贵州盘州中三叠世Mixos...前肢形态差异及种内变化探讨_周敏.pdf

收稿日期:2021-11-11;改回日期:2022-08-31;录用日期:2022-09-02*国家自然科学基金(41372016,41402014,42172008,40920124002,41920104001)、贵州省科技计划项目(黔科合2016支撑 2904 号)、科技部项目(2016YFC0503301)、中科院南京地质古生物研究所现代古生物学与地层学国家重点实验室开放基金(123107,143108)、高校博士点基金(20120001110072)、安徽省自然资源厅科技项目(2021-k-13)和安徽省公益性地质工作项目(2021-g-2-16)联合资助。*通讯作者:周敏,工程师,e-mail: 古生物学报,61(4):643653(2022年12月)Acta Palaeontologica Sinica,61(4):643653(December 2022)研究论文 DOI:10.19800/ki.aps.2021064 贵州盘州中三叠世Mixosaurus panxianensis(盘县混鱼龙)前肢形态差异及种内变化探讨*周 敏1*江大勇1 Ryosuke Motani 2 鲁 昊3 1 北京大学地球与空间科学学院与地质博物馆,北京 100871;2 Department of Earth and Planetary Sciences,University of California Davis,Davis,CA 95616-8605,U.S.A;3 北京师范大学历史学院,北京 100091 提要 混鱼龙科除Mixosaurus cornalianus之外的其他属种由于化石材料稀少、保存破碎,此前对其形态解剖学特征,特别是前肢形态结构特征及其生长发育过程和种内差异认识存在局限。经对发掘自贵州省盘州市(原为盘县)新民乡及邻区多件不同大小的Mixosaurus panxianensis标本前肢进行观察对比和定量研究,发现其尺骨、桡腕骨、指骨以及豌豆骨显示了一定的随生长发育而发生的特征变化。此外,桡骨前缘凹口和中间腕骨近端凹口的发育状态在M.cornalianus及M.panxianensis中均存在种内变异。关键词 混鱼龙 生长发育 中三叠世 贵州 盘州 中文引用 周敏,江大勇,Ryosuke Motani,鲁昊,2022.贵州盘州中三叠世Mixosaurus panxianensis(盘县混鱼龙)前肢形态差异及种内变化探讨.古生物学报,61(4):643653.DOI:10.19800/ki.aps.2021064 英文引用 Zhou Min,Jiang Da-yong,Motani Ryosuke,Lu Hao.Morphological differences and intraspecific variations of the forefins of Mixosaurus panxianensis from the Middle Triassic of Panzhou,Guizhou.Acta Palaeontologica Sinica,61(4):643653.DOI:10.19800/ki.aps.2021064 Morphological differences and intraspecific variations of the forefins of Mixosaurus panxianensis from the Middle Triassic of Panzhou,Guizhou ZHOU Min1,JIANG Da-yong1,MOTANI Ryosuke2,LU Hao3 1 Department of Geology and Geological Museum,Peking University,Beijing 100871,China;2 Department of Earth and Planetary Sciences,University of California Davis,Davis,CA 95616-8605,U.S.A;3 School of History,Peking Normal University,Beijing 100091,China Abstract The anatomy of the forefins of Mixosauridae,including ontogenetic and intraspecific variations,remains poorly known due to the lack of well-preserved materials except for Mixosaurus cornalianus.Several specimens of Mixosaurus panxianensis in different sizes excavated from Panzhou City,Guizhou Province were studied.The result shows some ontogenetic variations in their ulnae,radialia,phalanges and pisiforms.Moreover,the development of the notches on the anterior margin of radius and the proximal margin of intermedium is variable within individuals of Mixosaurus panxianensis.Key words Mixosaurus,Ontogeny,Middle Triassic,Panzhou,Guizhou 644 古 生 物 学 报 61 卷 SUMMARY Mixosaurs were globally distributed during the Middle Triassic.The diagnosis of each species of Mixosauridae is largely based on the differences on the skull osteology,especially on the teeth.However,our knowledge on the post-cranial skeleton is poor.The abundant specimens of Mixosaurus cornalianus led to some preliminary studies of the morphological variations and ontogeny of its forefins(Callaway,1997;Maisch and Matzke,1998).However,detailed anatomical description and study on the morphological variations and ontogeny of other species within Mixosauridae have been limited due to the relative rarity of specimens and their poor preservation.Mixosaurus panxianensis was reported from the Middle Triassic of South China(Jiang et al.,2006).We aimed at discussing the ontogenetic variations on the forefins of M.panxianensis through qualitative and quantitative analyses and comparing them with those of M.cornalianus.Seven specimens of Mixosaurus panxianensis were studied and compared with M.cornalianus,together with other species of Mixosauridae.These specimens can be assigned to M.panxianensis based on the diagnostic features of the skull and forefins(Jiang et al,2006).The morphometric plots of ulna length vs.intermedium anteroposterior length of Mixosaurus panxianensis indicate a growth series.The data of GMPKU-P-1065 is outside the growth series,and this excursion is beyond the purpose of this work,and is not discussed in detail here.There are some morphological variations corresponding with the skeleton size within these specimens.In the smallest individual,there is a notch on the posterior margin of the ulna.The notch is absent in other larger specimens.Two notches on the anterior margin of the radius are present in all specimens,however,they appear deeper in smaller specimens(GMPKU-P-1038 and P-1008).There are two pisiforms in the holotype,but in the smallest specimen,only one pisiform is present.This is probably because the distal pisiform has yet to be ossified.Similarly,the notch on the proximal margin of the intermedium is deeper in smaller individuals.The carpal elements of the smallest specimen,GMPKU-P-1038,are more rounded in shape.However,those of larger individuals are closely packed,and the radiale is widened anteroposteriorly.Moreover,there are 5-6 phalanges per digit in the smallest individual.Compared with the 8-9 phalanges per digit in a larger individual(GMPKU-P-1008),the distal phalanges are probably unossified.A study on the forefins of Mixosaurus cornalianus,which are stor