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| The new ankylosaurid postcranial specimen (MPC-D 100/1359). in Park, Lee, Currie, ... et Kim, 2021. |
Abstract
A new articulated postcranial specimen of an indeterminate ankylosaurid dinosaur from the Upper Cretaceous (middle-upper Campanian) Baruungoyot Formation from Hermiin Tsav, southern Gobi Desert, Mongolia includes twelve dorsal vertebrae, ribs, pectoral girdles, forelimbs, pelvic girdles, hind limbs, and free osteoderms. The new specimen shows that Asian ankylosaurids evolved rigid bodies with a decreased number of pedal phalanges. It also implies that there were at least two forms of flank armor within Ankylosauridae, one with spine-like osteoderms and the other with keeled rhomboidal osteoderms. Unique anatomical features related to digging are present in Ankylosauridae, such as dorsoventrally flattened and fusiform body shapes, extensively fused series of vertebrae, anteroposteriorly broadened dorsal ribs, a robust humerus with a well-developed deltopectoral crest, a short robust ulna with a well-developed olecranon process, a trowel-like manus, and decreased numbers of pedal phalanges. Although not fossorial, ankylosaurids were likely able to dig the substrate, taking advantage of it for self-defence and survival.
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| The new ankylosaurid postcranial specimen (MPC-D 100/1359). (a) Photograph and (b) line drawing of the specimen in ventral view. (c–e) Skeletal diagram of the specimen in dorsal view (c), left lateral views with dermal armor (d) and without dermal armor (e). Abbreviations: 4os, Type 4 osteoderm; 5os, Type 5 osteoderm; 6os, Type 6 osteoderm; 7os, Type 7 osteoderm; ac, acetabulum; co, coracoid; cof, coracoid foramen; dr, dorsal rib; dv, dorsal vertebra; f, femur; fi, fibula; h, humerus; il, ilium; itp, isolated theropod phalanx; lo, lateral osteoderm; mc, metacarpal; mt, metatarsal; ot, ossified tendon; psr, parasacral rib; ph, phalanx; r, radius; sc, scapula; sr, sacral rib; st, sternal plate; sv, sacral vertebra; t, tibia; u, ulna. Adobe Illustrator CC (version 24.0.1, https://www.adobe.com/kr/products/illustrator.html) was employed to produce (c–e). |
Systematic paleontology
Dinosauria Owen, 1842
Ankylosauridae Brown, 1908
Ankylosauridae, gen. et sp. indet.
Material: MPC-D 100/1359 (Figs. 1, 2, 3), a nearly complete postcranial skeleton that lacks the tail but includes twelve dorsal vertebrae, ribs, pectoral girdles, forelimbs, pelvic girdles, hindlimbs, and free osteoderms.
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| Reconstruction of an ankylosaurid armored dinosaur digging with its forelimbs. Illustration: Yusik Choi. |
Jin-Young Park, Yuong-Nam Lee, Philip J. Currie, Michael J. Ryan, Phil Bell, Robin Sissons, Eva B. Koppelhus, Rinchen Barsbold, Sungjin Lee and Su-Hwan Kim. 2021. A New Ankylosaurid Skeleton from the Upper Cretaceous Baruungoyot Formation of Mongolia: Its Implications for Ankylosaurid Postcranial Evolution. Scientific Reports. 11: 4101. DOI: 10.1038/s41598-021-83568-4
