaries in check.>

  But they aren't assigning new names, they are referring to subsets alone:
perviate pogonophoran and vestimentiferan are parts of Pogonophora, not
paraphyletic regards to it. Polychaetes _are_ non-clitellate annelids, and are
monophyletic, unless I miss my guess (I am not an invert specialist). None of
these are new names, or even newly applied, but it shows the authors are making
examples BY using the non- terminology, since it clarifies for the reader. This
is an example of elucidation. Paraphyletic names ONLY confuse and cloud the
reader further.

  I must break this email here for brevity's sake.

  Cheers,

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

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

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