New Mexico Geological Society Annual Spring Meeting — Abstracts

UNM (University of New Mexico) FKK-200 is a partial skeleton of a hadrosaurian dinosaur, cf. Edmontosaurus sp., collected in the NE1/4, NW1/4, NW1/4, sec. 7. T24N, R11W, San Juan County, New Mexico from fine-grained, clayey, white to pinkish-gray sandstone of the
Naashoibito Member of the Kirtland Shale, 6.8-m-below the Naashoibito-Ojo Alamo Sandstone contact. Longitudinal fractures on some bones of UNM FKK-200 ("Stage I Weathering"), the skeletal elements present (girdles, sacrum, ribs) and their degree of disarticulation in the sediment suggest less than three years of subaerial weathering followed by burial of an incomplete, though fairly coherent, carcass in a stream channel. The probable occurrence of Edmontosaurus documented by UNM FKK-200 is consistent with assignment of a Lancian age to the Naashoibito.

The matrix within the ribs of UNM FKK-200 contained a complete adult body-chamber of the scaphite Scaphites whitfieldi (UNM FKK-201;
identification confirmed by W.A. Cobban, written comm., 1984). S. whitfieldi, a Turonian scaphite typically found in the Juana Lopez Member and D-Cross Tongue of the Mancos Shale in New Mexico, must be reworked in the Naashoibito because this unit is demonstrably
Maastrichtian and terrestrial in origin. Two possibilities are: 1. The hadrosaur ingested a fossil scaphite while feeding, possibly to serve as a gastrolith. 2. Part of the source terrain of the Naashoibito exposed Turonian marine rocks from which the scaphite was removed and redeposited by streams.