Re: Protoavis?

["Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>]

At 05:08 PM 10/19/97 -0700, you wrote:
>OIC.  _YOU_ jump to conclusions and proceed to browbeat me for thing I
>never said, and that's somehow _my_ fault for not phrasing things in the
>particular jargon dialect that you prefer to think in. 
        Okay, time out. Let's all catch our breaths and compose ourselves...
        Ok, I'm calm, are you? Let's proceed...

>Perhaps you ought to wake up and realize that I CONSIDER THIS LIST TO BE
>A SOURCE OF INFORMATION, AND MY ORIGINAL MESSAGE WAS A REQUEST FOR
>INFORMATION.
        This was not clear. Considering the contentuous subject matter, it
is not surprizing that it was misinterpreted. For my part, I apologize for
not understanding.        

>Is there even _one_
>so-called "professional" on this list who doesn't regard simple
>questions as personal attacks on his worth as a human being? 
        a) I personally wouldn't call myself a professional
        b) Your post was not taken as a personal attack so much as another
instance which might serve to perpetuate misconceptions concerning a subject
which has already been so misconstrued as to represent a blemish on the
reputation of vertebrate paleontology, not to mention on the records of the
participants. Any sensitivity with regards to this issue may be traced back
to devisive nature of the questions involved. I would suggest that you try
not to take the reaction personally, and in future perhaps tread more
cautiously on this ground.

>Why is it that a simple question is seen as a call-to-arms for the DinoList
>Inquisition?  
        Hmm... never been called that before. I always preferred the
"Cladistic Assassin" myself... :)

>Would it be too much to ask that you remember that not everyone on this
>list is a degreed paleontologist, and not everyone is interested in
>getting the jargon exactly right? 
        My point was that the jargon is jargon for a reason. Hard as it may
be for you to believe, scientists do not sit around making up jargon to
confuse the layfolk. Jargon is used to aid in precision of thought and
communication. Bear in mind that all language is, in a sense, jargon. The
reason scientists restrict their speach is to ensure that all parties have a
chance to understand all of the connotations. Vernacular speach is loaded
with implications and subtle innuendos which vary among speakers, and are
not always adequate for the purpose. Indeed, sometimes vernacular speach can
obscure a fundamental point.
        A prime example of this is the "dinosaur-bird" dichotomy which you
and several others have brought up in this context. By invoking a
distinction between the two forms, you artifically create a sense of
distinctness (in a vernacular as well as scientific context) which obscures
the inclusion of the latter group within the former. This may result in
confusion on other topics, and lead to false premises.
        Jargon *can* always be explained, vernacular speach *must* always be
explained.

>Would you [object] this much if we were talking about, say, dogs vs.
>other members of Order Carnivora?  Would you be insisting that I say
>"canid carnivores and non-canid carnivores?"  I didn't think so.
        It depends on the context, the point you are trying to make, and the
relationships within Carnivora, however it is currently defined.

>Be that as it may, if we had only one partial fossil of a serval, and no
>other fossils of any animal in the Felidae,nor of any potential ancestor
for >it, [...]
        As an aside, I should note here that the presence or absence of a
"potential ancestor", however that status may be determined, is usually
irrelevant for the purposes of determining relationships.

>we couldn't say a whole lot about exactly how the
>serval was related to other carnivores.  Unique skull, unique teeth
>pattern, unique legs and feet . . . 
        I have never played with carnivores all that much, so I couldn't
say, but somehow I doubt the situation would be as bad as you suggest.
Anyone with experience in the field of felid phylogeny (a little
alitteration always alerts the auditory apparatus) care to comment?

>Nor, with only one fossil of
>_Protoavis_ can we say a whole lot about exactly how it was related to
>other dinosaurs.
        Hardly.
        Dr. Chatterjee makes an interesting case for a relationship. If you
know anything at all about birds, I suggest you have a look at his
illustrations and compare them to the osteology of birds. Then, if you still
aren't convinced, I believe he has a paper forthcoming.
        If we cannot tell the relationships of an animal from one skeleton,
we are indeed persuing the largest scientific dead-end since neptunism. If
we cannot use basic comparative anatomy to deduce phylogeny, or if we have
to have more than one animal to do it, we might as well just throw all the
non-avian dinosaur fossils away and start over.

>Cladograms are not Divine Revelation.
        I am NOT going to start this again. Suffice it to say, this is
irrelevant, and I will not get into another meaningless argument over an
established scientific practice. Especially not when the opening shot is
couched in such an unreasonable manner.

>They can be wrong.
        This is not news to anyone.

