The Family Tree of the Pterosauria 13 – The Base of the Pteranodontia

We just looked at the various crested descendants of Germanodactylus cristatus, the Dsungaripteridae, the Shenzhoupteridae and the Tapejaridae (part 1 and part 2). Here we look at another, taller specimen of Germanodactylus with a more typical shoulder joint  that was not at the bottom of the torso. This taller specimen is private and undescribed, but assigned the number SMNK-PAL 6592 during its loan to the Stuttgart Museum. It was derived from a sister to Elanodactylus and basal to the most iconic of all pterosaurus, Pteranodon along with Nyctosaurus and Eopteranodon.

Protopteranodontia

Figure 1. The Protopteranodontia. Led by a specimen referred to Germanodactylus cristatus and Elanodactylus, tiny No. 13 is basal to the Pteranodontia, including Eopteranodon, Nyctosaurus (including Muzquizopteryx and Pteranodon.

Elanodactylus
Originally considered close to azhdarchids and ctenochasmatids, the two specimens of Elanodactylus are known principally from complete wings much larger than those of other Germanodactylids. The metacarpus was relatively smaller. The proximal wing phalanx was shorter than the second wing phalanx. Fingers 1-3 were robust.

The SMNK (private) specimen referred to Germanodactylus cristatus
Overall larger and distinct from the BMM specimen, in the  SMNK Germanodactylus the anterior tooth was larger and elevated to the directly anterior orientation creating a sharper snout that was longer than the mandible. The rostral margin was straight and terminated in a small posteriorly-oriented parietal crest. The antorbital fenestra was larger. The rostrum was deeper. The sternal complex was larger with sharper corners. The deltopectoral crest was displaced distally, away from the proximal articular surface. The distal humerus was expanded. The pelvis was longer. The femur was much longer, subequal to the tibia. No three unguals were aligned. Manual 1.1 was longer and m2.1 was shorter. The skull is a close match to that of the most primitive Pteranodon, P. occidentalis.

B St 1878 VI 1 (No. 13)
Overall much smaller than and distinct from SMNK-PAL 6592, the skull of No. 13 was relatively smaller. The orbit was larger and the antorbital fenestra was smaller. The lacrimal was larger. The mandibular symphysis was longer and slightly more deeply keeled. The cervicals were more gracile. The sacrals were shorter. The caudals were smaller. The humerus was smaller. The distal wing elements were shorter. Fingers I-IV were more robust and shorter. The pelvis was shorter with a larger space between the pubis and ischium. The hind limb was shorter and more robust. Metatarsal III was as long as mt II. Pedal unguals II-IV were aligned. Pedal 2.1 was shorter than p2.2. The skull of No. 13 nests at the base of Muzquizopteryx plus  Eopteranodon.

Eopteranodon and Eoazhdarcho
Overall much larger than No. 13, the mandible of Eopteranodon was reported as toothless and crested. The scapula was longer than the coracoid. The humerus was tongue-shaped and more robust. The metatacarpals were longer than the ulna/radius. Fingers 1-3 were more gracile. The proportions of the wing phalanges are unchanged relative to the rest of the forelimb. The pubis included a posterior process. The ischium was not so expanded distally. The anterior process of the posterior ilium was angled dorsally. The prepubis was shallower. The femur was longer. The tibia was relatively longer, in keeping with the metacarpus and manual 4.1. The pes was relatively smaller. It is likely that Eopteranodon and Eoazhdarcho are congeneric. Data with greater resolution should be able to solve this problem.

The great length of the metacarpus in Muzquizopteryx/Nyctosaurus may be inherited from the long metacarpus of Eopteranodon, but Muzquizopteryx/Nyctosaurus had shorter legs and a shorter neck.

Bakonydraco galacz (Osi, Weishampel and Jianu 2005) Santonian ~84 mya, Late Cretaceous, was considered an azhdarchid, but it shares few traits with those flat-jawed pterosaurs. Known form a mandible and perhaps some cervicals found nearby, Bakonydraco is more closely allied with Eopteranodon and Eoazhdarcho, which are unrelated to azhdarchids.

Muzquizopteryx and Nyctosaurus
We’ll discuss this lineage next.

Pteranodon
And the day after that.

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.

References:
Lü J-C and Zhang B-K 2005. New pterodactyloid pterosaur from the Yixian Formation of western Liaoning. Geological Review 51 (4): 458–462.
Lü J-C and Ji Q 2006. Preliminary results of a phylogenetic analysis of the pterosaurs from western Liaoning and surrounding area. Journal of the Paleontological Society of Korea 22 (1): 239–261.
Lü J, Unwin DM, Xu L and Zhang X 2008. A new azhdarchoid pterosaur from the Lower Cretaceous of China and its implications for pterosaur phylogeny and evolution. Naturwissenschaften,
Ösi A, Weishampel DB and Jianu CM 2005. First evidence of azhdarchid pterosaurs from the Late Cretaceous of Hungary. Acta Palaeontologica Polonica 50 (4): 777–787. online pdf
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Zittel KA 1882.  Über Flugsaurier aus dem lithographischen Schiefer Bayerns. Palaeontographica 24: 47-81.

wiki/Eopteranodon
wiki/Bakonydraco
wiki/Muzquizopteryx
wiki/Pteranodon

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