Main » 2008 » September » 11 » PROBABLE GUT CONTENTS WITHIN A SPECIMEN OF BRACHYLOPHOSAURUS CANADENSIS (DINOSAURIA: HADROSAURIDAE) FROM THE UPPER CRETACEOUS FROM MONTANA
PROBABLE GUT CONTENTS WITHIN A SPECIMEN OF BRACHYLOPHOSAURUS CANADENSIS (DINOSAURIA: HADROSAURIDAE) FROM THE UPPER CRETACEOUS FROM MONTANA
An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canadensis, from the Judith River Formation near Malta, Montana, contains abundant plant fragments concentrated within the body cavity. We examined the taphonomy of the carcass and analyzed the gut-region material to test whether the organic remains represent fossilized gut contents. The dinosaur was buried in a fluvial channel setting, and the excellent articulation, integument impressions, and lack of scavenging indicate rapid burial. The organic material occupies a volume of at least 5750 cm3, and comparable material is not found outside the carcass. The carcass contents include 63% clay, 16% undetermined matrix, 12% organic matter, and 9% larger inorganic clasts—mostly 50–100 m quartz grains. Most of the organics appear to be mm-scale leaf fragments. The most parsimonious explanation for the presence and composition of the gut-region material is that much of the plant fossils represent reworked brachylophosaur ingesta influenced by flowing water that entered through openings in the carcass and introduced clay. The evidence strongly suggests that the hadrosaurid ate significant quantities of leaves and processed them into small pieces. This study provides baseline information for analyzing other cases of putative gut contents in herbivorous dinosaurs.
Brachylophosaur specimen JRF 115H and its discovery site. A) JRF 115H in situ. Arrow indicates block of caudal vertebrae separated from the rest of the specimen by a small wash. Matrix is fine-grained sandstone. Black bar is 25 cm long. Photograph taken by Mark Thompson. B) Skeletal map of JRF 115H, made during excavation by Greg Wenzel. Each square is 25 cm long on a side. C) JRF 115H after preparation to indurated matrix with person for scale. Indurated matrix (white arrow) is more yellowish in color and more indurated than other remaining matrix (black arrow).