[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Benton 1985, etc.



Okay, David, sure more taxa is better than fewer taxa. That goes without saying.
Still, if all you want to do is find out if pteros are closer to one taxon or another, you can find out with a dozen of each. Or five if you want to get down and dirty.


For an outgroup, be safe. Try Ichthyostega.

I've also checked matrices for miscodings: Irmis et al. 2007 and Hill 2005. It's daunting, but it can be done. You asked about time put in? 10 years with time out for meals, sleeping, etc. It's fun, so the work goes fast.

re: Atanassov's thesis: indeed he has a close sister taxon to the Pterosauria. It is a langobardisaur, one of the taxa I employed in my 2000 paper.

re: Triassic pterosaur with parasagittal hind limbs: more common than you might realize.

re: pteros next to the Archosauromorpha. Well, lots of interest there. Benton 1985 nests pterosaurs between Lepidosauria and Trilophosaurus + Rhynchosaurs + Prolacertiformes + Archosauriformes. With Trilophosaurus and Rhynchosaurs actually closer to Lepidosauriformes (they are Rhynchocephalians with unfused ankles) than Archosauriformes, that's a very good nesting. Prolacerta is close to the base of the Archosauriformes, so that also makes sense. The attraction of Macrocnemus to tanystropheids also makes sense, but far from pterosaurs is a problem. The only other nesting that is not reflected in the comprehensive cladogram is Prolacerta with Macrocnemus. In the absence of other taxa, evidently convergence won out here. In my 2000 paper, I deleted first Longisquama, then Sharovipteryx, then Cosesaurus, then Langobardisaurus to see when pterosaurs might begin to nest again with archosaurs, using matrices by Evans, Jalil and Bennett. By the time I got down to tanystropheids pterosaurs shifted back to the archosaurs. Not saying that would happen again using a more comprehensive set of characters, but it did happen once.

In 23 years since Benton 1985, no one has published a matrix that includes any lepidosauriformes with pterosaurs. If you can find one, please send it to me. That's a powerful a priori paradigm at work.

You wrote: "No, I can't imagine that finger IV grew secondarily, so it cannot have done that"? I'm not saying you're wrong; I'm saying that if you're right, you're right for the wrong reasons.

Parsimony is the reason I use.

You wrote: *_WRONG_*. Benton had Younginiformes (as a whole!!!) and "Lepidosauriformes" derived from a common ancestor, and he had that common ancestor and Archosauromorpha derived from another common ancestor. This common ancestor is *_NOT_* "Youngina and kin". Why do you keep making such confusions? An ancestor on a cladogram is a node, not a terminal taxon!

It's shorthand, David. Youngina and kin means Younginiforms + more primitive diapsids.

You wrote: Why can't it happen that, at least with our imperfect knowledge of the imperfect fossil record, two large groups can be sister-groups of each other?

That's a world view that is the current paradigm. That world view permits pterosaurs, ichthyosaurs and diadectids, among others, to remain mysterious and poorly connected from other amniotes. This results from using suprageneric taxa and just a few dozen taxa at most (i.e. your suprageneric "two large groups"). A comprehensive cladogram, on the other hand, using species and a few hundred taxa demonstrates that such enigmas do indeed have close generic sister taxa somewhere on the tree. And you'll be able to chart and see the spectral blend of morphologies across the tree.

You wrote: but the unpublished pterosaur with the parasagittal hindlimbs certainly does smell like a dinosauromorph, so we better both shut up till it's published.

Try not to hang your hopes on just one character. I'll just hazard a guess, but I'll bet this unpublished pterosaur has a prepubis, an elongated pedal digit V, hyper-elongated manual digit IV, multiple cusp teeth, chevrons parallel to the centra, an elongated coracoid, a sternal complex (interclavicle + clavicle + sternum), a non terminal naris, an antorbital fenestra without a fossa and other characters no dinosauromorph has. As mentioned earlier, some pterosaurs have a femur with an inturned head, just like dinos.

re: Huehuecuetzpalli: you wrote: What is so pterosaurian about it? Well, its actually closer to Cosesaurus, which leads to pteros, but here goes:

1. non terminal naris
2. ascending process of premaxilla extends beyond naris
3. low distinct coronoid process (a bump)
4. posteriorly sharp quadratojugal making poor contact with quadrate
5. short descending process of squamosal
6. clavicles, interclavicle
7. posterior lean to quadrate
8. eight cervicals (pre-scapula verts)
9. low scapula
10. poorly ossified carpals (phylogenetic, not ontogenetic character -- this is how the centralia migrate to become preaxial carpals and pteroids)
11. manual digit IV is the longest
12. metacarpals III and IV subequal
13. manual digit V reduced but retaining three phalanges
14. fibula less than half diameter of tibia
15. unfused tarsals
16. metatarsals III and IV subequal and longer than I and II
17. pedal digit IV the longest
18. Metatarsal V short and torsioned
19. Pedal 5.1 elongated.
20. Tail chevrons are preserved parallel to centra. Was this their orientation in life?
21. Posterior tail attenuated.
22. and it's the right size