Re: Cladospeak (Mammalia, Crurotarsi)

[NJPharris@aol.com]

In a message dated 9/3/01 3:14:54 PM Eastern Daylight Time, 
kinman@hotmail.com writes:

>  Cladospeak reminds me of lawyer-speak

Indeed; they sound similar because they both need to be *explicit* and 
*thoroughly defined*.


>  and by the time you get through 
>  defining and clarifying, the original point is totally forgotten.  And I'm 
>  not sure how "strong synapomorphies" might differ from "significant 
>  syanpomorphies"

There is no such thing as either.  Honestly, looking for "significant" 
synapomorphies is a bad way to go, though I'm sure we all do it to some 
degree or another ("wow, this is really unusual; the two groups sharing this 
feature *must* be related!").  Alas, for a few years there, I was convinced 
the arctometatarsus could not possibly have evolved more than once.

Actually, fixing on a hypothesis--even just a hunch--and amassing evidence in 
support of that hypothesis is not such a bad thing.  Many interesting and 
valid discoveries have been made that way.  But in order to be scientific, 
you have to be prepared to show that the totality of evidence in favor of 
your hypothesis is greater than the totality of evidence in favor of any 
competing hypothesis.  In other words, you can't focus on the plusses to the 
exclusion of the minuses (and just to be totally clear, I am making a general 
point here, not accusing HP Kinman of any scientific wrongdoing).


>  [is "derived" better than "advanced"?---or are they both a cladospeak 
>  faux-pas, no-no, bad-bad].

"Derived" is fine in my book.  The idea is to communicate the concept of 
"different from one's ancestors" without making it sound like "better than 
one's ancestors".


>        This [the mammalian three-ossicle ear] is a "significant" 
synapomorphy (to 
>  use your terminology), or 
>  strong synapomorphy in my parlance.  It is so significant (i.e., so 
>  "strong") that most mammalogists continue to use this as their definition 
of 
>  mammal (Class Mammalia)

But is that necessarily wise?  There is not all that much difference between 
a double jaw joint and a three-ossicle ear, and I for one would not be 
totally shocked to learn that the articular/malleus and quadrate/incus had 
de-coupled from the jaw joint in more than one lineage.


>  and the cladistic Mammaliformes and "crown group 
>  Mammalia" are just irritating and confusing hinderances to communication 
>  which resulted when cladists decided to fix something that wasn't broken 
in 
>  the first place.

It seems to me that giving all of Linnaeus's amniote classes crown-group 
definitions was an attempt at standardization.  I thought you liked 
standardization :-).


>      As for Crurotarsi, I am not saying "it MUST be bad".  I am saying the 
>  synapomorphies supposedly supporting it as a clade do not appear 
significant 
>  (i.e. not strong), and compared to the mammal synapomorphy, they are 
>  downright "weak" (comparatively insignificant).  

But can you come up with some better/more numerous ones for 
Ornithosuchidae+Dinosauriformes?  In this game, the best supported hypothesis 
wins, even if it isn't perfect.

Also, if your aim is to suggest that dinosaurs might have arisen in multiple 
lineages from within Crurotarsi (something you have suggested within the past 
week or so), you not only have to deal with the synapomorphies thus far 
advanced in support of Dinosauria and Crurotarsi, but with those of 
Dinosauriformes and Ornithodira (since these are still perfectly valid 
synapomorphies of a clade containing dinosaurs and dinosaurlike archosaurs, 
even if pterosaurs did converge on some or all of them) as well.

--Nick P.