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

Darwinopterus notes



[This was sent a few days ago, Technical glitch evidently prevented its reception. A few minor changes added.]

Free Darwinopterus download:

http://rspb.royalsocietypublishing.org/content/early/2009/10/12/rspb.2009.1603.full.pdf

First of all, congratulations to the Lü team for a series of spectacular finds. The uncovering of that tail and toe is incredible.

Second, I'm disappointed that more taxa were not included in the analysis. And I'm also disappointed to read this from the Suppplmentary Data: "The search was terminated at 500,000 trees due to memory limitations." That's a sign that something is wrong. The Lü study needs to use more of the available taxa.

Yes, Darwinopterus is, as it appears, a sort of Germanodactylus AND unique enough to merit it's own genus. On the same note, lots of nominal Germanodactylus specimens need their own genus. They have a wonderful untold variety.

When you include more taxa than the Lü team included, Darwinopterus nests nowhere near any of the four origins of the pterodactyloid clade. Darwinopeterus nests in the middle of several nominial Germanodactylus specimens and very close to the Karlsruhe specimen, SMNK-PAL 6592, ironically known for its long metacarpals and long legs. And there's a reason for that...but that involves other long- legged taxa.

On a happy note: I see that Scaphognathus and Dorygnathus are moving up the ranks, FINALLY, closing in as sister taxa to the Pterodactyloidea! THAT is new and THAT is starting to match earlier findings (published as an abstract (Peters 2007) in the Flugsaurier papers). Just add several tiny taxa, several specimens of Dorygnathus and Scaphognathus and a few dozen more characters and all will resolve to a single tree.

Third, while the short metacarpal/ulna ratio is VERY rare, it also occurs 7 taxa down from Darwinopterus in SMF a. M. No. 4072, and Mesadactylus by convergence and both of these have ratios atypically shorter than surrounding sister taxa. So such a character is not unique within Pterodactyloidea. I see neither tiny taxon was included in the Lü team study.

The reduction of the metacarpal/ulna ratio in Darwinopterus is matched by a rare ulna > tibia character state, also found by convergence in SMF a. M. No. 4072 and B St 1967 I 276 (also by convergence in ornithocheirids and nyctosaurs)- but in no sister taxa. So, in Darwinopterus (judging by surrounding Germanodactylus taxa), as the legs became shorter so did the metacarpals, both of which are derived according to the larger suite of characters. Note: such unique characters are STILL not enough to make them sister taxa.

The opposite holds true for those long-legged, long-metacarpal taxa, but there's an untold twist in Pteranodon and Nyctosaurus.

Fourth, while the elongated pedal digit V is great to see finally published, you'll find similar pedal digit Vs on MOST pterodactyloid- grade pterosaurs when you look for them. Like Darwinopterus, most of these are tucked under the metatarsus. Yes, most Pteraichnus trackmakers have short pedal digit Vs and they all come from just a few clades, even so, there are some surprises.

Fifth, the long tail and fifth toe can be seen on several Germanodactylus specimens, but at present you have to look for the telltale ridge in the light matrix covering. I can send samples for where to look. My sense is this is a reversal in germanodactylids because predecessor taxa (most small forms) have a long tail, but it is not nearly as robust. It's wonderful that such a tail and toe has finally been uncovered and published. Now I don't have to explain as hard when I show the same in reconstructions. It's also time to take certain specimens off the walls and dig out the toes and tails!

I wish the Lü team best wishes and again, congratulations on a great and extremely important find.

David Peters
St. Louis

davidpeters@att.net