山东诸城地区上白垩统的巨型山东龙的形态学、系统发育学和个体发育学研究

In 1973, Prof. Chengzhi Hu formally named and described Shantungosaurus giganteus, which is now widely recognized as the largest ornithischian dinosaur in the world. This taxon is an important representative among Asian hadrosaurines. The material of S. giganteus is known from the middle and lower parts of the Late Cretaceous Wangshi Group of Zhucheng, Shandong Province. Owing to the problematic identifications of type specimens and insufficient collections of anatomical information, the material of S. giganteus still requires further observations and comparative studies. Since 1988, a large number of specimens assigned to Shantungosaurus were collected from outcrop sections of the Wangshi Group in the Zhucheng area. Based on the type specimens and new material of S. giganteus, we will conduct the proposed project that includes supplements and updates of anatomical information and measurements of the taxon, revisions of the phylogenetic topology of Hadrosauridae, and discussions on the definition and validity of Hadrosaurinae. Furthermore, in light of the humeral growth series of S. giganteus, the project will also focus on the ontogeny of the genus and species: (1) reduced major axis regression analyses of log-transformed measurements are utilized to evaluate the allometric patterns of various structures of the humerus; (2) histological characters from the humeral neck are observed under the microscope to infer the development trend of long bone microstructure; (3) data on annual growth rings of complete cross sections from humeral necks of subadult individuals are analyzed to reconstruct the sigmoidal growth curves that can help to explore the reason for the gigantism of this taxon. Two SCI papers are expected out of this research project.

胡承志于1973年命名和描述了世界上已知最大的鸟臀类恐龙—巨型山东龙。它是鸭嘴龙亚科恐龙的亚洲代表。该类群的化石材料产自于山东诸城晚白垩世王氏群的中下部。由于前人对模式标本的鉴定存疑且解剖学信息未被充分地采集，巨型山东龙的化石材料仍有待深入地观察和对比研究。自1988年至今，许多山东龙标本在诸城的王氏群露头剖面中被发现。本项研究将基于巨型山东龙的模式标本和新材料对该类群的解剖学信息和测量数据进行补充和更新，完善鸭嘴龙科的系统发育布局，并讨论鸭嘴龙亚科的定义和有效性。此外，我们还将基于巨型山东龙的肱骨生长系列开展个体发育学研究，包括(1)对线性测量数据的对数值执行简化主轴回归分析以评估肱骨各结构的异速生长模式，(2)借助于肱骨颈的组织学特征推测长骨微观结构的发展趋势，以及(3)根据亚成年个体的完整肱骨颈切片的年度生长轮数据重建S形生长曲线，讨论该属种大型化的原因。预期发表SCI论文2篇。

通过详尽的全球鸭嘴龙类化石材料的骨学对比研究，全面展示了巨型山东龙(Shantungosaurus giganteus)的形态学特征信息和数据，进而修订了该属种的鉴定特征。基于最大简约法的支序分析结果显示：鸭嘴龙亚科作为赖氏龙亚科的姐妹群，是一个有效的分类单元；在鸭嘴龙亚科内部，Edmontosaurini被看作是包含Kerberosaurus和Edmontosaurus在内的最小单系类群，并且暂时由4个属组成；Edmontosaurus和Shantungosaurus构成了姐妹群；Edmontosaurus和Shantungosaurus共同构成的支系位于Edmontosaurini靠近冠部的位置。S. giganteus的肱骨三角胸嵴在个体发育过程中经历了强烈的前外侧扩展与形状变异。针对这一类群肱骨线性测量属性的简化主轴回归分析得到了相似的结论：因变量“肱骨在三角胸嵴处的最大近远长度”和“肱骨在三角胸嵴处的最大内外宽度”相对于肱骨的全长均展示了轻微的积极异速生长；回归直线异速系数略大于Maiasaura peeblesorum、Edmontosaurus regalis和Amurosaurus riabinini回归直线的对应系数。在微观形态方面，S. giganteus肱骨的组织学形态经历了明显的个体发育变化：例如，初级骨单位的血管形状由近圆形和近椭圆形向层状和树枝状转变；骨基质从编织纤维骨向平行纤维骨和层状骨转变；生长轮年度间隔值沿离心方向展示了变小的趋势。课题组基于肱骨颈横截面的组织学数据建立了S. giganteus年龄和体重之间的多模式S形生长曲线。在假定年度生长轮最小数量的骨龄框架下，Gompertz模式的S形曲线方程具有较小的赤池信息准则值，展示了较高的拟合度。因此，这一模式和其曲线方程被考虑为反映年龄和体重之间非线性关系的最佳选项。根据最佳的S形生长曲线方程估算，初始性成熟年龄为10–12岁；这一属种在曲线拐点处的最大生长速率接近于一些大型蜥脚类属种的对应速率，达到了2.3千克/天。S. giganteus体重在幼年晚期至亚成年早期阶段的急剧增长很可能导致了这一类群的身体大型化发展。