New Papers

Structure, Orientation and Finite Element Analysis of the Tail Club of Mamenchisaurus hochuanensis

Xing, Li-da1)*, Ye, Yong2), Shu, Chun-kang2), Peng, Guang-zhao2), & You, Hai-lu1)
1, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, P. R. China
2, Zigong Dinosaur Museum, Zigong, 643013, P. R. China

The structure and orientation of the posterior extremity of the caudal vertebrae (tail club) of Mamenchisaurus hochuanensis has been studied by Ye et al. 2001 and Ouyang and Ye 2002. This research describes the structure of the tail club of M. hochuanensis ZDM0126 in detail, analysis its function using Finite Element Analysis. The result supports the conclusion that the cranial end of the tail club is fixed, connected with the sequence of the caudal vertebrae, the caudal end is free and is the terminal of the caudal vertebrae. The estimate herein is different from the traditional viewpoint towards the tail club orientation of M. hochuanensis. Further it is determined that the tail club is more efficient in swinging from left to right than up and down; the best region for the tail club to impact is the region of C2 spine. The maximum load for impact is 450N. Based on the articulation form of the tail club and the feature of enlarged neural foreman, this paper confirms that the tail club of ZDM0126 has limitations as a defense weapon, and is more possibly a sensory organ to improve the nerve conduction velocity to enhance the capacity for sensory perception of the surroundings.

Key words:
Mamenchisaurus, Tail Club, Finite Element Analysis, Shangshaximiao Formation, Upper Jurassic

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Mamenchisaurus hochuanensis VS. Yangchuanosaurus (By Zhang zhognda)


Aerodynamic Characteristics of the Crest with Membrane Attachment on Cretaceous Pterodactyloid Nyctosaurus

1*, WU Jianghao2*, LU Yi2, LÜ Junchang1 and JI Qiang1
1 Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037
2 School of Transportation Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083

Abstract: The Nyctosaurus specimen KJ1 is reconstructed under the hypothesis that there is a membrane attached to the crest, the so-called headsail crest. The aerodynamic forces and moments acting on headsail crest are then analyzed. It is shown that KJ1 might adjust the angle of the headsail crest relative to the air current as one way to generate thrust (one of the aerodynamic forces, used to overcome body drag in forward flight) and that the magnitude of the thrust and moment could vary with the gesture angle and the relative location between the aerodynamic center of headsail crest and body’s center of gravity. Three scenarios are tested for comparison to each other: the crest with membrane attachment, the crest without membrane attachment and the absence of cranial crest. It is shown that the aerodynamic characteristics (increasing, maintaining and decreasing thrusts and moments) would almost disappeared in flight for the crest without membrane attachment and none existent without the cranial crest. It is suggested from aerodynamics evidence alone that Nyctosaurus specimen KJ1 had membrane attached to the crest and used this reconstructed form for auxiliary flight control.

Key words: aerodynamic forces and moments, flight dynamics, Nyctosaurus, headsail crest

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Nyctosaurus KJ (illustration by Chuang Zhao and Lida Xing)


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