Microtuban altivolans (Elgin and Frey 2011) is a new basal azhdarchid pterosaur with the characteristic tiny fourth phalanx. Only the mid-section of this pterosaur is preserved, including smashed wing parts.
The scapula and coracoid are unfused and the extensor tendon process includes a large suture. Elgin and Frey (2011) considered these to be ontogenetic signals that inferred the specimen was a juvenile or sub-adult, as in archosauromorphs. Unfortunately this is false. Pterosaurs are lizards and they don’t follow archosauromorph growth patterns. The sister taxa (Fig. 1) all have similar fusion patterns and they are adults.
Elgin and Frey (2011) considered Microtuban, from the of Early Cenomanian (Late Cretaceous) of Lebanon, “the most complete pterosaur fossil discovered from Africa.” Oops. Lebanon is actually in the Middle East. Minor faux pas.
Elgin and Frey (2011) reported, “The phylogenetic placement of M. altivolans within the Azhdarchoidea [the Tapejaridae, the Thalassodromidae, the Chaoyangopteridae, and the Azhdarchidae] therefore remains uncertain.” They considered it a “thalassodromid/ chaoyangopterid.
Here, in a larger study, Microtuban nests readily at the base of the Azhdarchidae [Jidapterus through Quetzalcoatlus] and was derived from a sister to No. 42. (By the way, in the larger study Chaoyangopterus was not at all related to Thalassodromeus.) The manual phalanx proportions in Microtuban were identical to those of its azhdarchid and protoazhdarchid sisters, none of whom, no matter their size, fused the scapula to the coracoid until Quetzalcoatlus.
A Reduced Phalanx 4
While more primitive than other azhdarchids, wing phalanx 4 was relatively shorter (less than 5% of the total wing finger) in Microtuban, probably because it represents a late-surviving clade member on its own branch. The reduction of phalanx 4 is also found in Sos 2428, the flightless pterosaur, which is another Microtuban sister. I suspect that another sister, Huanhepterus, also had such a short phalanx 4, but no one I know has actually seen the post-crania.
Loss of Phalanx 4 in Other Pterosaurs?
Elgin and Frey (2011) reported that Anurognathus, Beipiaopterus and Nyctosaurus all had only three wing phalanges. This is true only for derived Nyctosaurus. Check it out.
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.
Elgin and Frey 2011. A new azhdarchoid pterosaur from the Cenomian (Late Cretaceous) of Lebanon. Swiss Journal of Geoscience. DOI 10.1007/s00015-011-0081-1