Background The Late Cretaceous Nemegt Formation, Gobi Desert, Mongolia has already yielded abundant and complete skeletons of the hadrosaur Saurolophus angustirostris, from half-grown to adult individuals. Methodology/Principal Findings Herein we describe perinatal specimens of Saurolophus angustirostris, associated with fragmentary eggshell fragments. The skull length of these babies is around 5% that of the largest known S. angustirostris specimens, so these specimens document the earliest development stages of this giant hadrosaur and bridge a large hiatus in our knowledge of the ontogeny of S. angustirostris. Conclusions/Significance The studied specimens are likely part of a nest originally located on a riverbank point bar. The perinatal specimens were buried by sediment carried by the river current presumably during the wet summer season. Perinatal bones already displayed diagnostic characters for Saurolophus angustirostris, including premaxillae with a strongly reflected oral margin and upturned premaxillary body in lateral aspect. The absence of a supracranial crest and unfused halves of the cervical neural arches characterize the earliest stages in the ontogeny of S. angustirostris. The eggshell fragments associated with the perinatal individuals can be referred to the Spheroolithus oogenus and closely resemble those found in older formations (e.g. Barun Goyot Fm in Mongolia) or associated with more basal hadrosauroids (Bactrosaurus-Gilmoreosaurus in the Iren Dabasu Fm, Inner Mongolia, China). This observation suggests that the egg microstructure was similar in basal hadrosauroids and more advanced saurolophines. Competing Interests One of the authors (FE) is employed by the commercial organization Eldonia. Eldonia provided support in the form of a salary for FE, but did not have any additional role or influence in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and it does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials.
Directorate 'Earth and History of Life', Royal Belgian Institute of Natural Sciences, rue Vautier 29, B-1000, Brussels, Belgium;Research Unit Palaeontology, Department Geology and Soil Sciences, Ghent University, Krijgslaan 281, 9000, Ghent, Belgium;Institute of Paleontology and Geology, Mongolian Academy of Sciences, Ulaanbaatar, 210–351, Mongolia;Institute of Paleontology and Geology, Mongolian Academy of Sciences, Ulaanbaatar, 210–351, Mongolia;Université de Poitiers, IPHEP, UMR CNRS 7262, 6 rue M. Brunet, 86073, Poitiers cedex 9, France;Earth System Science, AMGC, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium;Eldonia, 9 Avenue des Portes Occitanes, 3800, Gannat, France;Directorate 'Earth and History of Life', Royal Belgian Institute of Natural Sciences, rue Vautier 29, B-1000, Brussels, Belgium
Recommended Citation:
Leonard Dewaele,Khishigjav Tsogtbaatar,Rinchen Barsbold,et al. Perinatal Specimens of Saurolophus angustirostris (Dinosauria: Hadrosauridae), from the Upper Cretaceous of Mongolia[J]. PLOS ONE,2015-01-01,10(10)