The Effects of Biting and Pulling on the Forces Generated during Feeding in the Komodo Dragon (Varanus komodoensis)

In addition to biting, it has been speculated that the forces resulting from pulling on food items may also contribute to feeding success in carnivorous vertebrates. We present an in vivo analysis of both bite and pulling forces in Varanus komodoensis, the Komodo dragon, to determine how they contribute to feeding behavior. Observations of cranial modeling and behavior suggest that V. komodoensis feeds using bite force supplemented by pulling in the caudal/ventrocaudal direction. We tested these observations using force gauges/transducers to measure biting and pulling forces. Maximum bite force correlates with both body mass and total body length, likely due to increased muscle mass. Individuals showed consistent behaviors when biting, including the typical medial-caudal head rotation. Pull force correlates best with total body length, longer limbs and larger postcranial motions. None of these forces correlated well with head dimensions. When pulling, V. komodoensis use neck and limb movements that are associated with increased caudal and ventral oriented force. Measured bite force in Varanus komodoensis is similar to several previous estimations based on 3D models, but is low for its body mass relative to other vertebrates. Pull force, especially in the ventrocaudal direction, would allow individuals to hunt and deflesh with high success without the need of strong jaw adductors. In future studies, pull forces need to be considered for a complete understanding of vertebrate carnivore feeding dynamics

Dryad data

Allometric data, Principal components, and Procrustes distances for all claws

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

Research on the feeding dynamics of carnivorous dinosaurs, most of 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.Ph.D.Includes bibliographical references (p. 205-221)by Domenic C. D'Amor

Data from: Using striated tooth marks on bone to predict body size in theropod dinosaurs: a model based on feeding observations of Varanus komodoensis, the Komodo monitor

Mesozoic tooth marks on bone surfaces directly link consumers to fossil assemblage formation. Striated tooth marks are believed to form by theropod denticle contact, and attempts have been made to identify theropod consumers by comparing these striations with denticle widths of contemporaneous taxa. The purpose of this study is to test whether ziphodont theropod consumer characteristics may be accurately identified from striated tooth marks on fossil surfaces. There are three major objectives; 1) experimentally produce striated tooth marks and explain how they form; 2) determine whether body size characteristics are reflected in denticle widths; 3) determine whether denticle characters are accurately transcribed onto bone surfaces in the form of striated tooth marks. Controlled feeding trials were conducted with the dental analogue Varanus komodoensis (the Komodo monitor). Goat (Capra hircus) carcasses were introduced to captive, isolated individuals. Striated tooth marks were then identified, and striation width, number, and degree of divergence were recorded for each. Denticle widths and tooth/body size characters were taken from photographs and published accounts of both theropod and V. komodoensis skeletal material, and regressions were compared among and between the two groups. Striated marks tend to be regularly striated with a variable degree of branching, and may co-occur with scores. Striation morphology directly reflects contact between the mesial carina and bone surfaces during the rostral reorientation when defleshing. Denticle width is primarily influenced by tooth size, and correlates well with body size displaying negative allometry in both groups regardless of taxon or position. When compared, striation widths fall within or below the range of denticle widths extrapolated for similar sized V. komodoensis individuals. Striation width is directly influenced by the orientation of the carina during feeding, and may underestimate but cannot overestimate denticle width. Although body size may theoretically be estimated solely by a striated tooth mark under ideal circumstances, many caveats should be considered. These include the influence of negative allometry across taxa and throughout ontogeny, the existence of theropods with extreme denticle widths, and the potential for striations to underestimate denticle widths. This method may be useful under specific circumstances, especially for establishing a lower limit body size for potential consumers

Table S3

Dental crown morphometrics for theropod fossil specimen

Table S3

Dental crown morphometrics for theropod fossil specimen

Table S1

Crown morphometrics for Varanus komodoensis dry skull specimen

Table S1

Crown morphometrics for Varanus komodoensis dry skull specimen

Table S4

A listing of all Varanus komodoensis striated tooth marks collected

Table S4

A listing of all Varanus komodoensis striated tooth marks collected