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Science 3 June 2005:
Vol. 308. no. 5727, pp. 1456 - 1460
DOI: 10.1126/science.1112158
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Reports

Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex

Mary H. Schweitzer,1,2,3* Jennifer L. Wittmeyer,1 John R. Horner3

Unambiguous indicators of gender in dinosaurs are usually lost during fossilization, along with other aspects of soft tissue anatomy. We report the presence of endosteally derived bone tissues lining the interior marrow cavities of portions of Tyrannosaurus rex (Museum of the Rockies specimen number 1125) hindlimb elements, and we hypothesize that these tissues are homologous to specialized avian tissues known as medullary bone. Because medullary bone is unique to female birds, its discovery in extinct dinosaurs solidifies the link between dinosaurs and birds, suggests similar reproductive strategies, and provides an objective means of gender differentiation in dinosaurs.

1 Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA.
2 North Carolina State Museum of Natural Sciences, Raleigh, NC 27601, USA.
3 Museum of the Rockies, Montana State University, Bozeman, MT 59717, USA.

* To whom correspondence should be addressed. E-mail: schweitzer{at}ncsu.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
From the Cover: Sexual maturity in growing dinosaurs does not fit reptilian growth models.
A. H. Lee and S. Werning (2008)
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Analyses of Soft Tissue from Tyrannosaurus rex Suggest the Presence of Protein.
M. H. Schweitzer, Z. Suo, R. Avci, J. M. Asara, M. A. Allen, F. T. Arce, and J. R. Horner (2007)
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Protein Sequences from Mastodon and Tyrannosaurus Rex Revealed by Mass Spectrometry.
J. M. Asara, M. H. Schweitzer, L. M. Freimark, M. Phillips, and L. C. Cantley (2007)
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M. E. McNamara, P. J. Orr, S. L. Kearns, L. Alcala, P. Anadon, and E. Penalver-Molla (2006)
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Science. ISSN 0036-8075 (print), 1095-9203 (online)