title: Histology shows that elongated neck ribs in sauropod dinosaurs are ossified tendons.
abstract: The histology of cervical ribs of Sauropoda reveals a primary bone tissue, which largely consists of longitudinally oriented mineralized collagen fibres, essentially the same tissue as found in ossified tendons. The absence of regular periosteal bone and the dominance of longitudinal fibres contradict the ventral bracing hypothesis (VBH) postulated for sauropod necks. The VBH predicts histologically primary periosteal bone with fibres oriented perpendicular to the rib long axis, indicative of connective tissue between overlapping hyperelongated cervical ribs. The transformation of the cervical ribs into ossified tendons makes the neck more flexible and implies that tension forces acted mainly along the length of the neck. This is contrary to the VBH, which requires compressive forces along the neck. Tension forces would allow important neck muscles to shift back to the trunk region, making the neck much lighter.
authors.affiliation: Steinmann Institute, Division of Palaeontology, University of Bonn, Bonn 53115, Germany. nklein@uni-bonn.de
authors.forename: Nicole
authors.initials: N
authors.lastname: Klein
authors.forename: Andreas
authors.initials: A
authors.lastname: Christian
authors.forename: P Martin
authors.initials: PM
authors.lastname: Sander
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D057070:Cervical Rib / Q000033:anatomy & histology* / Q000737:chemistry; D003094:Collagen / Q000032:analysis; D025061:Dinosaurs / Q000033:anatomy & histology*; D005580:Fossils; D006652:Histological Techniques; D008954:Models, Biological; D010012:Osteogenesis / Q000502:physiology; D013710:Tendons / Q000033:anatomy & histology* / Q000737:chemistry
chemical_list: D003094:Collagen