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Reidentification of Avian Embryonic Remains from the Cretaceous of Mongolia

Published on Jun 1, 2015in PLOS ONE2.78
· DOI :10.1371/journal.pone.0128458
David J. Varricchio28
Estimated H-index: 28
(MSU: Montana State University),
Amy M. Balanoff15
Estimated H-index: 15
(SBU: Stony Brook University),
Mark A. Norell57
Estimated H-index: 57
(AMNH: American Museum of Natural History)
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Abstract
Embryonic remains within a small (4.75 by 2.23 cm) egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT) was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar) 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus) identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.
  • References (34)
  • Citations (13)
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References34
Newest
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#2S. Chatterjee (Museum of Texas Tech University)H-Index: 1
Last.K. E. Mikhailov (RAS: Russian Academy of Sciences)H-Index: 1
view all 3 authors...
#1Chunling Gao (AMNH: American Museum of Natural History)H-Index: 9
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#2Jaime E. Powell (CONICET: National Scientific and Technical Research Council)H-Index: 12
Last.Martin Kundrát (Uppsala University)H-Index: 11
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#1David E. Fastovsky (URI: University of Rhode Island)H-Index: 19
#2David B. Weishampel (Johns Hopkins University)H-Index: 28
Last.P. Narmandakh (Mongolian Academy of Sciences)H-Index: 1
view all 6 authors...
#1Jingmai K. O'Connor (Los Angeles County Museum of Art)H-Index: 22
#2Luis M. Chiappe (Los Angeles County Museum of Art)H-Index: 45
Last.Alyssa Bell (SC: University of Southern California)H-Index: 4
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#1Frankie D. Jackson (MSU: Montana State University)H-Index: 19
#2John R. Horner (MSU: Montana State University)H-Index: 41
Last.David J. Varricchio (MSU: Montana State University)H-Index: 28
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Cited By13
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#1Vincent Beyrand (European Synchrotron Radiation Facility)H-Index: 2
#2Dennis F. A. E. Voeten (European Synchrotron Radiation Facility)H-Index: 3
Last.Paul Tafforeau (European Synchrotron Radiation Facility)H-Index: 36
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#1Seung Im Choi (SNU: Seoul National University)H-Index: 3
#2Seung Ho Choi (SNU: Seoul National University)H-Index: 18
Last.Yuong-Nam Lee (SNU: Seoul National University)H-Index: 14
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#1Pavel P. Skutschas (SPbU: Saint Petersburg State University)H-Index: 13
Last.Alexander O. Averianov (RAS: Russian Academy of Sciences)H-Index: 23
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#1Fabien Knoll (University of Manchester)H-Index: 15
#2Luis M. Chiappe (Natural History Museum of Los Angeles County)H-Index: 45
Last.Francisco Serrano (UMA: University of Málaga)H-Index: 3
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#1Edina Prondvai (UGent: Ghent University)H-Index: 8
#2Pascal Godefroit (Royal Belgian Institute of Natural Sciences)H-Index: 20
Last.Dongyu Hu (Ministry of Land and Resources of the People's Republic of China)H-Index: 4
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#1Ashley L. Ferguson (ISU: Idaho State University)
#2David J. Varricchio (MSU: Montana State University)H-Index: 28
Last.Alex J. Ferguson (UIdaho: University of Idaho)
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#1Ana Bravo (CSIC: Spanish National Research Council)H-Index: 5
#2Paloma Sevilla (Complutense University of Madrid)H-Index: 9
Last.Fernando Barroso-Barcenilla (Complutense University of Madrid)H-Index: 10
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