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Re: Phytodinosauria



[I'm swimming in uncharted waters, so if anyone has any ideas as to
 how I might have handled this differently, please let me know.  I
 rejected a message George sent to the list because it contained much
 more quoted material than new.  However, I did send it to Jonathan
 because George's message was in response to one of Jonathan's.
 Jonathan has responded to the list.  Below is his response which
 seems perfectly acceptable and relevant to the list, but contains
 quotes from a message none of you saw... -- MR ]

At 04:16 PM 9/29/96 -0400, Dinogeorge wrote:

>>         This describes Eoraptor. 
>
>Not at all. I have a photo of the skull in front of me, and even though the
>photo is not of the best quality, the teeth look nothing like ornithischian
[...]
        Sereno, in his article, points out that they are somewhat
leaf-shaped.  I noted, while examining the cast of the animal at SVP '95,
that they did indeed appear to be leaf shaped.  No, they are not fully
ornithiscian/sauropodomorph, but they do not look like "normal" theropod teeth.

>Tooth shape can be quite distinctive within Archosauria and should not be
>omitted from any cladistic studies (horrors). And--how could you possibly
>tell whether the "leaf-shape" was "genetically in the genome already"?

        I would never *Dream* of ommiting it from a study, but I will not
base a major clade on it alone (unless my computer tells me to, and then
with reservations).
        I would say that there is some predisposition, either genetic or
selective, for this tooth form, based on the fact that it evolved
independantly at least twice.  If you wish to say that therizinosaurs are
"phytodinosaurs", this is obscured.  I cannot tell *for sure* that it is
"genetically in the genome", but AI can suggest that this is a possibility,
which is all I did.

>Sauropods and "pre-anchisaurid" prosauropods do not have such ilia, and
>they're herbivores.

        Somehow, the idea that an Organism Formerly Known as Brontosaurus
and a Lesothosaurus would need the same iliac structure is pretty funny.

>>Bakker gives one further character, the "double breast bone,"
>
>No, Bakker places this character at the node uniting sauropodomorphs and
>ornithischians in his phyogenetic tree in _The Dinosaur Heresies_.

        Uh... if that's how you read it...

>You misunderstand. I am arguing against placing saurpodomorphs at the base of
>Saurischia by noting that it would make theropods secondarily carnivorous

        No, you're not.  Your statement was:
        "Indeed, if sauropodomorphs are placed at the base of "Saurischia"
between Ornithischia and Theropoda, then (most parsimoniously) the common
dinosaurian ancestor was herbivorous and theropods were secondarily
carnivorous."
        Which is simply not true.  You have two trees where this happens,
from my example, one in which Dinosauria becomes herbiverous (1 step) then
Theropoda becomes carniverous (1 step), or Ornithiscia and Sauropodomorpha
become independantly herbiverous (1 step each for 2 steps).  These two trees
are equally parsimonioius.

>unless herbivory evolved twice in neighboring clades (Ornithischia and
>Sauropodomorpha), which is less parsimonious than assuming it evolved once.

        Not if there is but one character uniting the Saurischia, in which
case you're back to a trichotomy.

>Well, you can take a horse to water...

        But even a horse won't drink water that smells paraphyletic...

+-------------******ONCE AGAIN, NOTE NEW E-MAIL ADRESS******---------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
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|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
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