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New specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia.

Fanti F, Currie PJ, Badamgarav D - PLoS ONE (2012)

Bottom Line: Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs.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.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Scienze della Terra e Geologico-Ambientali, Alma Mater Studiorum, Università di Bologna, Via Zamboni, Bologna, Italy. federico.fanti@unibo.it

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.

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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.
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pone-0031330-g006: 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.

Mentions: Postcranially, the ends of most bones were destroyed, presumably by insect scavengers (Figures 3, 4). Most of the scapula (180 mm) is present, and the total length appears to have been about 185 mm. The minimum shaft width is 15 mm, and the distal end expands to 27 mm. Although the full length of the humerus is not preserved, the minimum shaft width (transverse) has a diameter of 19 mm. Amongst sixteen oviraptorosaurs (Table S4), there is a strong correlation (r2 = 0.95) between humerus length and transverse shaft width, which suggests that the humerus would have been 152 mm long in MPC-D 107/15. The ratio of the lengths of the scapula to the humerus can therefore be calculated as 1.2, which is typical of the majority of oviraptorids. The distal end of the deltoid process is preserved, but little can be said other than it was well developed and extended far down the shaft as in other oviraptorids. Only small sections of the shafts of the radius (the diameter of the shaft width is 12 mm) and ulna (SW = 14 mm) are preserved, but show that the diameter of the shaft of the radius was 0.86 that of the ulna. The length of the radius was estimated as 144 mm using 10 pairs of measurements of oviraptorid radii, plus the measurements of radii from seven individuals of the oviraptorosaurs Avimimus and Caudipteryx (b = 1.35, k = 0.75, r2 = 0.89). The estimates based on shaft widths suggest that the ratio of radius length to humerus length is 0.95, which is close to the same ratios in Citipati osmolskae (MPC-D 100/979), and Conchoraptor gracilis (MPC-D 110/21). In contrast, the ratio is less than 0.80 in Ingenia (MPC-D 100/32, 100/33, 110/03) and Rinchenia (MPC-D 100/32-1). The ratio is intermediate between the two extremes in all other oviraptorid taxa. The hands were also badly damaged, but it is clear that the phalanges (I-1, I-2) of the first digit were more massive than those of the second digit (II-2, II-3) (Fig. 6A), that the distal end of the second digit does not extend far beyond the distal end of the first digit, and that the third metatarsal is slender. These are all characters that are diagnostic for Ingeniinae.


New specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia.

Fanti F, Currie PJ, Badamgarav D - PLoS ONE (2012)

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.
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Related In: Results  -  Collection

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pone-0031330-g006: 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.
Mentions: Postcranially, the ends of most bones were destroyed, presumably by insect scavengers (Figures 3, 4). Most of the scapula (180 mm) is present, and the total length appears to have been about 185 mm. The minimum shaft width is 15 mm, and the distal end expands to 27 mm. Although the full length of the humerus is not preserved, the minimum shaft width (transverse) has a diameter of 19 mm. Amongst sixteen oviraptorosaurs (Table S4), there is a strong correlation (r2 = 0.95) between humerus length and transverse shaft width, which suggests that the humerus would have been 152 mm long in MPC-D 107/15. The ratio of the lengths of the scapula to the humerus can therefore be calculated as 1.2, which is typical of the majority of oviraptorids. The distal end of the deltoid process is preserved, but little can be said other than it was well developed and extended far down the shaft as in other oviraptorids. Only small sections of the shafts of the radius (the diameter of the shaft width is 12 mm) and ulna (SW = 14 mm) are preserved, but show that the diameter of the shaft of the radius was 0.86 that of the ulna. The length of the radius was estimated as 144 mm using 10 pairs of measurements of oviraptorid radii, plus the measurements of radii from seven individuals of the oviraptorosaurs Avimimus and Caudipteryx (b = 1.35, k = 0.75, r2 = 0.89). The estimates based on shaft widths suggest that the ratio of radius length to humerus length is 0.95, which is close to the same ratios in Citipati osmolskae (MPC-D 100/979), and Conchoraptor gracilis (MPC-D 110/21). In contrast, the ratio is less than 0.80 in Ingenia (MPC-D 100/32, 100/33, 110/03) and Rinchenia (MPC-D 100/32-1). The ratio is intermediate between the two extremes in all other oviraptorid taxa. The hands were also badly damaged, but it is clear that the phalanges (I-1, I-2) of the first digit were more massive than those of the second digit (II-2, II-3) (Fig. 6A), that the distal end of the second digit does not extend far beyond the distal end of the first digit, and that the third metatarsal is slender. These are all characters that are diagnostic for Ingeniinae.

Bottom Line: Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs.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.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Scienze della Terra e Geologico-Ambientali, Alma Mater Studiorum, Università di Bologna, Via Zamboni, Bologna, Italy. federico.fanti@unibo.it

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.

Show MeSH
Related in: MedlinePlus