their brood for more than 40 days with limited food and water supplies. In desert environments, thermal stress may be most critical during reproduction, as the adult is restricted to the nest for large portions of the day. Furthermore, eggs and nestlings are particularly susceptible to thermal damage. Mechanisms allowing successful incubation in extreme heat, such as a specific choice of the nesting area, must have existed in the Late Cretaceous Gobi. One suggestion for the appearance and evolution of rectrices in oviraptorosaurs is as an adaptation to shade and protect eggs in the nest [74,75]. The new specimens demonstrate that Nemegtomaia is similar to derived ingeniine oviraptorids like Heyuannia, Ingenia and Machair- asaurus in having a robust, relatively short manus with a robust metacarpal I that had a powerful ungual. There are relatively few oviraptorid specimens (eight) that have both femora and hands preserved. Nevertheless, regression analysis of a suite of theropods shows that the lengths of the second metacarpals in Citipati and Khaan are close to what would be expected in a velociraptorine dromaeosaurid, whereas the lengths of the metacarpi are reduced in Ingenia and Nemegtomaia. The relative lengths of different elements of the hand of ingeniines should be thought of in terms of the relative shortening of the second digit rather than the lengthening of the third metacarpal. During theropod evolution, the first metacarpal becomes relatively shorter in relation to the length of the second metacarpal. An ingeniine seems to have a relatively long first metacarpal compared with the second metacarpal, but this is not a reversal in the theropod trend because it is accomplished in a different manner (through the shortening of the second metacarpal rather than by increasing the length of the first metacarpal). Nevertheless, there are changes in the ingeniine metacarpal I in that it becomes relatively thicker to support a more robust finger, and it expands to cover the posteroventral surface of the second metacarpal at the proximal end. This presumably immobilizes the metacarpus, and in the holotype of Ingenia (MPC-D 100/30), this is taken a step further through coossification of the semilunate carpal with the three metacarpals. The phalanges in digit II also become relatively shorter in comparison with the second metacarpal so that the finger overall is also shortened. This presumably is associated with a change in function, and may have something to do with the presence of long remiges behind the forelimb that also attach to the second manual digit. A similar trend of digital reduction (especially in the ungual) can be found in Confuciusornis [76]. As the second digit assumed the function of feather support, it reduced its capability for using it as a grasping appendage. This function seems to have been largely taken over by the first digit, which is probably why it became more robust in the Ingeniinae. The size reduction of the third finger is a logical consequence of the feathered hand because it would be positioned above and behind the feathers where it could not be used effectively for grasping. Nemegtomaia barsboldi is the only member of the subfamily Ingeniinae that is known to have a crest. Crestless skulls of other ingeniines (Conchoraptor, Heyuannia and Khaan) are smaller than either of the two skulls of Nemegtomaia, which makes it possible that crest development is controlled by ontogeny or by absolute size. The crests tend to be highly pneumatic, and the presence of pneumatic nasals and frontals in at least Conchoraptor suggests that they had the potential for inflating these bones into crests in larger, more mature individuals. This taxon is known from the Baruungoyot Formation, from which at least two specimens of Nemegtomaia have been recovered. However, many skulls and skeletons of Conchoraptor have been collected in recent years and they are all of the same uniform small size. Their numbers, and the fact that at least one of the Ingenia specimens (MPC-D 100/30) has New Specimens of Nemegtomaia from Mongolia a coossified carpometacarpus, suggest that these animals probably never became as large as Nemegtomaia. Ingeniinae are characterized by having seven or eight vertebrae incorporated into the synsacrum, whereas other oviraptorids have only six vertebrae incorporated into the sacrum. Irrespective of size, ingeniines have longer deltopectoral crests, more bowed ulnar shafts, and shorter hands with more powerful first manual digits. Conclusions Nemegtomaia is the fourth genus of an oviraptorid dinosaur that has been found on top of a nest, but is the first within the Ingeniinae clade. Although the name means ‘‘good mother of Nemegt’’, it received that name before there was any association between adults and eggs. Although the phylogenetic analysis of Lu et al. [19] found that Nemegtomaia was most closely related to the oviraptorine Citipati, the recovery of additional specimens clearly shows it to be an ingeniine oviraptorid. The hands of Ingeniinae genera are shorter than those of oviraptorines, but have more robust first digits. The more powerful claw on the first manual digit, the reduction in the length of the second manual digit, and reduction in size of the third finger are probably characters correlated with the presence of rectrices on the forelimb of these oviraptorids that were possibly used to protect the eggs in nests. Oviraptorid dinosaurs were one of the most common types of animals in arid environments during Late Cretaceous times of central Asia; nesting areas may have been selected with respect to nearby channel systems. Supporting Information Table S1 Characters modified from, or added to, the character list of Longrich et al. [11]. Additional data on for caenagnathids as in [77] and for Heyuannia as in [78]. (DOC) Table S2 Character description. Characters for phyloge- netic analysis of the relationships among oviraptorosauria (modified after Longrich et al. [11]). (DOC) Table S3 (DOC) Character-taxon matrix. Table S4 Selected measurements of oviraptorids. Se- lected measurements of oviraptorids used for calculating the lengths of missing elements in MPC-D 107/15 and MPC-D 107/ 16. Measures in millimeters (PJC). Abbreviations: SL, skull length (preferably from the edge of paraoccipital process to the tip of the premaxilla, but in most cases taken from the quadrate to the premaxilla); Pm1, premaxilla height (below naris); Pm2, premaxilla height; Ao sl, antorbital skull length; o l, orbital length; d, dentary length; d 2, dentary maximum height; j l, jaw length; sc l, scapula blade length; sc sw, scapula shaft width; h l, humerus length; h sw, humerus shaft width; r l, radius length; r sw, radius shaft width; u l, ulna length; u sw, ulna shaft width; mc I, metacarpal 1; mc II, metacarpal 2; mc III, metacarpal 3; I-1, first digit, first phalanx; I-2, first digit, second phalanx; II-1, second digit, first phalanx; II-2, second digit, second phalanx; II- 3, second digit, third phalanx; III-1, third digit, first phalanx; il l, ilium length; f l, femur length; f sw, femur shaft width; f c, femur shaft circumference; t l, tibia length; t sw, tibia shaft width; III-3, digit three, third phalanx; IV-2, digit four, second phalanx; IV-3, digit four, third phalanx; IV-4, digit four, fourth phalanx; IV-5, digit four, fifth phalanx. Additional data on oviraptorid specimens: Gigantoraptor erlianensis [79]; Hagryphus giganteus [80]; Heyuannia huangi [81]; Oviraptor philoceratops [1]; Oviraptor incertae sedis [82]. (XLS) PLoS ONE | www.plosone.org 14 February 2012 | Volume 7 | Issue 2 | e31330