title: Long bone histology and growth patterns in ankylosaurs: implications for life history and evolution.
abstract: The ankylosaurs are one of the major dinosaur groups and are characterized by unique body armor. Previous studies on other dinosaur taxa have revealed growth patterns, life history and evolutionary mechanisms based on their long bone histology. However, to date nothing is known about long bone histology in the Ankylosauria. This study is the first description of ankylosaurian long bone histology based on several limb elements, which were sampled from different individuals from the Ankylosauridae and Nodosauridae. The histology is compared to that of other dinosaur groups, including other Thyreophora and Sauropodomorpha. Ankylosaur long bone histology is characterized by a fibrolamellar bone architecture. The bone matrix type in ankylosaurs is closest to that of Stegosaurus. A distinctive mixture of woven and parallel-fibered bone together with overall poor vascularization indicates slow growth rates compared to other dinosaurian taxa. Another peculiar characteristic of ankylosaur bone histology is the extensive remodeling in derived North American taxa. In contrast to other taxa, ankylosaurs substitute large amounts of their primary tissue early in ontogeny. This anomaly may be linked to the late ossification of the ankylosaurian body armor. Metabolically driven remodeling processes must have liberated calcium to ossify the protective osteodermal structures in juveniles to subadult stages, which led to further remodeling due to increased mechanical loading. Abundant structural fibers observed in the primary bone and even in remodeled bone may have improved the mechanical properties of the Haversian bone.
authors.affiliation: Steinmann Institut für Geologie, Mineralogie und Paläontologie, Universität Bonn, Bonn, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Stein
authors.forename: Shoji
authors.initials: S
authors.lastname: Hayashi
authors.forename: P Martin
authors.initials: PM
authors.lastname: Sander
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001842:Bone and Bones / Q000033:anatomy & histology / Q000502:physiology*; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification / Q000502:physiology*; D010802:Phylogeny
references.citation: Anat Embryol (Berl). 1993 Mar;187(3):239-48
references.pmid: 8470824
references.citation: PLoS One. 2009 Oct 27;4(10):e7626
references.pmid: 19859556
references.citation: Bone. 2007 Apr;40(4):1152-8
references.pmid: 17223615
references.citation: PLoS One. 2009 Aug 25;4(8):e6738
references.pmid: 19707581
references.citation: Science. 1976 Jun 11;192(4244):1123-5
references.pmid: 17748675
references.citation: Proc Natl Acad Sci U S A. 2010 May 18;107(20):9258-63
references.pmid: 20435913
references.citation: PLoS One. 2012;7(5):e36904
references.pmid: 22666333
references.citation: Bone. 1993 Mar-Apr;14(2):103-9
references.pmid: 8334026
references.citation: Science. 2005 Jun 3;308(5727):1456-60
references.pmid: 15933198
references.citation: Am J Anat. 1962 May;110:269-305
references.pmid: 13890323
references.citation: Nature. 2001 Jul 26;412(6845):429-33
references.pmid: 11473315
references.citation: Med Hypotheses. 1999 Nov;53(5):363-8
references.pmid: 10616033
references.citation: Anat Embryol (Berl). 1993 Mar;187(3):231-8
references.pmid: 8470823
references.citation: Nature. 2001 Jul 26;412(6845):405-8
references.pmid: 11473307
references.citation: Calcif Tissue Int. 1993;53 Suppl 1:S47-55; discussion S56
references.pmid: 8275380
references.citation: Nature. 2004 Aug 12;430(7001):772-5
references.pmid: 15306807
references.citation: Nature. 2006 Jun 8;441(7094):739-41
references.pmid: 16760975
references.citation: Arch Oral Biol. 1996 Oct;41(10):941-50
references.pmid: 9031701
references.citation: Proc Natl Acad Sci U S A. 2008 Jan 15;105(2):582-7
references.pmid: 18195356
references.citation: J Morphol. 2006 Mar;267(3):347-59
references.pmid: 16380967