Aurorazhdarcho – Unfortunately, Not Related to Azhdarcho.

A recent paper by Frey, Meyer and Tischlinger (2011) reported on a pterosaur that has been known for several years, but only now published and given a name, Aurorazhdarcho. The authors erected a new family, the Protazhdarchidae and attributed the specimen to the Azhdarchoidea. Here, along with Wellnhofer’s no. 13,  Eopteranodon and Eoazhdarcho, Auroazhdarcho nests at the base of Pteranodon + Nyctosaurus, far from any azhdarchids despite overall appearances. The details tell another story.

Convergence Again
Below we can see members of the Azhdarchidae (Fig. 1) and the Eopteranodon clade (Fig. 2) that includes Aurorazhdarcho. Keys to making this nesting were the distinct proportions of the manual and pedal elements. The prepubes were virtually fused at the midline in Auroazhdarcho, as in sister taxa.

The Azhdarchidae.

Figure 1. The Azhdarchidae. Click to enlarge. Note the resemblances to Auroazhdarcho, all by convergence.

Golden Flakes in UV
Apparently without a skull and cervicals, Aurorazhdarcho preserves a faint skull-like patch of golden flakes seen in ultraviolet light. In Figure 2, the abstract tracing above the reconstruction of Aurorazhdarcho was taken from this amorphous area. The gray skull and cervicals in Figure 2 are a best guess reconstruction. Apparent rows of no. 13-like teeth are barely visible, but let’s not put too much stock in those. I don’t know what to make of all the curved lines, including a highly curved mandible. Did the fossil soften up before burial? The rest of it did not. Did they get washed away before burial, leaving only drifting impressions? Good question. No answer. The rest of the fossil was swirled a bit.

Figure 2. Left to right, Eopteranodon, Wellnhofer's No. 13 and Aurorazhdarcho, sisters that nest far from the Azhdarchidae.

Figure 2. Left to right, Eopteranodon, Wellnhofer’s No. 13 and Aurorazhdarcho, sisters that nest far from the Azhdarchidae.

Missing Pedal Phalanges?
The authors did not make mention of the missing disc-like pedal phalanges (p3.2, p4.2, p4.3) typically found in pterosaurs of this grade, nor did they illustrate them. If the disc-like phalanges were fused to the larger phalanges, or had just disappeared (as in higher cynodonts), that would be news that was apparently overlooked.

The Skinniest Pterosaur?
Aurorazhdarcho may have had the skinniest legs of all pterosaurs (but see Rhaeticodactylus for more gracile wings).  Compared to its sisters (Fig. 2) Aurorazhdarcho was more gracile in the wings as well.

The Sternal Complex
The sternal complex is quite large and broad in Aurorazhdarcho and its sisters. Not so in Quetzalcoatlus and its azhdarchid sisters back to the Jurassic taxa where the non-azhdarchid sisters to the azhdarchidsHuanhepterus, no. 44, no. 42 and no. 57 have a large sternal complex.

Male or Female? Juvenile or Mature?
Frey, Meyer and Tischlinger (2011) reported, “The partial fusion of the glenoideal suture of the scapulocoracoid and the near complete co-ossification of the olecranon process with the basal wing finger phalanx suggests a late juvenile or subadult individual (cf. Bennett 1993; Frey and Martill 1998).”

Figure 3. The faintest impressions of a skull were found by the original authors and colorized here.

Figure 3. The faintest impressions of a skull were found by the original authors and colorized here. I think the tan element is a palatal element. Hard to say.

Unfortunately, these are phylogenetic characters, as we learned earlier. As lizards, pterosaurs don’t follow archosaur bone growth patterns (Maisano 2004).

Frey, Meyer and Tischlinger (2011) also reported, “We suggest here that a ventrally open pelvis lacking a puboischiadic symphysis would be indicative for a female because of the wide pelvic apperture would serve as an egg passage (Unwin 2006). Those pterosauria with a tightly fused puboischiadic symphysis and a narrow pelvic aperture like NMB Sh 110 are likely to have been males.”

Unfortunately the ventrally open/closed pelvis is also a phylogenetic character. The symphysis is a trait shared with sisters. Fusion of the pubis and ischium occurs in Eopteranodon (Fig. 2).

Aurorazhdarcho was a Jurassic sister to Wellnhofer’s (1970) no. 13 and the Early Cretaceous sisters Eoazhdarcho and Eopteranodon. Jurassic sisters to the Azhdarchidae include Wellnhofer’s no. 42 and no. 44, just as skinny and crane-like.

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.

Frey E, Meyer CA and Tischlinger H 2011. The oldest azhdarchoid pterosaur from the Late Jurassic Solnhofen Limestone (Early Tithonian) of Southern Germany. Swiss Journal of Geosciences, (advance online publication) doi:10.1007/s00015-011-0073-1

Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.


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