New Specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia Federico Fanti1*, Philip J. Currie2, Demchig Badamgarav3 1 Dipartimento di Scienze della Terra e Geologico-Ambientali, Alma Mater Studiorum, Universita` di Bologna, Via Zamboni, Bologna, Italy, 2 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, 3 Paleontological Center, Mongolian Academy of Sciences, Ulaan Baatar, Mongolia Abstract Two new specimens of the oviraptorid theropod Nemegtomaia barsboldi from the Nemegt Basin of southern Mongolia are described. Specimen MPC-D 107/15 was collected from the upper beds of the Baruungoyot Formation (Campanian- Maastrichtian), and is a nest of eggs with the skeleton of the assumed parent of Nemegtomaia on top in brooding position. Much of the skeleton was damaged by colonies of dermestid coleopterans prior to its complete burial. However, diagnostic characters are recovered from the parts preserved, including the skull, partial forelimbs (including the left hand), legs, and distal portions of both feet. Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs. The second new specimen, MPC-D 107/16, was collected a few kilometers to the east in basal deposits of the Nemegt Formation, and includes both hands and femora of a smaller Nemegtomaia individual. The two formations and their diverse fossil assemblages have been considered to represent sequential time periods and different environments, but data presented here indicate partial overlap across the Baruungoyot-Nemegt transition. All other known oviraptorids from Mongolia and China are known exclusively from xeric or semi-arid environments. However, this study documents that Nemegtomaia is found in both arid/aeolian (Baruungoyot Formation) and more humid/fluvial (Nemegt Formation) facies. Citation: Fanti F, Currie PJ, Badamgarav D (2012) New Specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia. PLoS ONE 7(2): e31330. doi:10.1371/journal.pone.0031330 Editor: Carles Lalueza-Fox, Institut de Biologia Evolutiva - Universitat Pompeu Fabra, Spain Received June 14, 2011; Accepted January 6, 2012; Published February 8, 2012 Copyright: 2012 Fanti et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported with funding by the Dinosaur Research Institute (Calgary), the Museo Geologico Giovanni Capellini (Bologna, Italy), and NSERC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: federico.fanti@unibo.it Introduction Oviraptorid dinosaurs have long been a source of information and speculation about the behavior of non-avian theropods [1,2]. Known since the Third Central Asiatic Expedition led by Roy Chapman Andrews [3] and for decades mistakenly referred to as exemplary egg thieves, this group of edentulous maniraptoran dinosaurs is now studied for its sophisticated social structure and behavior, which includes the brooding and care of eggs in specially prepared nests [4–9]. The family Oviraptoridae, known to date from the Late Cretaceous of Asia where multiple complete or nearly complete skeletons have been recovered, includes two widely accepted clades, Ingeniinae and Oviraptorinae [10,11]. Barsbold [12] established the subfamily Ingeniinae, and separated ingeniines from oviraptorines on the basis of their smaller size and reduced manual digits II and III. The clade included both Conchoraptor and Ingenia. The first detailed phylogenetic analysis of the Oviraptoridae was published by Maryan´ ska et al. [13]. They retrieved Conchoraptor and Ingenia in a monophyletic clade defined by a scapula to humerus ratio greater than 0.7, a deltopectoral crest that extends for 40%–50% of the length of humerus, a metacarpal II to metacarpal III ratio that is less than 0.5, and a postacetabular process of the ilium that has a truncated distal end. Osmo´ lska et al. [10] defined ingeniines as Conchoraptor gracilis and Ingenia yanshini, their most recent common ancestor, and all descendants. The three synapomorphies they used to define the subfamily are: the synsacrum includes seven to eight vertebrae; the deltopectoral crest extends for 40%–50% of the length of humerus; and the postacetabular process of the ilium has a truncated distal end. Khaan mckennai was included in the Ingeniinae, and is clearly similar to Conchoraptor. Nemegtomaia barsboldi [14] is unusual in that it is the only ingeniine that has a cranial crest, and is the only oviraptorid that was collected from fluvial (instead of xeric) deposits. The type specimen (MPC-D 100/2112) was collected in 1996 in southern Mongolia at the Nemegt locality (sensu [15]) by the Mongolian Highland Interna- tional Dinosaur Project [14]. It included the skull and partial skeleton (thirteen cervical, six dorsal, eight sacral and two caudal vertebrae, left scapula, distal ends of both humeri, right radius, both ilia, proximal ends of both pubes, both ischia, and proximal end of a femur). However, characters of the forelimbs and hands that are diagnostic for determining interspecific variation [11,16], were unknown. Furthermore, no eggs or eggshells were found in association with the specimen. The specimen was originally referred to as Ingenia sp. by L u¨ et al. [17] but a detailed revision of the specimen led to it being renamed Nemegtia barsboldi [14]. However, the genus had to be renamed Nemegtomaia when it was realized that the name was preoccupied by a freshwater ostracod from the Nemegt Formation [18,19]. Nemegtomaia (‘‘good mother of Nemegt’’) refers not only to the stratigraphic and geographic location of the discovery (early Maastrichtian Nemegt Formation, Nemegt locality, southern Gobi, Mongolia) but also to the idea that oviraptorid dinosaurs were brooding, rather than stealing, eggs [4,5,7–9,20–23]. PLoS ONE | www.plosone.org 1 February 2012 | Volume 7 | Issue 2 | e31330