Abstract
Because overall cranial morphology-biomechanics linkage in carnivorans is significantly influenced by both feeding and non-feeding ecological variables, whole-skull mechanical performance measures may be less sensitive to feeding ecology than regional characteristics within the skull. The temporomandibular joint could be one regional characteristic that is highly sensitive to feeding ecology considering that this joint is used in prey capture, food processing, and experiences compressive loading during mastication. Through 3D model construction, 3D printing, and compression tests, morphological and mechanical performance measures were determined for the temporomandibular joint trabecular bone structure of 40 species representative of the phylogenetic and ecology diversity of Carnivora. Remarkably, the results indicate that relative fill volume, relative structural complexity, elastic modulus, and relative maximum compressive strength of trabecular bone structure are not significantly related to phylogeny or ecology. The results reveal that morphological and mechanical performance attributes of trabecular bone structure are primarily influenced by body size, and that positive centroid size allometry and positive body mass allometry are present for structural complexity. The lack of feeding ecological signal in dorso-ventral compressive loading of temporomandibular joint models indicates that carnivoran temporomandibular joint trabecular structures may not undergo significant differential remodeling as an evolutionary response to different mechanically demanding feeding tasks.
Highlights
It has been assumed that cranial structure-biomechanics relationships are primarily influenced by feeding ecology in carnivorans, but recent results from geometric morphometrics and finite element analysis suggest that carnivoran cranial morphology is related to both feeding and non-feeding variables [1]
The carnivoran skull must meet myriad functional demands besides prey capture and feeding, which may suggest that more suitable attributes for evaluating feeding ecology are mechanical performance measures from specific anatomical structures that are directly associated with prey capture and food processing
Upon consideration that the temporomandibular joint is involved in prey capture and food processing, that the mandibular condyle experiences compressive loading during mastication, Carnivoran jaw joint trabecular bone structural properties and that biomechanical feedback appears to influence mandibular condyle biomineralization levels and coordination of oral tissue development, the morphology and mechanical performance of this structure appeared to have great potential to provide engineering-based measures of feeding ecology [2,3,4,5]
Summary
It has been assumed that cranial structure-biomechanics relationships are primarily influenced by feeding ecology in carnivorans, but recent results from geometric morphometrics and finite element analysis suggest that carnivoran cranial morphology is related to both feeding and non-feeding variables [1]. The carnivoran skull must meet myriad functional demands besides prey capture and feeding, which may suggest that more suitable attributes for evaluating feeding ecology are mechanical performance measures from specific anatomical structures (e.g., the temporomandibular joint, or TMJ) that are directly associated with prey capture and food processing. The mandibular condyle of the temporomandibular joint in mammals is likely to be under selection involving masticatory mechanical loads, given that previous research utilizing rosette strain gages in Sus (domestic pigs) shows that the mandibular condyle is subject to loading during mastication and that these forces are mostly compressive [2]. Upon consideration that the study of human mandibular condyles shows that trabecular bone experiences much greater ranges of stresses and strains than does the cortical bone [5], temporomandibular joint trabecular bone structure might offer a useful structure-performance measure for assessing feeding ecology
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