Company, Julio

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HANTKENIANA 5 (2006)   82   Bone histology of the ornithopod dinosaur Rhabdodon from the Late Cretaceous of the Iberian Peninsula — Preliminary data  Julio COMPANY  Departamento de Ingeniería del Terreno, U.P.V., 46022 Valencia, Spain, e-mail: company@uv.es   Rhabdodon is an ornithopod dinosaur common in Late Cretaceous continental deposits from central and western and central Europe (Norman, 2004). Even though Rhabdodon histological sections had been documented since the beginning of the 20th century (Nopcsa, 1933: rib sections) to recent decades (Reid, 1985, 1990: limb bones, ribs), not any detailed de-scription of its histological characterization has been made to date. The Late Cretaceous Chera locality (Valencia pro-vince, Spain) has yielded a large amount of Rhabdodon remains, which has permitted the realisation of a considerable number of polished and transverse thin-sections, mainly from long bones (ribs, humeri, tibiae, femora) and axial elements (caudal vertebrae) of both juvenile and adult individuals. Rhabdodon long bone structure consists of a thick cortex composed mainly of primary compact bone enclosing a well developed medullary cavity, devoid of bony trabeculae. The cortical region is formed by deposition of primary bone tissue of fibro-lamellar type (Francillon-Vieillot, 1990). Haversian (i. e., se-condary) reconstruction is evidenced by the occasional presence of scattered secondary osteons, visible throughout the cortex. Middle to outer regions of the cortex exhibit a stratification into layers, due to the presence of lines of arrested growth (LAGs) which mark pauses of bone deposition. In general, the vascularity of the cortex grades from an innermost highly vascularized region with predominately reti-cular to locally subplexiform vascularization to an external region with longitudinal to laminar vascular-ized bone tissue. Finally, the outermost periosteal cortex consists of nearly avascular bone. Thus, histological examinations of diaphyseal transverse sections reveal most of Rhabdodon indi-vidual’s life history, suggesting a initial phase of fast and continuous growth early in ontogeny (de-position of high vascularized fibro-lamellar bonetissue), followed by a gradual decline in the rate of growth (evidenced by a more organized longitudinal vascularity and presence of interruptions in bone deposition), and a final growth cessation (deposition of external layers of an almost avascular tissue). Interpretation of rest lines (LAGs) as annual events permits an estimation of the age at which the animal reaches adult size from the number of rings present in adult samples (Chinsamy, 2005, and references therein). Thus, it has been estimated a minimum age of about eight to ten years for Rhabdodon to reach its final body size.  References Chinsamy, A. 2005. The Microstructure of Dinosaur Bone: Deciphering Biology with Fine-Scale Techniques. Johns Hopkins University Press, Baltimore, 216 pp. Francillon-Vieillot, H., De Buffrénil, V., Castanet, J., Géraudie, J. & Meunier, F.J. 1990. Microstructure and mineralization of vertebrate skeletal tissues. In: Carter, J.G. (ed.), Skeletal biomineralization: patterns, processes and evolutionary trends. V. I. Van Nostrand Reinhold, New York, 471-530. Nopcsa, F. 1933. On the Histology of the ribs in immature and half-grown Trachodont dinosaurs. Proceedings of the zoological society of London, 221-223. Norman, D.B. 2004. Basal Iguanodontia. In: Weishampel, D.B., Dodson, P. & Osmólska, H. (eds.), The Dinosauria. Second Edition. University of California Press, Berkeley, 413-437. Reid, R.E.H. 1985. On Supposed Haversian Bone from the Hadrosaur Anatosaurus and the Nature of Compact Bone in Dinosaurs. Journal of Paleontology, 59: 140-148. Reid, R.E. 1990. Zonal „growth rings” in dinosaurs. Modern Geology, 15: 19-48. 

Bone histology of the ornithopod dinosaur Rhabdodon from the Late Cretaceous of the Iberian Peninsula — Preliminary data

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Bone histology of the ornithopod dinosaur Rhabdodon from the Late Cretaceous of the Iberian Peninsula — Preliminary data

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