内蒙古晚白垩世似鸟龙与鸭嘴龙骨组织的研究

HISTOLOGICAL STUDY ON THE LATE CRETACEOUS ORNITHOMIMID AND HADROSAURID

对采获于我国内蒙古二连浩特晚白垩世达布苏组的蜥臀目兽脚亚目似鸟龙科恐龙 (Archaeor nithomimiusasiatcus)和鸟臀目鸟脚亚目鸭嘴龙科恐龙 (Bactrosaurusjohnsoni)的胫骨、腓骨、股骨、尺骨、肋骨、椎骨骨组织结构特征进行了研究 ,并将它们的骨组织与爬行纲初龙亚纲的现存湾鳄 (Crocodylusporosus)和非洲鸵鸟(Struthiocamelus)的骨组织进行直观比较 ,应用计算机图像分析技术及统计方法进行比较研究。结果显示 :1)这两种恐龙的骨组织具有相似的基本结构特征 ,但也存在一些差异 ;2 )两种恐龙的长骨组织均具有快速后生生长特点 ;3)似鸟龙科恐龙的幼年长骨沉积速率高 ,成体则相对减慢 ;4)似鸟龙科恐龙的幼体肋骨中具有生长轮 ,成体的肋骨中则生长轮有可能因骨改建而消失 ;5 )两种恐龙、非洲鸵鸟和湾鳄的长骨的血管分布密度有统计学的显著差异 ,两种恐龙的骨组织血管密度介于非洲鸵鸟和湾鳄之间 ;6 )这两种恐龙的骨组织既不同于现代鸟类骨组织 ,也不同于现代爬行类骨组织 ,有可能是介于这两种骨组织之间的一种独立的过渡类型或中间类型。

The present paper describes the histological aspects of several individual skeletons assigned to two species of Ornithomimidae(Saurichia)、 Hadrosauridae (Ornithischia) (discovered from the Late Cretaceous Iren Dabasu (Erenhot) Formation in Inner Mongolia respectively). It reports the results of comparison between the dinosaur's, the modern reptilian and avian limb bones. The observation on the thin sections of dinosaur's femora, tibias, ulnas, fibulas, ribs and vertebras has revealed their microstructral and histomorphological features. Comparative histological study on the limb bones of the dinosaurs, the modern crocodile ( Crocodylus porosus ) and of the ostrich ( Struthio camelus ) was carried out. An image analysis on the microphotographs of the compact bone of these bone samples by using a computer system was also performed, and yielded the following results: 1. The bone tissues samples of two dinosaurs special do show distinctive difference in general histological characteristics. 2. The long bones of the two dinosaurs have woven fibroid tissue, which signs rapid postnatal growth of bones. 3. The long bones of the juvenile ornithomimid were deposited rapidly,but slow down in adults. 4. The growth rings that are found in the juvenile ornithomimid ribs must be disappeared in adult rib bones. 5. Vascularity (density of vessels) of the leg compact bone of the dinosaurs, the crocodile and the ostrich has been measured by image analysis, it demonstrates that statistically significant differences of vascularity exist among the dinosaurs, crocodile and ostrich, the two dinosaurs have the vascularity values between that of the crocodile and ostrich. 6. The dinosaur bone tissue shows significant difference from that of modern reptile (the crocodile), and that of modern avian (ostrich) bones. Unlike the crocodile, the ornithomimid rib bones have growth rings with fibro lamellar bone tissue. The cancellous of the two dinosaurs has both woven fibroid and lamellar bone tissues. The compact bone of the dinosaurs, like that of the bird ostrich, has primary and secondary osteons, formed by concentric arrangement of bone matrix around blood vessels. In contrast, in the modern reptilian crocodile, blood vessles are rarely located within primary and secondary osteons.It is most likely that dinosaurs have an intermediate pattern of bone microstructure because their physiology was neither typically reptilian nor avian.