open access

https://doi.org/10.14943/doctoral.k13571

https://hdl.handle.net/2115/91630

モンゴルの白亜系から発見されているオルニトミモサウルス類（恐竜類：獣脚類）の進化、多様性、異質性

英語

2019-03-25

Hokkaido University

xvi, 318p.

Ornithomimidae, the derived clade of Ornithomimosauria, are one of the major clades of coelurosaurian dinosaurs and fossil remains of this group have been richly discovered in the Cretaceous sediments of eastern Asia, specifically in the Gobi Desert of Mongolia. In this study, four ornithomimosaur specimens from the Late Cretaceous of Mongolia are newly described in detail. They include a multitaxic bonebed of two potential new ornithomimosaurs from the Bayanshiree Formation (Cenomanian- Turonian), a new taxon, named Aepyornithomimus tugrikinensis gen. et sp. nov., from the Djadokhta Formation (Campanian), and a complete articulated ornithomimid skeleton from the Nemegt Formation (late Campanian-early Maastrichtian). The ornithomimosaur specimens discovered from the Baishin Tsav locality were collected in a single multitaxic bonebed with a different ontogenetic stage of at least five individuals. This bonebed suggests that it is possible that a small pack (<10 individuals) of multispecific ornithomimid herd was herding together in some preferable places. Aepyornithomimus tugrikinensis gen. et sp. nov. was discovered from the Upper Cretaceous Djadokhta Formation of Mongolia. The phylogenetic position of this new taxon is placed a member of the derived ornithomimosaurs. Hence, it is recovered a missing cap of evolution of the Late Cretaceous Mongolian ornithomimosaurs from the Djadokhta Formation, as well as the first ornithomimid record from eolian influenced environment, indicative of their wide capability to adapt to arid environments. The Upper Cretaceous Nemegt Formation of Mongolia is rich in well-preserved dinosaurs, and ornithomimosaurs are common dinosaurs in the formation. A complete articulated ornithomimosaur skeleton was recovered from the Upper Cretaceous Nemegt Formation of Bügiin Tsav locality, Mongolia. The morphological features and the phylogenetic analysis of this specimen represent as the definitive new ornithomimid and the fourth ornithomimosaur from the formation, demonstrating a high diversification of this group in Late Cretaceous in Asia. Moreover, the structures of manual elements among Nemegt ornithomimosaurs reveals their remarkable diversity. The results of numerical analyses show that a large diversity of manual morphology may be related to large variety of palaeoecological niches were prevailed in the Nemegt ecosystem.

2019-03-25

甲第13571号

博士(理学)

(主査) 准教授 小林 快次（総合博物館）, 教授 中川 光弘, 教授 竹下 徹, 准教授 伊庭 靖弘

理学院（自然史科学専攻）

博士論文

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