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, 7 (2), e31330

New Specimens of Nemegtomaia From the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia


New Specimens of Nemegtomaia From the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia

Federico Fanti et al. PLoS One.


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.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Figure 1
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.
Figure 2
Figure 2. Location map showing the position of the measured section discussed in the text.
A, Northern Sayr, where specimen MPC-D 107/15 was collected. B, lithostratigraphic logs showing the relative stratigraphic occurrence of the interfingering Baruungoyot and Nemegt formations. C, In-situ and partially reworked caliche glaebules and concretions, Baruungoyot Formation. D, tubular burrow fills interpreted as nonmarine invertebrate feeding traces, Baruungoyot Formation. E, cross-bedded deposits in the basal deposits of the Nemegt Formation. F, photograph showing the interfingering contact between the Baruungoyot and Nemegt formations in the Northern Sayr (litho-log c). MPC-D 107/15 was collected just below the Nemegt tongue deposits.
Figure 3
Figure 3. Nest and preserved elements of Nemegtomaia barsboldi (MPC-D 107/15).
A, dorsal view; B, left lateral view; C, right lateral view; D, posterior view. lf, left femur; lfi, left fibula; lh, left humerus; lm, left manus; lp, left pes; lpu, left pubis; lr, left radius; ls, left scapula; lt, left tibia; lu, left ulna; rf, right femur; rfi, right fibula; rh, right humerus; rp, right pes; rpu, right pubis; rs, right scapula; rt, right tibia; sk, skull. Scale bar 10 cm. Reconstruction by Marco Auditore.
Figure 4
Figure 4. Feeding traces left by colonies of dermestid beetles in specimen MPC-D 107/15.
Articular surfaces have been completely obliterated in the left forearm (A), left leg and pes (B), as well as in the right forearm (C). Circular borings are particularly evident in the left side of the skull (D–F). G, Bone-chip burrow found under the skull of the specimen. H, large traces of reworked sediment under the skeleton.
Figure 5
Figure 5. Skull of Nemegtomaia barsboldi (MPC-D 107/15).
A, preserved elements of the right side; B, preserved elements of the left side; C, reversed elements of the left side superimposed to those of the right side (where elements of both sided overlap, the grey is darker); D, reconstruction of the skull. an, angular; d, dentary; ec, ectopterygoid; eo, exoccipital; f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; p, parietal; pm, premaxilla; po, postorbital; q, quadrate; qj, quadratojugal; sa, surangular; sq, squamosal; sr, sclerotic ring. Scale bar 10 cm. Illustration by Marco Auditore.
Figure 6
Figure 6. Hands of Nemegtomaia barsboldi.
A, preserved elements and reconstructed manus of MPC-D 107/15 in dorsal (a1) and lateral (a2) views: B, right manus of MPC-D 107/16 in dorsal (b1) and medial (b2) views; C, left manus of MPC-D 107/16 in medial (c1) and dorsal (c2) views, with the preserved distal portions of radius and ulna. lr, left radius; lu, left ulna. Scale bar 5 cm. Illustration by Marco Auditore.
Figure 7
Figure 7. Skeletons of Nemegtomaia barsboldi specimens (known elements in grey).
A, the holotype (MPC-D 100/2112); B, MPC-D 107/15 (the left side of the skull, left forelimb, pubis and toes are reversed and superimposed to the right side). C, MPC-D 107/16 (the left forelimb is reversed and superimposed to the right side). In D, the preserved elements of MPC-D 107/15 and 16 are scaled to and superimposed on the holotype (the skull depicted is that of the better preserved MPC-D 100/2112). Scale bar 20 cm. Illustration by Marco Auditore.
Figure 8
Figure 8. Phylogeny of Oviraptoridae.
Phylogenetic analysis of Oviraptoridae was performed by adapting the matrix of Longrich et al. (3) and using the exhaustive search algorithm of PAUP* 4.0b10. Numbers next to clades indicate bootstrap support value/decay value.
Figure 9
Figure 9. The nest of Nemegtomaia barsboldi, MPC-D 107/15.
A, disposition of preserved eggs within the nest. Eggshells have been recovered under the skull (B), left pes (C) and leg (D), suggesting the direct apposition of the oviraptorid on top of the eggs. During the early excavation of the nest, it was possible to document a lower layer of eggs lying approximately 10 cm below the body (E–G).
Figure 10
Figure 10. Eggs of Nemegtomaia barsboldi.
Details of eggs preserved in the upper layer of eggs in specimen MPC-D 107/15. Scale bar A–E 5 cm.

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