PRELIMINARY HISTOLOGICAL STUDY ON THE LONG BONES OF MIDDLE JURASSIC SHUNOSAURUS AND OMEISAURUS FROM DASHANPU,ZIGONG,SICHUAN
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Abstract:
The present paper describes the histological features of the long bones of Shunosaurus lii and Omeisaurus tianfuensis from the Dashanpu Dinosaur Fauna in Zigong. There are some similar features in these two dinosaurs as follows: The long bones of the two dinosaurs are composed of the compact bone and cancellous bone. The cortex of the compact bone of the two dinosaurs are fibrolamellar tissues which are composed of primary woven-fibroid and lamellar bone tissues. The cancellous trabeculae are composed of the lamellar bone and with secondary Haversian bones in the lamellar bones. There is an obviously broken cancellous area in the center of the cancellous bone in humerus of the two dinosaurs. The restlines are not found in the long bones of the two dinosaurs. On the other hand, there are some differences in these two dinosaurs as follows: There are no laminar structures in the fibrolamellar bones of the humerus of Shunosaurus lii, but the laminar structures are present in those of Omeisaurus tianfuensis. There is no obvious Haversian bone in the adult humerus of Shunosaurus lii, but it is very obvious in Omeisaurus tianfuensis and its thickness is about the ninety percent of the compact bone. The broken cancellous area in the center of the cancellous bone in humerus of Omeisaurus tianfuensis is much smaller than that of Shunosaurus lii. Through the comparative histological study on the long bones of these two sauropods and other several dinosaurs from the Upper Cretaceous in China, the following results are obtained: The fibrolamellar tissues typical in the compact bones indicate that its long bones had a rapid postnatal growth rate. The growth styles of the dinosaurs belong to the indeterminate growth, it means that the growth is not ceased after they reached adult stage. The rates of deposition are obviouly different in adult dinosaurs. The resorption in the inner part of the bone has more differences in the growth process of the long bones in different dinosaurs. The growth lines have some obvious differences between the different bones or in the growth process of the bones. All the features as mentioned above reveal that the histological features of dinosaurs are very complicated, in which there are some obvious differences between the different dinosaurs or in the adult and juvenile materials of the same dinosaur or the different bones of one individual or the different parts of one bone.
