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Science 29 July 2005:
Vol. 309. no. 5735, pp. 761 - 764
DOI: 10.1126/science.1114942
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Reports

Embryos of an Early Jurassic Prosauropod Dinosaur and Their Evolutionary Significance

Robert R. Reisz,1* Diane Scott,1 Hans-Dieter Sues,2 David C. Evans,1 Michael A. Raath3

Articulated embryos from the Lower Jurassic Elliot Formation of South Africa are referable to the prosauropod Massospondylus carinatus and, together with other material, provide substantial insights into the ontogenetic development in this early dinosaur. The large forelimbs and head and the horizontally held neck indicate that the hatchlings were obligate quadrupeds. In contrast, adult Massospondylus were at least facultatively bipedal. This suggests that the quadrupedal gait of giant sauropods may have evolved by retardation of postnatal negative allometry of the forelimbs. Embryonic body proportions and an absence of well-developed teeth suggest that hatchlings of this dinosaur may have required parental care.

1 Department of Biology, University of Toronto at Mississauga, Mississauga, ON L5L 1C6, Canada.
2 Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA.
3 Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, Wits 2050, Johannesburg, South Africa.

* To whom correspondence should be addressed. E-mail: rreisz{at}utm.utoronto.ca

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Ontogenetic stages in the long bone histology of sauropod dinosaurs.
N. Klein and M. Sander (2008)
Paleobiology 34, 247-263
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Developmental Plasticity in the Life History of a Prosauropod Dinosaur.
P. M. Sander and N. Klein (2005)
Science 310, 1800-1802
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Science. ISSN 0036-8075 (print), 1095-9203 (online)