冀北辽西中生代晚期鲟形鱼类化石

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	冀北辽西中生代晚期鲟形鱼类化石
	金帆
学位类型	博士
导师	张弥曼
	1998
学位授予单位	中国科学院古脊椎动物与古人类研究所
学位授予地点	古脊椎动物与古人类研究所
关键词	鲟形鱼中生代晚期河北北部辽宁西部古脊椎动物
摘要	本文主要依据近年来采自冀北辽西中生代晚期义县组地层的一批保存颇为完好的鲟类化石新标本，对潘氏北票鲟、丰宁北票鲟、长背鳍燕鲟和刘氏原白鲟的形态特征进行了较为详尽的补充描述。在此基础之上，确认丰宁北票鲟在头长与全长的比例、眶上和眶下感觉管的连接、侧线管小骨的数目以及尾鳍背棘鳞的分布等特征上有别于潘氏北票鲟，前者并非后者的同物异名；发现燕鲟与北票鲟在头骨的形态特征、骨骼的骨化情况以及各鳍的大小等方面的诸多特征上存在明显差异，故而将燕鲟从北票鲟科移至新建的燕鲟科；并重新修订或修正了北票鲟科、匙吻鲟科、北票鲟属、燕鲟属、原白鲟属以及属下各种的特征。北票鲟与软骨硬鳞鱼和鲟科的关系较为密切。目前所知北票鲟、软骨硬鳞鱼和鲟科共有2个特征：1）方颧骨曲棍状或长靴形；2）体侧裸露无齿状鳞片。北票鲟和软骨硬鳞鱼共有3个特征：1）吻短而圆钝，吻部无背腹吻骨片；2）钩状外翼骨尚未与膜质腭骨愈合；3）齿骨外侧后下角有小片状隅骨。北票鲟科和鲟科目前仅发现1个共有特征，即宽大的翼骨板内缘和后缘呈圆弧状，前下缘向内凹入。但就目前的研究程度北票鲟与软骨硬鳞鱼和鲟科的关系仍只能作为未解的三分式分支。燕鲟在鲟形鱼类中仍与北票鲟最为相近，两者共有下列特征：1）吻部仅有环绕感觉管骨化的管状小骨；2）无间锁骨；3）尾上叶背棘鳞纤细；4）尾鳍上的菱形鳞片退化或完全消失。此外，燕鲟与软骨硬鳞鱼和鲟科亦有一些相似特征，如燕鲟和软骨硬鳞鱼的体型较侧扁，翼骨板都很厚大且前下缘圆钝；燕鲟与鲟科则在膜质腭骨、齿骨和舌颌骨的形状上较为相近。原白鲟仅具有匙吻鲟科较为公认的6个特征中的3个：1）有一系列横截面呈圆柱形的细长背腹吻骨片；2）吻骨片两侧有星状小骨；3）颅顶前、后纵窗发育。在匙吻鲟科中，原白鲟可能与古白鲟关系最为相近，两者共有5个特征：1）中间额外肩胛骨；2）上匙骨以宽阔的前背突连接于后颞骨内面；3）下鳃盖骨后部尚未深裂为扇形展布的细长骨棒；4）3-4根方形或长条形的鳃条骨；5）成体的尾鳍外观近呈正型尾。
其他摘要	This thesis gives a detailed redescription of the osteology of Peipiaosteus pani Liu and Zhou 1965, P. fengningensis Bai 1983, Yanosteus longidorsalis Jin et al. 1995, and Protopsephurus liui Lu 1994, based on a series of well-preserved specimens collected from the Late Mesozoic Yixian Formation in northern Hebei and western Liaoning area during the recent years. With this study, it can be confirmed that P. fengningensis is readily distinguishable from P. pani, and that Yanosteus is so different from Peipiaosteus that it maybe belongs to another group of Acipenseriformes, which is named here as Yanosteidae fam. nov. Furthermore, the work provides the emended diagnoses of the families Peipiaosteidae and Polyodontidae, the genera Peipiaosteus, Yanosteus, and Protopsephurus, and the subordinated species as well. This thesis briefly reviews the relationships of Acipenseriformes, especially the phylogenetic position of the genera Peipiaosteus, Yanosteus, and Protopsephurus. With the incorporation of these fossil forms, not a few characters previously considered to be unique or derived to some groups of different categories seems convergent (e.g., loss of opercle), synplesiomorphic (e.g., ventral process of posttemporal), or more restricted (e.g., a peculiarly shaped subopercle with a posteriorly pointing fan of rod-like ossification). In deed "the phylogenetic studies of Acipenseriformes are still in their infancy" (Bemis et al., 1997: p.29). According to the distribution of the known characters, Peipiaosteus and Yanosteus are possibly sister groups, but both of them share some characters with Chondrosteus, Peipiaosteus+Yanosteus, and Acipenseridae remain an unresolved trichotomy. The relationships of Protopsephurus to other forms in Polyodontidae are also problematic, because Protopsephurus shows close relationships with Paleopsephurus, and to less extent with Crossopholis, which is contradictory to the cladogram recently proposed by Grande and Bemis (1996:Fig. 11).
页数	61
语种	中文
文献类型	学位论文
条目标识符	http://119.78.100.205/handle/311034/1830
专题	硕博论文
推荐引用方式 GB/T 7714	金帆. 冀北辽西中生代晚期鲟形鱼类化石[D]. 古脊椎动物与古人类研究所. 中国科学院古脊椎动物与古人类研究所,1998.

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