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RE: something's wrong here: Qianosuchus phylogeny



Most of your complaints are ridiculous, as you often say "derive x from y" when in reality, the situation is "derive the common ancestor of w and x from their common ancestor with y". The way to argue against phylogenetic relationships isn't by stating a few reversals you personally find incredulous, or noting a couple characters you find to be unparsimonious. Obviously it's to perform a phylogenetic analysis. Which you did, but the character list is unpublished. If it's anything like your pterosaur analysis character list, it's untrustworthy. Most of those were correlated with others and/or incorrectly formed. For instance-

"19. Naris size/shape: 0) narrow to oval; 1) huge; 2) rotated dorsally; 3) secondary naris present."

This is a terrible character. The states aren?t equivalent at all. State 0 is naris shape, state 1 is naris size, state 2 is naris orientation, state 3 is number of nares. Divide into 4 characters, each describing one particular variable.

So despite your laudable goals of more characters and low level OTU's, your character construction flaws your results. For what it's worth, I tried an archosaur analysis with 92 taxa and 132 characters (from Benton, Parrish, Sereno, etc.) and always got mostly standard results as far as which taxa were crurotarsans vs. avemetatarsalians, and which were basal to crown archosaurs. And yes, Triassolestes, Turfanosuchus and Pseudohesperosuchus were included. Crurotarsan phylogeny was quite odd though, and more characters were needed for so many taxa.

Mickey Mortimer

From: david peters <davidrpeters@earthlink.net>
Reply-To: david peters <davidrpeters@earthlink.net>
To: dinosaur@usc.edu
Subject: something's wrong here: Qianosuchus phylogeny
Date: Fri, 31 Aug 2007 14:09:23 -0500 (GMT-05:00)

Thanks to Matt Celeskey, I now have the pdf of the Qianosuchus article. So Fabio, if you're still interested, I can send you a copy.

The strict consensus tree in the accompanying pdf file looks 'traditional.' By that I also mean 'bogus' as many of you already know. Let's start the rant right here:

Hyperodapedon
Prolacerta
Erythrosuchus
Euparkeria
Proterochampsidae
     Scleromochlus
          Pterosauria
          Lagerpeton
          Marasuchus
          Ornithischia
          Sauropodomorpha
          Herrerasaurus
          Theropoda
     Ornithosuchidae
     Qianosuchus
     Phytosauridae
          Gracilisuchus
     Postosuchus
          Crocodylomorpha
     Stagonolepidae
          Fasolasuchus
               Ticinosuchus
               Prestosuchus
               Saurosuchus


Prolacerta > Proterosuchus > Erythrosuchus > Euparkeria is all just fine. Then the trouble really starts.


Can anyone tell me how you derive Proterochampsidae from Euparkeria? That's quite traditional in many trees. But it's so wrong. Can't we find any other taxa to fill this gap? What about Vjushkovia?

Then, can anyone tell me how you derive the so-called 'Crurotarsi' from Proterochampidae? Phytosauridae, yes. But say no to Stagonolepidae, Gracilisuchus, Rauisuchidae, crocs and the rest. Look above the ankles! Look at the nares!

Also arising out of Proterochampsidae: Scleromochlus! What??? Put those two side-by-side in a PowerPoint presentation and listen for the giggles. They almost could not be more different.

But wait, it gets worse: Pterosaurs arise from Scleromochlus and its unknown sister taxa!!! Suddenly the smallest hands in all creation become the largest! And that stub of a metatarsal 5 becomes a highly specialized retractable toe??? Bogus. I know, I know, we're talking about sister taxa here, but you have to go pretty far back in this family tree to get that toe to grow back.

Then Lagerpeton arises from the sister to pterosaurs? I don't think so. It's closer to Tropidosuchus and then Chanaresuchus and then Proterochampsa. So we skipped a generation. And toe five is gone again.

Out of Lagerpeton arises Marasuchus, even though the hips and toes don't match. Now it would be good if Marasuchus could arise from a sister to Scleromochlus, with which it shares so much more. Again, we skipped a generation.

Last but not least, theropods arising out of sauropods and ornithischia? Shouldn't that be the other way around? Aren't theropods closer to Marasuchus in every way? Sharp teeth, reduction of digits, etc. By the way, toe five makes a return in some of the above.

No wonder the authors were not able to figure out where Qianosuchus nested. They needed the following taxa: Triassolestes, Turfanosuchus, Pseudhesperosuchus. They need updates to Ticinosuchus. They also need more characters. That dorsal nose in Q. is very much like what is seen in aetosaurs, by the way, which are also derived from Ticinosuchus. So, not sure if that tall slender tail of Qianosuchus is swimming. Especially considering that the transverse processes that would have anchored the tail rectractors are really hard to find.

The world view of traditional workers is that someday some series of taxa will fill in those currently untenable gaps in the evolution of one form into another. There's a simpler solution. It's called parsimony. We have enough taxa to make it work so that sister taxa seem to blend into one another morphologically, but they must be used. And when all the work is done, you have to step back, take a look at the whole thing and ask yourself: "Does this make sense?" remembering that evolution works in tiny increments.

Last rant: specimen-based studies: good. Suprageneric-based studies: bad, as shown above.

David Peters
St. Louis