title: Temporal and phylogenetic evolution of the sauropod dinosaur body plan.
abstract: The colossal size and body plan of sauropod dinosaurs are unparalleled in terrestrial vertebrates. However, to date, there have been only limited attempts to examine temporal and phylogenetic patterns in the sauropod bauplan. Here, we combine three-dimensional computational models with phylogenetic reconstructions to quantify the evolution of whole-body shape and body segment properties across the sauropod radiation. Limitations associated with the absence of soft tissue preservation in fossils result in large error bars about mean absolute body shape predictions. However, applying any consistent skeleton : body volume ratio to all taxa does yield changes in body shape that appear concurrent with major macroevolutionary events in sauropod history. A caudad shift in centre-of-mass (CoM) in Middle Triassic Saurischia, associated with the evolution of bipedalism in various dinosaur lineages, was reversed in Late Triassic sauropodomorphs. A craniad CoM shift coincided with the evolution of quadrupedalism in the Late Triassic, followed by a more striking craniad shift in Late Jurassic-Cretaceous titanosauriforms, which included the largest sauropods. These craniad CoM shifts are strongly correlated with neck enlargement, a key innovation in sauropod evolution and pivotal to their gigantism. By creating a much larger feeding envelope, neck elongation is thought to have increased feeding efficiency and opened up trophic niches that were inaccessible to other herbivores. However, we find that relative neck size and CoM position are not strongly correlated with inferred feeding habits. Instead the craniad CoM positions of titanosauriforms appear closely linked with locomotion and environmental distributions, potentially contributing to the continued success of this group until the end-Cretaceous, with all other sauropods having gone extinct by the early Late Cretaceous.
authors.affiliation: Department of Musculoskeletal Biology, Institute of Aging and Chronic Disease , University of Liverpool , The Apex Building, 6 West Derby Street, Liverpool L7 8TX , UK.
authors.forename: Karl T
authors.initials: KT
authors.lastname: Bates
authors.affiliation: Department of Earth Science and Engineering , Imperial College London , South Kensington Campus, London SW7 2AZ , UK.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Mannion
authors.affiliation: School of Natural Sciences and Psychology , Liverpool John Moores University , James Parsons Building, Bryon Street, Liverpool L3 3AF , UK.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Falkingham
authors.affiliation: School of GeoSciences , University of Edinburgh, Grant Institute , The King's Buildings, James Hutton Road, Edinburgh EH9 3FE , UK.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Brusatte
authors.affiliation: Department of Comparative Biomedical Sciences, Structure and Motion Laboratory , Royal Veterinary College, University of London , Hatfield, Hertfordshire AL9 7TA , UK.
authors.forename: John R
authors.initials: JR
authors.lastname: Hutchinson
authors.affiliation: CONICET - División Paleontología de Vertebrados , Museo de La Plata , Paseo del Bosque s/n, La Plata B1900FWA , Argentina.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Otero
authors.affiliation: Faculty of Life Sciences , University of Manchester , Michael Smith Building, Oxford Road, Manchester M13 9PT , UK.
authors.forename: William I
authors.initials: WI
authors.lastname: Sellers
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins , Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences , 142 Xizhimenwai Dajie, Beijing 100044 , People's Republic of China.
authors.forename: Corwin
authors.initials: C
authors.lastname: Sullivan
authors.affiliation: Department of Computer and Information Science , University of Oregon , Eugene, OR 97403 , USA.
authors.forename: Kent A
authors.initials: KA
authors.lastname: Stevens
authors.affiliation: Department of Comparative Biomedical Sciences, Structure and Motion Laboratory , Royal Veterinary College, University of London , Hatfield, Hertfordshire AL9 7TA , UK.
authors.forename: Vivian
authors.initials: V
authors.lastname: Allen
keywords: biomechanics; body shape; centre-of-mass; computer modelling; gigantism; phylogeny