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Re: Fwd: Are dinosaurs really reptiles? (2)



 Nick was kind enough to forward this reply to my earlier query on the ancestry 
of Petrolacosaurus. The 'other David' provided this list from a published work 
by Müller and Reisz, reffed at the end. it must be the latest word.

This list, if it is a good one, should follow a gradual evolutionary path with 
regard to morphology. Let's see if it does.

(and yes, I'm being purposefully 'folksy' about this).

 --+--Seymouriamorpha         
       okay. good start. Somewhere outside of Amniota. But where are 
Gephyrostegus and     
       Utaherpeton? They're a little more plain and ordinary. Have they been 
ignored? 

 |--Diadectomorpha               
      I'm seeing a pattern here: Small, flat-headed and short-toed gives rise 
to big, 
      and short-toed. There's some logic to it. The intertemporal is gone. So 
this must be an
      amniote.Or is it? A fat, slow, plant-eater is the father of us all?

 `--+--Caseidae 
        The pattern of giant, weird, plant-eaters continues. So it must be true.
        No doubt this is an amniote [representing the Synapsida?]. 
          Where are the plain little insect and meat eaters, like Helosuchus 
and Westlothiana? 
         Are we ignoring them because they're not intriguing? At least the tail 
is long here. 
         Didn't early reptiles have long tails? Or was that a secondary 
acquisition?
                                                    
 `--+--+--Mesosauridae        
       Suddenly we're aquatic! With a decidely long premaxilla! And long teeth! 
       And a long tail. And a long neck. And long toes! So derived! So early! 
       This one seems misplaced. 
       Oh, yeah, Modesto said it nested with pareaisaurs (not even on the list).
       
 | `--+--Millerettidae
       Okay. Finally a plain brown, ordinary insect-eater. Long of belly. Low 
to the ground. 
       Don't know if the tail and toes are long or short here. Not preserved.
 
 | `--Procolophonidae
       Oh, man. Now we're back to dull teeth, short tail, short toes and a 
flared skull. 
       Kinda like Dia
s
       Now we're back to long of belly, low to the ground again. With a skull 
like Gephyrostegus.
       Not at all like Procolophon. Not flat-headed.

 `--+--+--Thuringothyris and (Captorhinids)
       This one (and its kin) are decidedly flat-headed. Plant eaters.

 `--+--Brouffia 
       I'll have to pass on this one. Not yet in my data base. A pdf would be 
appreciated.

 > `--+--Paleothyris
       This one is deidedly not flat-headed. With long toes. And it has very 
tiny fangs. 
        Which leads us to...

 `--+--Hylonomus
       Finally, a long tail and long toes. Paleothyris and Hylonomus do 
resemble each other.
       Insects and meat on the diet. Now we're talking...

 `--+--+--Protorothyris
       Another close cousin. Say, isn't this fanged taxon getting uncomfortably 
close to 
       the Synapsida? But didn't we leave those guys way back yonder with 
Casea? 
      
 | |--Anthracodromeus
       I know it doesn' have an intertemporal, but it looks a lot more like 
Utaherpeton and
       Tuditanus. Those darn microsaurs. They don't have an intertemporal 
either and they aren't 
       even amniotes. That pelvis only has room for on sacral vertebra. That 
means this guy really 
       belongs way back there near Seymouria. A reptile imposter!

 | `--Cephalerpeton
     This guy deserves more respect than he gets. I'm wondering why he appears 
here, 
      because he's more like Thuringothyris with that flatish head and those 
great big dull teeth,
      ...like, dare I say it... Casea ... way...back...yonder...

 `--+--Petrolacosaurus
     Suddenly, after all these 'anapsids' a diapsid! Two holes at once! Isn't 
it interesting that he
     went straight for two, rather than dawdling about with one or the other 
for awhile? And 
     that's not all. Long toes. Long limbs. Long neck. Long tail. Sharp teeth. 
The only taxon on this l
     list, other than Araeoscelis [and Anthracodromeus] who remotely resembled 
this one is
     Mesosaurus...way... back ...yonder. [shudder]

   `--Araeoscelis
     yes. A good sister
line: Credit is given where credit is due, but this seems to be very scattered 
famiy tree. I don't have any problem with big lumbering plant eaters giving 
rise to gracile little insect-eaters or visa versa... but the change ought to 
be gradual. Evolutionary. Not like this see-saw.

Next question: What were the five to ten sister genera leading up to 
Herrerrasaurus? No suprageneric taxa please. And please include at least one 
pterosaur.

DP in StL


 Müller, J. and Reisz, R. 2006. The Phylogeny of Early Eureptiles:
 Comparing Parsimony and Bayesian Approaches in the Investigation of a
 Basal Fossil Clade. Systematic Biology 55 (3): 503-511.