GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 84-48
Presentation Time: 9:00 AM-5:30 PM


SNYDER, Keith, Biology Department, Southern Adventist University, Collegedale, TN 37315, MCLAIN, Matthew A., Department of Biological and Physical Sciences, The Master’s University, 21726 Placerita Canyon Road, Santa Clarita, CA 91321 and CHADWICK, Arthur V., Geology, Southwestern Adventist University, 100 Magnolia, Keene, TX 76059,

In the Upper Cretaceous deposits of western North America, monodominant bonebeds consisting of hadrosaurids or ceratopsids are relatively common, as are multitaxic microvertebrate bonebeds, but multitaxic macrovertebrate bonebeds are uncommon. In 2014, we discovered a roughly 2-meter-long (snout to frill edge) Triceratops skull, and further excavation over the next three summers revealed a peculiar multitaxic macrovertebrate assemblage in the Lance Formation of eastern Wyoming. In addition to a Triceratops, we uncovered remains from the ornithischians Thescelosaurus and Edmontosaurus, and the caenagnathid theropod Anzu. In each case, a single individual is represented, and the remains are slightly disarticulated to disarticulated, but associated. Other taxa are represented in the bonebed only by isolated elements. In addition to its skull, the Triceratops individual is represented by its pubis, femur, tibia, metatarsals, and phalanges. Over 100 bones have been recovered from the Thescelosaurus specimen with the skull, vertebrae, pelvic girdle, and hind limbs well represented. About 70 caudal vertebrae from the Edmontosaurus individual were split between three separate articulated sections, and they are associated with disarticulated hip and limb elements of the same individual. Associated Anzu material includes a tibia, fibula, astragalus, metatarsals, radius, and caudal vertebrae. The remains of all four individuals are in close proximity, overlapping or partially overlapping. These specimens present a rare picture of dinosaurian diversity at a single macrovertebrate site. Why these four individuals – each of a different species – were buried together is a mystery, but we will continue to excavate the site and study its sedimentology to gain a better understanding of the assemblage’s taphonomic history.