Nomadic Expedition’s ‘‘Dinosaurs of the Gobi’’ 2007 party recovered two new specimens of oviraptorids from the Baruun- goyot Formation (or ‘‘Barun Goyot’’ in older literature; strati- graphic terminology in this paper follows [24]) beds at the Nemegt locality (Figure 1). Specimen MPC-D 107/15 is a nest of eggs with the presumed mother lying on top. In addition to being found less than 500 m from the holotype of Nemegtomaia, the new specimen shares diagnostic characters of the skull and has the same absolute body size. It provides new anatomical information about the front limbs that conclusively shows that Nemegtomaia should be referred to the subfamily Ingeniinae. The second new specimen, MPC-D 107/16, consists of hands, ribs, a partial pelvis and both femora of a smaller individual. The two new specimens are described here with a focus on diagnostic and previously unknown characters (especially in the skull and hands), the association of the skeleton with the eggs, and the taphonomy, stratigraphic range, and paleoecology of the taxon. Institutional Abbreviations AMNH, American Museum of Natural History, New York, USA; IVPP, Institute of Vertebrate Paleontology and Paleoan- thropology, Beijing, People’s Republic of China: MPC-D, Paleontological Center of the Mongolian Academy of Sciences, Ulaan Baatar, Mongolia ( = GIN, Geological Institute, Mongolian Academy of Sciences); UALVP, University of Alberta, Laboratory of Vertebrate Paleontology, Edmonton, Canada. Geology and Stratigraphy Since its discovery in 1946, the Nemegt locality (sensu [15]) has been recurrently investigated for the rich and diverse fossil fauna preserved in the exposed Upper Cretaceous sediments (Figure 1). Several major sayrs (canyons, gorges) and numerous side-canyons cut the pediment that slopes toward the south beneath the Nemegt massif. The cuts are up to 45 meters deep and provide some of the New Specimens of Nemegtomaia from Mongolia best exposures of the upper Campanian - lower Maastrichtian Baruungoyot and Nemegt formations, which have been largely discussed in the literature [25–33]. Specimen MPC-D 107/15 was collected from the upper Baruungoyot Formation deposits that crop out extensively along the Northern Sayr. These upper beds are barren of mudstone and consist of a stacked succession of tabular redbeds. Abundant extraformational clasts, well-developed caliches, and invertebrate feeding traces characterize these primarily aeolian deposits (Figure 2). Wedging out of single beds is fairly common, even though individual tabular beds can be traced laterally for tens or hundreds of meters. Prospecting activities carried out in Northern Sayr revealed the lateral variation of such beds, even within the cliff in which the nest was discovered (Fig. 2B). A short distance (150 meters) to the north of the nest, the distinctive Baruungoyot facies interfinger with light grey, trough cross-bedded channel deposits that are typical of the Nemegt Formation. The basal contact is sharp and erosive, juxtaposing fine- to medium-grained sandstone with a medium- grained, 5 cm thick conglomerate that fines upward into cross- bedded sandstones. Such beds form an approximately four meter thick, fining-upward tongue that is conformably overlaid by red, massive, aeolian deposits (Baruungoyot facies). Finally, the channel fill sandstone deposits of the Nemegt Formation cap this interval (Fig. 2F). The two formations and their different fossil assemblages have historically been considered to represent sequential periods of time and different environments [26,27,34–36]: the Baruungoyot Formation is indicative of semi-arid or arid environments with recurrent aeolian beds, and the Nemegt Formation has been interpreted as representing a dominantly fluvial environment with most fossils being recovered from channel fills, point bars, and some overbank deposits laid down under more humid conditions [33]. However, new data collected in the Northern Sayr at the Nemegt locality document an approximately 25 meter thick stratigraphic interval where the two formations interfinger, and Figure 1. The Nemegt locality the Gobi Desert, southern Mongolia. A, map showing the location of the study area within southern Mongolia; B, the Nemegt area is located a few kilometers south of the massif of the same name; C, a detail of the Nemegt locality (sensu 5), showing the exact locations of specimens described in this study. doi:10.1371/journal.pone.0031330.g001 PLoS ONE | www.plosone.org 2 February 2012 | Volume 7 | Issue 2 | e31330