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

Re: where have all the etc.



I wrote earlier: Name a taxon that would be a better sister taxa. I'll
plug it in.

TW wrote, and DM said more or less the same thing: As others have
mentioned, perhaps the problem lies in an insufficient number of
characters, rather than in the choice (or number) of taxa.

>>>> Okay, let me repeat what you are saying in my own words as I
understand it: There is a 'problem' in that I have insufficient
characters in my analysis. But in this partcular rabbit hole leading to
Wonderland the problem is that I have complete resolution and all sister
taxa resemble each other. My friends, that's no problem. That's a
solution.



TW also wrote, quoting Brochu: "Most analyses agree that Parasuchia
(phytosaurs), Aetosauria, and the various ?rauisuchian? lineages are
close relatives of Crocodylomorpha (Gauthier, 1986; Benton and Clark,
1989; Sereno and Arcucci, 1990; Sereno, 1991a; Parrish, 1993; Juul,
1994; Gower and Wilkinson, 1996; Fig. 2 ). All of these animals
(pseudosuchians) have a so-called ?crocodile-normal? ankle, with a
rotary ankle joint "

>>>> You'll note that each of the analyses uses some or many
suprageneric taxa, and that each one has 13,  14, ? 11, 20, 9, ? taxa in
total. Now granted they all focused on the archosauriformes, but none
include any Choristodera, Doswellia, Cerritosuchus, Silesaurus,
Lotosaurus, Pseudhesperosuchus, Tropidosuchus, or various Youngina (they
break up into separate species at least under closer examination) to
name a few. Put these raisins in the pot, stir and see what comes out.
It's not your mama's oatmeal anymore. A good cladogram can accommodate
an unlimited number of new taxa but only because it has a very large
number to begin with. These smaller early attempts need to be reexamined
to see and test whether or not a crcoc-normal ankle was indeed a single
occurance, or did it happen more than once. I'm merely saying that since
no one has created the umbrella cladogram yet, all prior work should be
judged as suspect until that the umbrella has been established. Sure
there is some truth here and there in those early works. But in certain
corners they disagree with each other, and if there are still incerta
sedis taxa and clades back there, and there's a single tree up here,
then prior work needs to be reexamined and expanded.

That's all I'm saying. It's like that crude and simple original drawing
of the enigmatic skull of Jeholopterus. They stopped too soon. They need
to dive deeper to find the treasure.


DM wrote: What, you have only 150 or so characters in your matrix, and
in spite of this you are so certain of your conclusions?!?

>>>>> When you have a single tree and everything makes sense, then the
end of the road has been reached. I'm sorry to hear that the same cannot
be said of your theropod work. It must be frustrating. Do your ratio
entreaties stem from this frustration? Or is there a reference that
tests this minimum ratio hypothesis? If the latter, please suggest a
reference. Referees have brought this up, suggesting I use 20,000 taxa
and as many characters, so this ratio-thing has been on my mind. As you
can well imagine, the prospect of so many taxa is daunting and I am not
that ambitious.

David, you mentioned you would need a week or so to get your 10
characters that will link the flat-headed, dorsal naris archosauriformes
with the tall-headed hook-nosed ones. No problem. I can wait.




DM wrote: I'll be in Paris to write my ~ Master's Thesis under the
supervision of
Michel Laurin. He could well have something.

>>>>>> He does. My manuscript, cladogram and I think a matrix. Good luck
on your thesis!

David Peters
St. Louis