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Darwinopterus: 5 specimens in phylogenetic analysis – part 1
Earlier we looked at Darwinopterus, of which several specimens (Figs. 1,2) are now known. When the female with the associated egg was found (Lü et al. 2011a) they proposed that some of the differences (pelvis shape, rostral crest, size) could be attributed to gender.
We learned earlier that this would be a unique situation among pterosaurs as all other such candidates for this difference do not indicate gender, but phylogeny when placed under analysis (small crests are derived from no crests and small crests give rise to large crests, for instance). What Lü et al. considered a deep ischium in the female was found to be a deep prepubis here.
Like Pteranodon, Rhamphorhynchus, Pterodactylus, Germanodactylus and other genera, I added the five specimens attributed to Darwinopterus (Fig. 1) to the large pterosaur tree to see how they might be related to one another in a first ever phylogenetic analysis of this genus (Fig. 2).
Figure 1. Click to enlarge. The five specimens of Darwinopterus to scale and in phylogenetic order preceded by six more primitive taxa. The ZMNH 8802 specimen is a female associated with an egg. The others genders shown are guesses by Lü et al. 2011a. Note the skull did not elongate, it actually shrank in the vertical dimension, probably reducing its weight. The female is crestless because it is the most primitive of the five known Darwinopterus specimens. The odds that the remaining four specimens are all males is relatively small. The odd throat sac of Pterorhynchus may represent a normal throat ripped away from its base.
Figure 2. Subset of the large pterosaur tree showing relationships among Darwinopterus and its predecessors among the Wukongopteridae and their predecessors.
To give some perspective
Jianchangnathus, at the base of this subset of the large pterosaur tree, also nested between basal Dorygnathus and Scaphognathus. No taxa succeed Darwinopterus. It was a sterile lineage, not a transitional taxon.
Note the very small naris and relatively large skull on Jianchangnathus. More derived taxa, including Darwinopterus, had a skull that was just as long, just not as tall, thereby reducing its weight. So this clade did not have a longer skull than sister taxa.
All more derived taxa, including Darwinopterus, also had a reduced to absent naris. So this is the genesis of that trait.
The long neck of wukongopterids also had its genesis in more basal taxa, like the PMOL specimen attributed to Changchengopterus by Zhou and Shoch 2011.
Earlier we noted the relationship of Pterorhynchus to the wukongopterids. And recently we noted that the new specimen referred to Changchengopterus (Zhou and Schoch 2011) actually nests at the base of the Wukonopteridae, far from the the holotype Changchengopterus, which is half the size.
Kunpengopterus now has a sister taxon in Archaeoistiodactylus (Lü and Fucha 2010) which Martill and Etches (2012) correctly referred to this clade.
Tomorrow we’ll look at the five specimens of Darwinopterus a little more closely.
References
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B (DOI 10.1098/rspb.2009.1603.)
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011a. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323
Lü J, Xu L, Chang H and Zhang X 2011b. A new darwinopterid pterosaur from the Middle Jurassic of Western Liaoning, northeastern China and its ecological implicaitions. Acta Geologica Sinica 85: 507-514.
Lü J-C and Fucha X-H 2010. A new pterosaur (Pterosauria) from Middle Jurassic Tiaojishan Formation of western Liaoning, China. Global Geology 13 (3/4): 113–118. doi:10.3969/j.issn.1673-9736.2010.03/04.01.
Martill DM and Etches E 2012. A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England. Acta Palaeontologica Polonica. in press. doi:10.4202/app.2011.0071.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi & Rodrigues T 2010. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062.
Wang X-L, Kellner AWA, Jiang S-S, Cheng X, Meng X and Rodriques T 2014. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências (2010) 82(4): 1045-1062.
Zhou C-F and Schoch RR 2011. New material of the non-pterodactyloid pterosaur Changchengopterus pani LÜ, 2009 from the Late Jurassic Tiaojishan Formation of western Liaoning. N. Jb. Geol. Paläont. Abh. 260/3, 265–275 published online March 2011.
wiki/Kunpengopterus
wiki/Darwinopterus
Source: http://pterosaurheresies.wordpress.com/2014/02/06/darwinopterus-5-specimens-in-phylogenetic-analysis-part-1/
