When Darwinopterus was first described (Lü et al. 2010) it was promoted as the transitional taxon uniting basal long-tailed pterosaurs with derived “pterodactyloid” pterosaurs, those with a united naris and antorbital fenestra. The Monofenestrata was a clade invented to include Darwinopterus and its kin along with traditional “pterodactyloids.” It has come to be accepted among pterosaur workers.
Unfortunately the original phylogenetic analysis (Lü et al. 2010) was poorly resolved, especially so at the transition point.
A larger pterosaur tree, including many more taxa, resolved the issue and found that Darwinopterus and kin nested with Pterorhynchus and this clade became extinct afterwards, leading to no other so-called “pterodactyloids.” In fact there were four convergent origins to the various “pterodactyloid” clades, not just one, as demonstrated by the large pterosaur study. These were derived from Dorygnathus and Scaphognathus (itself derived from Dorygnathus, too).
So, by this definition, the Monofenestrata is polyphyletic (not monophyletic) and therefore it has no value.
The enlargement of the skull in the Darwinopterus/Pterorhynchus clade along with the reduction and disappearance of the naris was convergent with the other four “pterodactyloid”-grade clades. Hence the confusion built on hope, perhaps for fame or resolution, not a comprehensive fully-resolved phylogenetic analysis.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
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.