Hydrodynamic behaviors of pachycephalosaurid domes in controlled fluvial settings: A case study in experimental dinosaur taphonomy

摘要

The hydrodynamic behaviors of isolated dinosaur bones have been largely overlooked in the paleontological literature. Investigations into the hydrodynamic properties of dinosaur remains with unique taphonomic signatures, such as pachycephalosaurid frontoparietal domes, have the potential to aid in the interpretation of preservation for skeletal elements for which modern analogues are not available. For this study, a series of transport experiments were conducted to assess the entrainment velocities and settling orientations of a collection of pachycephalosaurid specimens. Casts of four pachycephalosaurid frontoparietal domes and skulls were composed of a urethane resin with a comparable average density to compact and cancellous bone, and placed in a flume with manual velocity control. Data were recorded for competent velocity, transport distance, and settling orientations upon resting and burial of specimens for 35 trials per cast. Though specimens vary considerably in mass, the results suggest specimen shape has a greater influence on transport and hydrodynamic behavior than size; significantly lower velocities are required to transport complete skulls than isolated domes. Resting and burial orientations of specimens vary significantly for domes and complete skulls. The highly variable transport velocities and settling orientations of pachycephalosaurid crania offer insight into pachycephalosaurid taphonomy and illustrate the importance of future taphonomic studies on large fossil vertebrate remains.