Giant Alaska pterosaur tracks indicate floating pterosaurs

Figure 1. Pterosaur tracks from Alaska. Note the lack of pedal tracks and the large size of the manus tracks.

Figure 1. Pterosaur tracks from Alaska. Note the lack of pedal tracks and the large size of the manus tracks.

Figure 2. Closeup of a giant pterosaur manus track. Digits identified.

Figure 2. Closeup of a giant pterosaur manus track. Digits identified.

A recent paper ( ) described giant Late Cretaceous pterosaur tracks from the far north in Alaska. These are likely made by large azhdarchids, like Quetzalcoatlus.

At 18 centimeters long by 6 centimeters wide, the bigger pterosaur tracks are “very large” compared to others that have been reported, Fiorillo’s team says.

The more diminutive set of prints, meanwhile, was only about one-fourth as large — about 6 centimeters by 4 centimeters.

Manus only tracks were likely produced by floating and poling pterosaurs as we talked about earlier with Tapejara. Here the size and proportions of the manus tracks, along with the location and time period all point toward giant azhdarchids.

Figure 1. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks.

Figure 3. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks.

It is important to appreciate the great size of the pterosaurs that made such large manus tracks, especially so since the fingers that made the impressions are among the smallest parts on the pterosaur itself.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 4. Quetzalcoatlus specimens to scale. Here digit 3 is approximately 18 cm long, matching the size of the track. The manus of Quetzalcoatlus is poorly known. These are based on Zhejiangopterus and Azhdarcho. The second finger could have been shorter to match the tracks. The ability of digit 3 to rotate posteriorly harkens back to the lepidosaur ancestry of pterosaurs.

Manual 3.1 of Azhdarcho (Fig. 4) shows how that digit was able to bend posteriorly. Like most lizards, the fingers were rather free to rotate on bulbous articular surfaces.

Figure 2. Manual 3.1 for Azhdarcho. Note the bulbous proximal portion.

Figure 5. Manual 3.1 for Azhdarcho. Note the bulbous proximal portion enabling posterior bending.

 

References
Fiorillo AR et al. 2009. A pterosaur manus track from Denali National Park, Alasak range, Alaska, United States. Palaios 24: 466-472.

Fiorillo AR et al. 2014. Pterosaur tracks from the Lower Cantwell Formation (Campanian–Maastrichtian) of Denali National Park, Alaska, USA, with comments about landscape heterogeneity and habit preference. Historical Biology DOI:10.1080/08912963.2014.933213

Online report.

 

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