re: Pisanosaurus and Effigia

[David Peters <davidpeters@att.net>]

Thank you Bill,

Sterling Nesbitt reported and photographed a boot on the pubis of Effigia. 

An anonymous reviewer said this is not so. 

The closest sister taxon to Effigia (based on well over a hundred characters) 
has a boot on the pubis, according to published sources. 

Beyond this proximal taxon pubic boots are rare, so the character is extremely 
minor. 

Perhaps it is best left as a question mark. It certainly isn't worth the 
thousand dollars needed to make the trip. Not when it's only a single box score 
in a matrix of 25,000. And, after all, this is only an avocation.

There _are_ practical limits to data gathering. 

I should eye with suspicion, I suppose, all present and future analyses that 
report a boot on the pubis of Effigia. It may or may not be there. Or for that 
matter, we should all eye with suspicion any matrix that uses any published 
matter for data. Right? Or for that matter, we should eye all data matrices no 
matter their source with suspicion. After all this is science and we should 
test everything. Trust nothing. 

I try.

And even direct observation can be deceiving, as I've learned personally and 
have noticed the fault in others. 

Again, there are practical limits.

For now, whether the boot is present or not, it matters little. The damage is 
done. I've seen worse reviews, as I'm sure many of us have.

Denticles were not described (by Irmis, et al.), nor were they visible (to my 
eye looking at photographic images published in Irmis, et al.) on Pisanosaurus. 
Ridges, yes. Denticles, no. 

And if anyone can appress the metatarsals of Effigia to form a theropod-like 
metatarsus, I'd like to see it. From what I can gather, I and IV fall slightly 
behind II and III with gaps present despite strongly overlapping proximal ends, 
again, as in sister taxa. This one could actually be a judgment call. And 
again, it matters little because proximal sister taxa go both ways.

The point is: A matrix of 25,000 boxes and a comprehensive taxon list can have 
dozens of misinterpretations and missing data and with corrections not a single 
branch shift, let along a major branch shift. That takes hundreds of 
corrections -- and all in the same direction! It must be remembered that 
typically half of the corrections one makes to a matrix can confirm apparent 
nestings. Smaller matrices, especially those with less inclusive taxon lists, 
are not as robust, at least in my experience. 

That's why deletion tests are so wonderful. You can throw out large chunks of 
random data (including "bad" characters and taxa) and still arrive at the same 
result. You can also test your results with a completely separate matrix using 
unique characters and arrive at the same result, as I have-- but then, I did 
use published data. 

Just ranting. I'll get over it.

Best to you, Bill,
David Peters


David,

I would recommend visiting the AMNH and the PVL to personally examine the
type specimens (as Randy Irmis and Sterling Nesbitt did) to answer these
questions.

best,

Bill Parker




Does Pisanosaurus have serrations or denticles on its teeth?

Bonaparte doesn't show them. An "expert" says it is so.

Same "expert" said Effigia does not have a boot on its pubis and the
metatarsals were closely appressed, contra the images in Nesbitt
2006. Are these so?

David Peters
davidpeters@att.net