New Azhdarchid Pterosaur Material from the Campanian Two Medicine Formation of Northwestern Montana

Lauren N. Keller, John P. Wilson, William J. Freimuth, Giulio Panasci, and Dr. David J. Varricchio, Montana State University, 100 Culbertson Hall, Bozeman, MT, 59715

Pterosaurs were an incredibly successful group of flying reptiles that existed on Earth for 150 million years. One group of pterosaurs, the azhdarchids first evolved in the Cretaceous and are arguably the most remarkable and ecologically distinct group. They are largely recognized for their enormous size, with the wingspans of some taxa reaching over ten meters in length, and a strange quadrupedal gait. Azhdarchid fossils are known globally and are unique amongst pterosaurs due to their frequent occurrence in terrestrial deposits. This unfortunately contributes to less than ideal fossilization conditions as the hollow and incredibly thin walled bones are frequently crushed or destroyed and therefore are rarely preserved at all. The Campanian Two Medicine Formation of Montana, USA has produced some pterosaur material including the type specimen of the small-bodied Montanazhdarcho. In 1979, multiple large pterosaur elements, including a humerus, radius, and carpals, were discovered at an associated site, Pterosaur Hill. These elements were identified as belonging to an indeterminate azhdarchid. Additional elements, including a large metacarpal IV, were surface collected in subsequent summers but never described. It was not until 2019 that quarrying at the site was undertaken, yielding nine new elements, including two identifiable wing-digit phalanges and a partial metacarpal. Though they have undergone minor taphonomic crushing, many of the elements are three dimensionally preserved. These new elements place this specimen among the largest and most complete of the North American azhdarchids, and includes elements not previously described for this group. This specimen predates the Maastrichtian Quetzalcoatlus and may pertain the large Campanian azhdarchid Cryodrakon. However, a comparative analysis of the distal end of metacarpal IV shows significant morphological disparity, suggesting that the Pterosaur Hill material may pertain to a new taxon. 

Additional Abstract Information

Presenter: Lauren Keller

Institution: Montana State University

Type: Poster

Subject: Geography/Geology

Status: Approved

Time and Location

Session: Poster 7
Date/Time: Tue 3:30pm-4:30pm
Session Number: 5066