Recognition of paleogastroliths from the Lower Cretaceous Cedar Mountain Formation, Utah using a scanning electron microscope

摘要

Paleogastroliths, as defined in this study, are stomach stones associated exclusively with extinct animals. Definitive recognition of paleogastroliths is problematic and controversial. Polished, rounded stones found within skeletal remains of dinosaurs and plesiosaurs are the strongest evidence. This study examined intraskeletal and proposed paleogastroliths using a scanning electron microscope (SEM) to determine if any defining surface textures occur. Paleogastroliths associated with the skeletal remains of Seismosaurus hallorum, possible paleogastroliths from the Lower Cretaceous Cedar Mountain Formation, and other well-polished stones were obtained. Most stones were composed of either quartzite or chert and were examined with a SEM at magnifications ranging from 100 to 400. All of the cherty Seismosaurus hallorum stones contained sets of parallel to sub-parallel, curved polish grooves that in places crosscut one another. These grooves are inferred to have formed as the result of small particles lodged in the stomach muscles interacting with the stones due to muscle movement. The distinctive surface textures noted on the cherty Seismosaurus hallorum paleogastroliths are similar to those seen on the cherty possible paleogastroliths from the Cedar Mountain Formation. Therefore, the geologic occurrence combined with the microscopic surface texture supports the interpretation that these stones are paleogastroliths.