A functional, behavioral, and taphonomic analysis of ziphodont dentition: Novel methodology for the evaluation of carnivorous dinosaur feeding paleoecology.

摘要

Research on the feeding dynamics of carnivorous dinosaurs, most which fall within Theropoda, is based on cranial/limb structure and body dimensions. Significantly less research has been concerned with dental function. Ichnological and taphonomic evidence is also used to illustrate feeding ecology, but much is without authentication through modern experimental evidence. The major goal of this dissertation is to develop novel techniques to further understand dinosaur carnivory, focusing on the group's unique ziphodont dentition. Both functionally relevant theropod tooth morphometrics and experimentation with the Komodo monitor (Varanus komodoensis), a living dental analogue, are used for the first time to draw conclusions about tooth function, feeding behavior, and tooth mark production.;When defleshing, V. komodoensis moves its rostrum so that the teeth are drawn backward through flesh to section off pieces. Tooth marks reflect this unique behavior. The majority of marks are scores produced by dragging the tooth tips across bone surfaces. Half of the marks display curvature that reflects the movement of the rostrum in an arc, and marks are frequently parallel. There is no bone crushing. Published accounts of fossil theropod marks indicate similar tooth use, but a stronger bite with less lateral rostral movement. Tooth serration widths on ziphodont teeth reflect body size in both V. komodoensis and theropods allometrically. These serrations can drag along bone surfaces, producing striations. Under ideal circumstances V. komodoensis striated tooth marks can accurately reflect the size of the consumer's serrations, and consequently its body size. The body size of a theropod consumer may therefore be determined solely from fossilized striated marks. Variability in the extent of serrations in theropod teeth is linked to the extent of contact the tooth makes with flesh. The tooth region that does not contact unmodified flesh during feeding, defined as the dead-space, does not have serrations. Highly curved teeth have the fewest serrations resulting in the largest dead space. These data also indicate that theropods may have drawn their teeth back through flesh similarly to V. komodoensis, defleshing by 'puncture cutting'. All the techniques developed here may be applied to fossil assemblages to answer questions about ziphodont paleoecology.