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Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus

  1. Adam M. Yatese
  1. aDepartment of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada;
  2. bRoyal Ontario Museum, Toronto, ON M5S 2C6, Canada;
  3. cSchool of Earth and Environmental Sciences, James Cook University, Townsville, 4811 QLD, Australia;
  4. dDepartment of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013; and
  5. eBernard Price Institute for Palaeontological Research, University of the Witwatersrand, Wits 2050, Johannesburg, South Africa
  1. Edited by Steven M. Stanley, University of Hawaii, Honolulu, HI, and approved December 16, 2011 (received for review June 10, 2011)

Abstract

The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding.

Footnotes

  • ?1To whom correspondence should be addressed. E-mail: robert.reisz{at}utoronto.ca.
  • Author contributions: R.R.R. designed research; R.R.R., D.C.E., and E.M.R. performed research; R.R.R., D.C.E., E.M.R., H.-D.S., and A.M.Y. analyzed data; and R.R.R., D.C.E., E.M.R., H.-D.S., and A.M.Y. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1109385109/-/DCSupplemental.

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