THE TAPHONOMY OF A CHASMOSAURINE DINOSAUR BONE BED FROM THE JAVELINA FORMATION (MAASTRICHTIAN) OF BIG BEND NATIONAL PARK, TEXAS

Taphonomic and sedimentologic attributes of a bone bed located in the Javelina Formation (late Maastrichtian) of Big Bend National Park, Texas, suggest a monospecific chasmosaurine dinosaur (cf. Torosaurus utahensis, TMM 41361) assemblage. This bone bed represents the only monospecific remains of chasmosaurines from the southwestern portion of North America. The only other known chasmosaurine bone beds are from the Aguja Formation of Big Bend National Park (Chasmosaurus mariscalensis) and from the Horseshoe Canyon Formation of Alberta, Canada (Anchiceratops ornatus). Therefore the data provided by this third known bone bed may help yield new information regarding chasmosaurine dinosaurs and their environments.

TMM 41361 is dominated by large appendicular and girdle elements. These fossils occur in the upper portion of an abandoned stream channel deposit. Evidence, including the absence of skulls and smaller elements, including vertebra and ribs, indicates a renewal in channel flow. This caused an alignment of the large immobile bones by the current, burying them in a dark, organic rich mud. These associated, parautochthonous remains are constrained to a single horizon. Remains indicate two adults and a juvenile are preserved at TMM 41361. The bones show evidence of mild weathering, breakage, plastic deformation, and decay of poorly ossified parts, suggesting a brief exposure following death. There is no evidence of predation or scavenging on the preserved remains.