Abstract: Gastroliths, Rigor Mortis, and Taphonomy of the Seismosaurus Site
David D. Gillette
As the longest (150 ft) and perhaps the largest (50-100 tons) of the supergiant dinosaurs, Seismosaurus hallorum represents the pinnacle of success of the massive sauropods that reached their greatest diversity in the Jurassic and then suffered near extinction at the Jurassic-Cretaceous boundary, the sauropod crisis. Feeding habits of the sauropods may have been directly tied to their nearly total demise at the end of the Jurassic, when flowering plants emerged to dominate the landscape. Sauropods probably depended on rough forage from conifers, cycads, and ferns for food. Some have postulated that the sauropods used stomach stones for pulverizing foodstuffs. The Seismosaurus excavation indicates that sauropods had two specialized chambers in the digestive tract: an anterior rop and a posterior gizzard.
The partially articulated skeleton of Seismosaurus hallorum from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) of central New Mexico was buried in coarse fluvial sand. The skeleton was excavated with the assistance of experimental technology used to see into the ground: ground penetrating radar, acoustic diffraction tomography, scintillation counting, and proton free-precision magnetometry. The complicated taphonomic history prior to burial includes rigor mortis, secondary displacement of parts of the skeleton by fluvial processes, scattering of more than 240 gastroliths, and scavenging by a carnivore. A plausible, though improbable, cause of death can be discerned from this forensic evidence.
AAPG Search and Discovery Article #90985©1994-1995 AAPG Distinguished Lecture