Studies of Dinosaur Bone Histology: Paleobiological Implications

恐龙骨骼包含许多重要的特征，包括纤维板层骨、密集的血管化和次级哈弗氏骨。这些特征在现存的恒温动物中都有发现，并被引用来支持恐龙是吸热动物的概念。最近出现了一种观点，即所有的组织类型都存在于恒温动物和变温动物中。骨的特定组织学类型可能表明生长速率升高。结合其他方法，如骨骼年代学，可能对代谢率有一些了解。通过对津巴布韦两种早侏罗世恐龙Massospondylus carinatus和Syntarsus rhodesiensis的股骨系列的组织学研究，取得了进展。这两种恐龙都有纤维板层骨，但都没有显示出现存恒温动物的所有特征。大脊柱炎的生长年轮表明，它花了15年的时间才达到250公斤的体型。和现代变温动物一样，生长速度是不确定的。它的生长与现存的恒温动物一样稳定，但它需要7年才能达到20公斤的大小。每一种恐龙在恒温动物和异温动物之间的生理连续体上都占据着独特的位置。这项研究将把对津巴布韦恐龙的细致研究扩展到北美和蒙古的三叠纪、侏罗纪和白垩纪恐龙的个体发育系列，以获得恐龙生长速度和恒温动物潜在发展的系统发育、地层和地理视角。

Dinosaur bone contains many significant features including fibro-lamellar bone, dense vascularization, and secondary haversian bone Such features are found in living endotherms, and have been cited as supporting the concept that dinosaurs were endothermic. Recently the view has emerged that all tissue types are found in both endotherms and ectotherms. Specific histological types of bone may indicate elevated growth rate. Combined with other approaches such as skeletochronology, some insight into metabolic rate may be obtained. Progress was made by careful investigation of the histology of series of femora that span the ontogeny of two Early Jurassic dinosaurs from Zimbabwe, Massospondylus carinatus and Syntarsus rhodesiensis. Both dinosaurs show fibrolamellar bone but neither shows all features of living endotherms. Massospondylus shows growth rings that indicate it took 15 years to attain a body size f 250 kg. Growth rate was indeterminate as in modern ectotherms. In Syntarsus growth was determinate as in living endotherms, but it took 7 years to attain the size of 20 kg. Each of these dinosaurs occupies a unique position on a physiological continuum between endothermy and ectothermy. The proposed study will extend the careful techniques worked out on the Zimbabwean dinosaurs to ontogenetic series of Triassic, Jurassic and Cretaceous dinosaurs from North America and Mongolia in order to obtain a phylogenetic, stratigraphic and geographic perspective on dinosaurian growth rates and the potential development of endothermy.