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1. chinaXiv:201708.00328 [pdf]

Taxonomic reassessment and phylogenetic test of Asiatosuchus nanlingensis Young, 1964 and Eoalligator chunyii Young, 1964

WU Xiao-Chun; LI Chun; WANG Yan-Yin
Subjects: Geosciences >> Geology

The present paper revalidated Asiatosuchus nanlingensis Young, 1964 and Eoalligator chunyii Young, 1964 in taxonomy based on a detailed comparative study on those relevant specimens. New information derived from this study revealed that A. nanlingensis and E. chunyii were truly distinguishable from each other and therefore, diagnosis was further revised for each of them. A. nanlingensis is large, with a moderately long or a very elongate snout, and characterised mainly by the combination of the following characters such as: the quadrate with a lateral condyle much larger than the medial one, the surangular pinched off before reaching the end of the retroarticular process, the dental margins (at least the posterior portion) of the jaws nearly straight, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. E. chunyii is a median-sized, short-snouted animal and characterised mainly by the combination of the following characters such as: the condyles of the quadrate similar in size, the dental margins of the jaws strongly concavo-convex, the dentary symphyses very short, the splenial not entering the mandibular symphysis, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. With new information derived from this study, the phylogenetic relationships of A. nanlingensis and E. chunyii were tested, which did not support the view that the two species formed a monophyletic clade and opposed that E. chunyii could be considered as the synonym of A. nanlingensis. 根据对有关标本的详细对比研究,重新评估了南岭亚洲鳄(Asiatosuchus nanlingensis Young, 1964)和存义始猛鳄(Eoalligator chunyii Young, 1964)的分类。获得的新信息表明这两种是可以彼此区分的,因此对它们各自的鉴定特征进行了进一步修订。南岭亚洲鳄是个大型种类,它很可能具有中等或很长的吻部(眶前段), 主要由以下一些特征组合界定:方骨外髁比内髁大很多,上隅骨在反关节突近端尖灭,上、下颌齿缘(至少后段)几近平直,以及在下颌关节窝外侧上隅骨表面具一凹或纵沟。存义始猛鳄是个中型种类,主要可以由下列特征组合界定:方骨内、外关节髁大小几近相当,上、下颌齿缘强烈凹凸不平,齿骨联合很短,夹板骨不进入下颌联合,以及在下颌关节窝外侧上隅骨表面具一凹或纵沟。根据新的信息对南岭亚洲鳄和存义始猛鳄原来的系统关系进行了检验,所得结果不支持南岭亚洲鳄和存义始猛鳄可以形成一单系分支及反对后者是前者的同物异名。虽然本文研究表明南岭亚洲鳄可以和其他种类区分,但是在系统关系上却不能和亚洲鳄典型种(葛氏亚洲鳄Asiatosuchus grangeri)归于同一支系,如此应该为其建立一属。然而,鉴于南岭亚洲鳄标本太不完整,在没有新的、更完整的标本发现之前,本文仍沿用其原名,如德国亚洲鳄(Asiatosuchus germanicus)一样,后者也不和亚洲鳄典型种归于同一支系。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits1243Downloads531 Comment 0

2. chinaXiv:201708.00183 [pdf]

New information on Dianmeisaurus gracilis Shang & Li, 2015

SHANG Qing-Hua; LI Chun; WU Xiao-Chun
Subjects: Geosciences >> Geology

Dianmeisaurus gracilis is restudied on the basis of a new specimen. It provides some new information, especially that on the skull roof, to the species. The most striking of those new characters include the snout (preorbital region) shorter than the orbit, the interorbital septum extremely narrow, the frontal with a sharp process at both ends, and the posterior margin of the skull roof deeply V-shaped. A phylogenetic analysis with new information confirms that Dianmeisaurus is the sister group of Diandongosaurus and that these two genera, together with those Chinese taxa (Majiashanosaurus, Dianopachysaurus, Keichousaurus, and Dawazisaurus), form a monophyletic clade which is more closely related to the Nothosauroidea than to a clade formed by the European pachypleurosaurs. 根据一件产自云南罗平中三叠世关岭组II段的新标本并结合产自相同地点和地层中的模式标本对纤细滇美龙(Dianmeisaurus gracilis Shang & Li, 2015)进行了详细研究。原模式标本暴露其腹面,而新标本暴露其背面,两者互相补充提供了更完整、精确的纤细滇美龙解剖学信息。新材料揭示该种具有非常短小的吻部,眶前区的长度不仅短于眶后区长度,甚至短于眼眶的长度;外鼻孔小且位置靠前,即鼻孔前区的长度短于鼻孔后缘与眼眶前缘之间的距离;由两额骨构成的眼眶间隔非常狭窄,宽度小于顶骨平台宽度的1/3;额骨前后两端均具渐尖的突起;顶骨后部不收缩,顶骨平台后缘呈深V型。补充了新信息和包含更多属种(如Dawazisaurus)后的系统发育学分析支持了之前滇美龙和滇东龙互为姊妹群的结论,同时它们和马家山龙、滇肿龙、贵州龙和大洼子龙一起构成了一个仅由中国的属种组成的单系类群。与欧洲肿肋龙类群(Dactylosaurus, Anarosaurus, Serpianosaurus和Neusticosaurus)相比,这一单系类群与幻龙类有更近的亲缘关系。

submitted time 2017-08-10 From cooperative journals:《古脊椎动物学报》 Hits661Downloads380 Comment 0

3. chinaXiv:201708.00173 [pdf]

Viviparity in a Triassic marine archosauromorph reptile

LI Chun; Olivier RIEPPEL; Nicholas C. FRASER
Subjects: Geosciences >> Geology

Eggs or embryos have been reported in various groups of fossil reptiles, where viviparity is a common mode of reproduction in aquatic taxa such as the ichthyopterygians, some groups of sauropterygians, mosasauroids, some taxa of choristoderans and certain protorosaurs.Here, we describe a complete embryo of a marine protorosaur, based on a well-preserved, curledup skeleton. The new discovery is referred to a taxon closely related to the remarkable longnecked Dinocephalosaurus. It further confirmed viviparity in an archosauromorph group and indicates an increasing taxonomic diversity not only within this group, but of Triassic marine reptiles in general.

submitted time 2017-08-08 From cooperative journals:《古脊椎动物学报》 Hits512Downloads311 Comment 0

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