title: Cranial biomechanics underpins high sauropod diversity in resource-poor environments.
abstract: High megaherbivore species richness is documented in both fossil and contemporary ecosystems despite their high individual energy requirements. An extreme example of this is the Late Jurassic Morrison Formation, which was dominated by sauropod dinosaurs, the largest known terrestrial vertebrates. High sauropod diversity within the resource-limited Morrison is paradoxical, but might be explicable through sophisticated resource partitioning. This hypothesis was tested through finite-element analysis of the crania of the Morrison taxa Camarasaurus and Diplodocus. Results demonstrate divergent specialization, with Camarasaurus capable of exerting and accommodating greater bite forces than Diplodocus, permitting consumption of harder food items. Analysis of craniodental biomechanical characters taken from 35 sauropod taxa demonstrates a functional dichotomy in terms of bite force, cranial robustness and occlusal relationships yielding two polyphyletic functional 'grades'. Morrison taxa are widely distributed within and between these two morphotypes, reflecting distinctive foraging specializations that formed a biomechanical basis for niche partitioning between them. This partitioning, coupled with benefits associated with large body size, would have enabled the high sauropod diversities present in the Morrison Formation. Further, this provides insight into the mechanisms responsible for supporting the high diversities of large megaherbivores observed in other Mesozoic and Cenozoic communities, particularly those occurring in resource-limited environments.
authors.affiliation: School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TP, UK Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5DB, UK gldjb@bristol.ac.uk.
authors.forename: David J
authors.initials: DJ
authors.lastname: Button
authors.affiliation: School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TP, UK.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Rayfield
authors.affiliation: Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5DB, UK.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Barrett
mesh_terms: D000818:Animals; D044822:Biodiversity; D001696:Biomechanical Phenomena; D025061:Dinosaurs / Q000033:anatomy & histology* / Q000502:physiology*; D017753:Ecosystem; D020342:Finite Element Analysis; D005580:Fossils / Q000033:anatomy & histology; D012886:Skull / Q000033:anatomy & histology*
keywords: Morrison Formation; biomechanics; finite-element analysis; megaherbivores; niche partitioning; sauropod