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Re: Wukongopterus and Darwinopterus



Nicely done, David. 

Seems to be a lot of trouble getting decent resolution here. Flugsaurier 
2007:27 presented a solution that works. Test it. More characters, more taxa, 
brings better resolution. 

David Peters


 

On Nov 24, 2009, at 7:00 PM, Unwin, David M. (Dr.) wrote:

> Darwinopterus – a true test of pterosaur phylogeny?
> 
> In response to comments by A. Kellner and D. Peters:
> 
> 
> AK (Nov 17th 2009) asked:
> “By the way, what are the differences between Changchengopterus and 
> Darwinopterus? I hoped to learn more from it, but Lü et al. did not compare 
> both taxa in their paper.”
> 
> The diagnosis given by Lü et al. distinguished Darwinopterus from all other 
> pterosaurs described up to that point which (obviously) included 
> Changchengopterus (variously spelled “Changchengopterus” and 
> “Changhengopterus” by Wang et al. 2009). Metric data suggests that the 
> holotype and only known specimen of Changchengopterus is distinct from all 
> described specimens of Darwinopterus. For example, wing-phalanx 1 is longer 
> than the tibia in Changchengopterus, but shorter in Darwinopterus – this can 
> easily be established by comparing the metric data published by Lü 2009 and 
> Lü et al. 2009. 
> 
> 
> DP (Nov 16th 2009) asked:
> “Shall we keep Wukungopterus and Darwinopterus separate for awhile? Or, which 
> came first according to the rule book?”
> 
> I have now scored “Wukongopterus” for both the Lü et al. 2009 and Wang et al. 
> 2009 cladistic data sets and, in both cases, where comparable, the character 
> state codings are identical to those of Darwinopterus. Morphometrically 
> speaking these taxa also appear to be identical. Evidently, therefore, there 
> is a good case for synonymy (with Darwinopterus taking precedence as it was 
> published well over a month before “Wukongopterus”). It remains to be seen 
> whether the small differences in the dentition and jaw shape that I noted 
> previously (see DML, Nov 15th 2009) are sufficient to justify the retention 
> of “Wukongopterus”. They might, for example, be an artefact of compaction 
> damage. 
> 
> 
> A. Kellner (Nov 17th 2009) commented:
> “While describing Wukongopterus we run [sic] into two problems: first, we did 
> not have a complete skull, showing the confluent external naris and 
> antorbital fenestra.”
> 
> Interesting point. I presume from this that Wang et al. now assume that 
> “Wukongopterus”, like Darwinopterus, had a confluent nasoantorbital opening 
> (this supposition is supported by an illustration accompanying various news 
> reports on “Wukongopterus” which shows it with a confluent nasoantorbital 
> opening). So, having recently managed to replicate Wang et al’s 2009 
> phylogenetic analysis, I reran it scoring this character as present for 
> “Wukongopterus”. It had no impact on the analysis, which still recovered 
> “Wukongopterus” in a trichotomy with Dorygnathus and a bunch of other basal 
> pterosaurs, including Dimorphodon and a series of Triassic taxa that, 
> according to this analysis (and as in Wang et al. 2009) are more derived than 
> “Wukongopterus”. 
> 
> As mentioned above, I also scored Darwinopterus for the Wang et al. 2009 data 
> set. It is isometric with “Wukongopterus” which can thus be safely deleted 
> from the analysis. According to Wang et al. 2009 “Wukongopterus” has missing 
> data for 34 out of the 89 characters used in their analysis (and is thus 62% 
> complete). Darwinopterus adds data for 28 of these characters and is thus 93% 
> complete. So, I reran the Wang et al. 2009 data set using this near complete 
> sequence for Darwinopterus/"Wukongopterus". To be fair, the taxa 
> Scleromochlus, Angustinaripterus, Cacibupteryx and Harpactognathus were 
> excluded following Wang et al. 2009 (actually, I couldn’t follow the logic of 
> this [the exclusions, not the ‘following’] as these exclusions appear 
> completely arbitrary: for example, Cacibupteryx was scored for 36 characters 
> while “Ornithocheirus” compressirostris* was scored for only 22, but the 
> latter was included, while the former was excluded). Anyway, one might 
> predict, as Kellner’s comment implies, that the better known Darwinopterus 
> (compared to “Wukongopterus”) should now fall out as a sister group to 
> pterodactyloids. Not so. This more complete data set generated a lot more 
> trees (109980), and the strict concensus was very poorly resolved, failing, 
> for example, to recover a monophyletic Pterodactyloidea. Darwinopterus formed 
> a polytomy with many other basal forms and several pterodactyloid clades. The 
> 50% Majority Rule tree did recover a monophyletic Pterodactyoidea, but 
> “Ornithocheirus” compressirostris was located basal to Dimorphodon. 
> 
> Preliminary conclusion. The unusual character combination exhibited by 
> Darwinopterus can be used to test the behaviour of phylogenetic analyses of 
> pterosaurs. The Wang et al. 2009 phylogenetic analysis (an iteration of 
> previous Kellner data sets including: Kellner, 1996, 2003, 2004, Wang et al 
> 2005, 2008, generates poorly resolved trees in which 
> Darwinopterus/“Wukongopterus” occupy a highly anomalous position and thus 
> fail the test. Anyone who inspected the poorly resolved cladogram presented 
> by Zhou, Zhou and Schoch at SVP in Bristol this year, which was also based on 
> Kellner’s older data set and incorporated yet another example of 
> Darwinopterus (which also appears in an odd location), will have already seen 
> the same result. 
> 
> * Yes, I know this is a lonchodectid and that it does not exhibit any true 
> apomorphies of ornithocheirids, or even ornithocheiriods – don’t worry, this 
> is being dealt with elsewhere