Ontogenetic stages in the long bone histology of sauropod dinosaurs
Ontogenetic stages in the long bone histology of sauropod dinosaurs
复制标题
蜥脚类恐龙长骨组织学的个体发育阶段
作者：
N. Klein;M. Sander
摘要长骨（股骨、肱骨）是蜥脚类恐龙最丰富的化石。他们的长度是一个很好的代理体长和体重，其组织学是关于个体发育年龄的信息。在这里，我们提供了几个蜥脚类动物类群，包括梁龙类（迷惑龙，梁龙，不确定的梁龙亚科从Tendaguru层和莫里森形成），基础macronarians（圆顶龙，腕龙，欧罗巴龙）和泰坦龙（Ampelosaurus）的生长系列的组织学变化的比较评估。共采集了167块长骨，主要是肱骨和股骨，以及18块肢带骨。在规定的位置在中间轴钻芯取样，并确认了13个组织学个体发育阶段（HOS阶段）。由于所有蜥脚类动物的长骨的生长是相当均匀的，层状纤维板层骨是主要的组织，HOS阶段可以在不同的分类群中识别，尽管有微小的差异。组织学个体发育阶段通常与身体大小密切相关，因此提供了一种手段来解决重要的问题，如可疑标本的个体发育状态。我们假设性成熟是在HOS-8时达到的，远早于最大尺寸的达到，但我们没有发现HOS-8之后的性分化生长轨迹。根据HOS阶段，我们在圆顶龙样本中检测到两种形态类型，一种是小的（类型1），另一种是大的（类型2），可能代表不同的物种或两性异形。
Abstract Long bones (femora, humeri) are the most abundant remains of sauropod dinosaurs. Their length is a good proxy for body length and body mass, and their histology is informative about ontogenetic age. Here we provide a comparative assessment of histologic changes in growth series of several sauropod taxa, including diplodocids (Apatosaurus, Diplodocus, indeterminate Diplodocinae from the Tendaguru Beds and from the Morrison Formation), basal macronarians (Camarasaurus, Brachiosaurus, Europasaurus), and titanosaurs (Phuwiangosaurus, Ampelosaurus). A total of 167 long bones, mainly humeri and femora, and 18 limb girdle bones were sampled. Sampling was performed by core drilling at prescribed locations at midshaft, and 13 histologic ontogenetic stages (HOS stages) were recognized. Because growth of all sauropod long bones is quite uniform, with laminar fibrolamellar bone being the dominant tissue, HOS stages could be recognized across taxa, although with minor differences. Histologic ontogenetic stages generally correlate closely with body size and thus provide a means to resolve important issue like the ontogenetic status of questionable specimens. We hypothesize that sexual maturity was attained at HOS-8, well before maximum size was attained, but we did not find sexually differentiated growth trajectories subsequent to HOS-8. On the basis of HOS stages, we detected two morphotypes in the Camarasaurus sample, a small one (type 1) and a larger one (type 2), presumably representing different species or sexual dimorphism.