FLUVIAL TRANSPORT POTENTIAL OF ARCHOSAUR TEETH: A PRELIMINARY INVESTIGATION IN SHED TOOTH TAPHONOMY

The rate of tooth replacement in dinosaurs has been well-studied as a part of paleobiology. The tooth replacement rates for sauropods have been determined to be very rapid, replacing teeth in as little as 30 days. Theropods have a considerably lower replacement rate, replacing teeth over a nine-month span. In the Late Jurassic Morrison formation the shed teeth of large theropods such as Allosaurus are more abundant than the shed teeth of sauropods. However, this is at odds with the relatively higher abundance of sauropod skeletal remains. While this disparity may be due to ecological or behavioral influences, such as predator/prey ratios or migratory strategies, taphonomic processes, such as fluvial transport potential, may also be influential. To investigate taphonomic influences on shed tooth abundances, an experiment was designed to test the fluvial transport potential of shed theropod and sauropod teeth. Teeth of Alligator mississipiensis were utilized to model dinosaur teeth; shed crowns of A. mississippiensis represented conical-shaped theropod teeth, and full teeth were used to model peg-shaped teeth of diplodocids. Teeth were placed in a recirculating flume parallel to flow and measured for entrainment velocity and relative transport distance prior to burial. Preliminary results show a significant difference in the entrainment velocities of shed theropod and diplodocid teeth. Sauropod teeth exhibit greater relative transport distances with increases in flow velocity, while theropod teeth show variable relative transport distances and entrainment velocities; theropod teeth are transported farthest at a relatively low velocity (14.2 cm/sec). Based on these preliminary data, distinct differences are expected in the preservation conditions and abundances of shed teeth; sauropod teeth are expected to be more abundant in the fossil record, and perhaps found as lag clusters while theropod teeth are expected to be in lower relative abundance and exhibit abrasion and fracturing due to prolonged transport. Further investigations are planned to expand flume experiments with resin casts of larger teeth of Allosaurus, Diplodocus, and Camarasaurus to more accurately model tooth shape.