PTERANODON PRESERVATION IN THE LATE CRETACEOUS NIOBRARA CHALK OF WESTERN KANSAS

Pteranodon lived along the coast of the Western Interior Seaway, which covered part of North America during the Late Cretaceous. In all, approximately 1200 specimens of Pteranodon have been found across the seaway, but little is known about how they were preserved in Kansas’s Niobrara Formation. For this project, the taphonomic condition of 81 Pteranodon specimens was examined at the University of Kansas Natural History Museum in order to find out about the conditions they were preserved in. All specimens are from the Smoky Hill Chalk Member of the Niobrara Formation (upper Coniacian to lower Campanian) in western Kansas. Information recorded includes species, bones present, locality, lithology, associated fossils, articulation, sorting, fracturing, weathering, polish, abrasion, scratch and tooth marks, distortion, bioturbation, and corrosion. Taphonomic features were separated out by those that formed before burial and those that formed after burial. The pre-burial taphonomic data suggests that conditions were ideal for preservation. A lack of polish, corrosion or evidence of bioturbation suggests that there was a low-energy environment with a neutral pH and soft sediment. Most specimens were inarticulated and poorly to moderately sorted, which indicate either scavenging, bottom currents, or decomposition separated skeletons on the seafloor. Although scavenging marks were rare, it is thought that scavenging was common due to the rarity of bones from or close to the main bodies of the Pteranodon specimens. The majority of bones in specimens came from wings. Wing bones may have been held together by the patagium (wing membrane) or ignored by scavengers due to a preference for parts of the body with more meat. Skulls were rare, which could be because they tended to separate from the rest of the body while sinking to the seafloor, since they were heavy relative to other parts of the body. Taphonomic features that formed after burial indicate weathering and overlying strata also affected the condition of the bones. The specimens most commonly had no to little modern weathering, were very fractured, had little abrasion, and had significant compression due to the bones being hollow. In sum, Pteranodon preserved well in the Niobrara due to quick burial in soft sediment in a low-energy environment with low oxygen and a neutral pH.