Bone microstructure of the Upper Cretaceous titanosaur sauropod Neuquensaurus australis Lyde kker , 1893

IGNACIO A. CERDA; LEONARDO SALGADO

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

We present the bone histology of Neuquensaurus australis Lydekker, 1893, a saltasaurini titanosaur from the Upper Cretaceous of Patagonia, and explore its paleobiological implications. The sample analyzed includes diverse axial and appendicular elements of several specimens, including different bones belonging to a single one (MCS-Pv 5, Museo de Cinco Saltos, Paleovertebrados). Long bones consist of compact bone cortex enclosing a medullar core filled with secondary cancellous tissue. The cortical bone tissue is mostly composed of dense Haversian bone tissue. Primary bone remains are preserved in the outer cortex, and consist of fibro-lamellar bone tissue. Growth marks are present as annuli and/or lines of arrested growth. The externalmost cortex of some specimens reveals the deposition of an outer circumferential layer (OCL). Internally, axial bones are composed of a compact cortex of variable thickness that surrounds a camellate bone tissue. The camellate structure consists entirely of secondary bone tissue. The long bone histology of N. australis indicates that the growth of this sauropod dinosaur was cyclic in ?at least? the later phase of its ontogeny. The presence of an OCL reveals a determinate growth. Dense Haversian bone tissue in the cortex of the limb bones has been recorded previously in other sauropods such as Alamosaurus sanjuanensis Gilmore, 1922 and Lirainosaurus astibiae Sanz, Powell, Le Loeuff, Martínez and Pereda Suberbiola,, 1999 (Woodward and Lehman, 2009; Company, 2011) and appears to be a common feature of advanced titanosaurs.