>> Is the presence of birds
>> delimitied by the oldest occurance of feather preservation? 
>
>Given how similar some theropod dinosaurs are to primitive birds, in my
>amateur's opinion, the answer is yes.
        Unless _Archaeopteryx_ is the ancestor of all later birds
(unprovable), then birds HAD TO exist *before* _Archaeopteryx_.
        What does the similarity of the two groups have to do with it? In
order to succinctly hypothesize that a specimen is a "bird" (Avialae,
Gauthier 1986), one must simply present a well supported phylogenetic
hypothesis which suggests that it is a decendant of the most recent common
ancestor of _Archaeopteryx_ and _Corvus_ (happy Pete?). Chatterjee believes
he has done this. No feathers involved.

>For Late Jurassic and earlier
>fossils, you cannot assume you have a bird based only on skeletal
>characteristics.
        This is simply wrong.

>Remember, if it didn't have feathers _Archaeopteryx_
>would be classified as just a small, odd theropod.  Only the feathers
>mark it definitively as a bird.
        However, were an animal outside of the archie+modern birds clade to
be discovered with flight feathers, then later analysis would suggest it as
a bird, even if it had no feathers. The feathers *diagnosed* it as a bird,
but birds can be *diagnosed* without feathers. See _Ichthyornis_ and
_Hesperornis_.
        
>And remember also how _Mononykus_ has
>flip-flopped from bird to nonbird several times based on different
>interpretations of its skeletal features. 
        If _Monoykus_ is discovered to have long birdlike feathers, then
that will be substantial evidence that it is a bird. However, if someone
were to later demonstrate that the symetrical feathers of
_Protarchaeopteryx_ were not indicative of secondary flightlessness, then
that line of evidence might go right out the window. With enough evidence,
it should be possible to demonstrate its affinities without feathers.
        The "flip-flopping" you see are the result of homoplaisy,
evolutionary reversals and/or convergences, which are present in basal
maniraptorform theropods. This is a normal problem in systematics, and has
nothing to do with the presence or absence of feathers (at least, it shouldn't).

>Cladograms can be wrong.
        Por supuesto.

>Subjective interpretations can be wrong.
        Certainly.

>I want to see a smoking gun, preferably with fingerprints on it.
        Then you will be waiting a long time. As it is, paleontology
sometimes has to stretch the limits of interpretation beyond what should
make even a relatively "liberal" scientist squeemish. We have been
outstandingly lucky to get the evidence for bird origins that we have. In
many other areas, we have not seen, nor are we likely ever to see, "smoking
guns" of the type you describe.
        No scientist who limits himself to "smoking guns" will find
paleontology that enjoyable.

>In the
>case of _Protoavis_, that means unmistakable evidence of feathers, and
>preferably flight feathers.  
        Like I said before, feathers may not be only a "bird" trait.

>Excuse me?  The relative age of two fossils should play no part in
>determining their phylogenetic  relationships?  OK, I hereby declare
>that _Protoavis_ is a direct descendant of _Deinonychus_ by way of
>_Archaeopteryx_.  There.  Problem solved.  
        Excuse my imprecision. I meant in terms of who is more closely
related to whom (evolutionary propinquity), not the alpha-phylogeny (is that
a word?) of who descended directly from whom. While we cannot ever prove an
ancestor-descendant relationships, stratigraphy and paleobiogeography may be
most helpful in disproving such an association. Generally, especially with
terrestrial vertebrates, where the fossil record is quite scanty, such
hypotheses seem to be rather rare.
        However, most terrestrial vertebrate workers whose methods are
reproducable and consistant (i.e. cladistic) seem to prefer to leave
stratigraphy out of their analyses. Why? Well, because the terrestrial
record is so poor that it biases the data. Is this a rational approach? At
least one group thinks not, and are testing their assertions using computer
models. George Olshevsky will be pleased.
        As I said before, one might use the stratigraphy to evaluate a
phylogenetic hypothesis, or to choose between competing ones. However, I
cannot see using it to prove that _Protoavis_ is not a bird in a
reproducable, internally consistant manner. A stratocladist might disagree.

>PS: According to the geology I learned, phylogenetic relationships play
>no part in stratigraphic correlation.
        I never once mentioned CORRELATION. I said that stratigraphic ranges
for taxa are based on the phylogenetic relationships. For example, if
Dinosauria is construed to not include birds, it ranges from the Triassic to
the Cretaceous. However, including birds, it ranges from the Triassic to Recent.
        Thus, the use of the range of birds to suggest _Protoavis_ is not a
bird, as you imply, is fallacious since you used the phylogeny to determine
the stratigraphic range, then used the stratigraphic range to make
meaningful statements about the phylogeny. Circular.

        :)
        Wagner
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
        "There's a fine line between stupid and clever."  -- Spinal Tap