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Re: Rant (was RE: Details on SVP 2002 Part 2)



George Olshevsky (Dinogeorge@aol.com) wrote:

<I say bataar is closer to the albertosaurs than to rex, on the basis of
the shape of the skull, the position and direction of the orbits, the
position and direction of the occipital condyle. I say the reason for this
is plesiomorphy, not synapomorphy.>

  Well, uh, duh? You will resemble your ancestors as much as any relative
descendant. Sorta the rule of a plesiomorphy, and why you must be wary of
them, not use them to support separation. All conditions, including
synapomorphies and autapomorphies, should be considered.

<Bataar and rex are end nodes of two distinct lineages of tyrannosaurid,
one Mongolian and one North American, so they can't be in the same genus.>

  Uhm, there is no logical conclusion here. Being on different continents
does mean you're not in the same genus ... unless "genus" now has a
continental meaning somewhere in it. Any two taxa will be end products of
any evolutionary event, 

<Any similarities between rex and bataar can be chalked up to
convergence.>

  And this outwieghs the evidence favoring them as sister-groups? What is
the counter argument that states that the data supported by others is not,
in fact, more likely to be true?

  If both NA and AS forms of tyrannosaurine were similar to one another,
not just gross size but in various forms of the postorbital, braincase,
and maxilla, premaxilla, and dentary, as noted by Holtz, Carr, Hurum,
Currie, etc., would it not then be a more likely conclusion that they
shared a unique ancestry than either with any "albertosaur". If the
condition of pointy upright horns, a slender snout, no suborbital flange,
etc., were plesiomorphies, would the ancestor have it, or not? *Alioramus*
is a primitive form and permits a gague of the primitive braincase, snout,
dentary anatomy, and dental apparati, on which to assess possible
"earliest known morph" that other, younger forms would have developed
from. This is sort of the operating dynamic all other researchers have
agreed to based on their evidences. What data have you, George, to
publically dismiss this data to conclude that instead they are all
plesiomorphies and that the Asian form is closer to the primitive
"albertosaur" lineage? Just curious.

<What good are 149 characters if 95 of them are question marks? It's
unfair to promote a phylogenetic analysis this way.>

  Really? I could probably code the more "taxonomically informative" taxon
*Alioramus* for less, depending on the matrix. Its also a matter of
character selection. But if I'm hearing that its possible the relationship
of *Dryptosaurus* to tyrannosaurs is problematic because it cannot be
coded for even half the matrix, then this is also what Tom said, and it
is, essentially, true. Some workers work to removing taxa lacking a
certain percentage of the matrix, and check the effect of "?" on the
whole, which is where we get the experiments that lead to understanding
the effect of "?"; but included data helps, and limb anatomy supports the
similarity of *Dryptosaurus* to tyrannosauroids. The recent Wilson (2002)
sauropod phylogeny paper, for instance, has only two taxa, *Diplodocus*
and *Camarasaurus* that can be coded for over 98% of the 300 character +
matrix; many included fall short of the 50% mark, but this does not mean
that taxa like *Titanosaurus colberti* or *Pellegrinisaurus* are less
informative phylogenetically and should be shucked as "crap".

<Suppose more material resolves the question marks and most of them go the
wrong way?  Minor characters such as the position of a condyle or the
location of a foramen could be extremely labile and thus virtually useless
for phylogeny.>

  Position of the condyle changes depending on orientation of minor bones
in the skull, and are, essentially, mechanical in effect. It has been used
to discuss the orientation of the skull in spinosaurs, pachycephalosaurs,
ceratopsians (Dodson goes into immense detail on this in _The Horned
Dinosaurs_).

<Stop calling BCF a fairy tale. It remains the most parsimonious theory
for the evolution of dinosaurs, even if I haven't had the time to write it
all up yet.>

  Parsimony requires testing, and data without data cannot be
cross-checked. That is, I beleive, what Tom was trying to get at. It is,
in fact, a personal theory, and this can be the hardest to loose hold of,
and certainly nearly impossible to look at objectively.

<For one thing, I don't see a heck of a lot of difference between
Daspletosaurus torosus and Albertosaurus sarcophagus, certainly not enough

> for a generic distinction.>

  Yet many workers regard them as morphologically as distinct as *T. rex*
and *T. bataar*, they are temporally distinct, do not co-occur in any
level, and the skull itself shows features relating to widening and an
increase of robusticity in both teeth and jaws, as well as the supporting
framework, that relate to the tyrannosaurines. This is a matter of data,
not who's right. I could certainly say that I think *Elmisaurus* and
*Chirostenotes* should be synonymized, for there's nothing that really
separates them but fusion in the tarsus and finger stuff, but I don't. For
instance, I then look at the *ahem* geographic separation, size variation,
temporal variation, morphology variation, and see the same data can be
used to point the otherway, depending on philosophy. It would be horribly
inconsistent of me to say that I can separate some taxa on basis of time
and geography as "genera", but then reverse this for others. Or that some
features of the bone are "better" than others. Without any
rationalization. How is a process better than a robusticity index? Does an
extra tooth position mean more than the shape of tooth in the socket, or
the shapes of teeth on both ends of a row? What ability is there on my
part to judge how my character is better, and therefore outweighs
another's?

<Daspletosaurus should be sunk as a distinct species of Albertosaurus,
namely, Albertosaurus torosus. If you want to see generic distinction,
consider that Iguanodon bernissartensis and Iguanodon atherfieldensis have
been classified in the genus Iguanodon for three-quarters of a century,
and they're >certainly< generically different.>

  Talk to Norman then. Sure he'd be glad to hear your reasons. Maybe even
on what a genus is.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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