Dawazisaurus Brevis, A New Eosauropterygian From the Middle Triassic of Yunnan, China

Dawazisaurus brevis（gen. et sp. nov.） is a newly discovered Triassic marine reptile, represented by a complete skeleton from Member II of the Guanling Formation of Luoping, Yunnan Province, China. This paper aims to（1） present a thorough description of the species,（2） make a detailed comparison to demonstrate if the species can be referred to any known sauropterygian taxa, and（3） conduct phylogenetic analyses to establish the internal relationships of the species with other sauropterygians. In addition, the discovery of Dawazisaurus provides a chance not only to test the phylogenetic patterns of the Sauropterygia obtained by previous studies but also to evaluate the previous hypotheses on the origin of the sauropterygian groups at different levels. D. brevis is an eosauropterygian, characterized by a unique combination of derived features such as a pair of large nasals joining in the formation of the internarial septum, a short trunk with 16 dorsal vertebrae; the zygapophyses of the trunk vertebrae very small or weakly developed; the posterior margin of the skull roof deeply V-shaped, and an ossified distal carpal 5. Phylogenetic analysis indicates that D. brevis appears to be more closely related to the Nothosauroidea than the Pistosauroidea within the Eosauropterygia.

A New Eosauropterygian(Diapsida:Sauropterygia) from the Middle Triassic of Luoping,Yunnan Province

A new eosauropterygian, Largocephalosaurus polycarpon gen. et sp. nov., was described based on a skeleton from the Middle Triassic of Luoping （罗平）, Ynnnan （云南） Province, southwestern China. The new taxon is characterized by a big skull, paired frontal, laterally expanded upper temporal fossa, anterior process of squamosal entering orbit, robust teeth with basally expanded crown and blunt tip, short cervical region, distinctly elongated transverse process of the dorsal vertebrae, short and broad dorsal ribs, stout gastralia, scapula with distinctly posterodorsally extending blade, distinctly robust humerus, eleven carpal ossifications, and a manual fomula of 2-3-4-5-5. A phylogenetic analysis suggests that Largocephalosaurus is the basal-most member of a clade including Wumengosaurus, European pachypleurosaurs, and Nothosauroidea.

云南罗平中三叠世大凹子剖面牙形石生物地层及其沉积环境研究

罗平生物群产出于关岭组二段,该段大凹子精细剖面细致的沉积学描述记录显示,剖面岩性变化趋势为:从生物扰动灰岩到含硅质结核的条带泥晶灰岩(钙屑浊积岩)向白云岩演化。剖面详细的牙形石生物地层研究表明,牙形石带属于Nicoraella kockeli带,同时该带可分两个亚带,即Nicoraella kockeli type 1亚带和Nicoraella kocke-li type 2亚带。牙形石生物地层年代确定在Anisian期的Pelsonian亚期。通过大凹子剖面含牙形石段产出环境分析表明:深灰色具脉状层理含泥质灰岩的开阔台地相沉积环境牙形石产出较少且保存一般,而深黑色纹层状泥晶灰岩段台间盆地相沉积环境中牙形石产出丰富且保持完好。大凹子剖面沉积构造研究表明:罗平生物群产出于台间盆地相钙屑浊流沉积环境。

混鱼龙(爬行动物:鱼龙类)在云南罗平中三叠统的发现

本文首次报导和系统描述了在云南罗平中三叠统关岭组上部发现的混鱼龙Mixosaurus kuhnschnyderi Brinkmann,1998,并与国内外同期地层中已知的混鱼龙种进行了对比。此外,还简单介绍了发现此化石的生物学、地层学和生物古地理分区的意义。

云南罗平上石坎剖面中三叠世层序地层及沉积相分析

在云南罗平上石坎剖面,产罗平生物群的中三叠统关岭组二段出露良好,为灰黑色纹层状含硅质结核、硅质条带泥晶灰岩和具滑塌构造、包卷层理等沉积构造为典型沉积。根据层序地层和沉积相分析,在上石坎剖面划分出2个三级沉积层序(SQ1和SQ2),相对海平面经历了2次升与降的过程,SQ1表现为局限台地—开阔台地—台内盆地—开阔台地的演变过程;SQ2表现为开阔台地—台内盆地—开阔台地—局限的蒸发台地的演变过程。SQ1和SQ2的台内盆地内发育凝缩段,是鱼类和海生爬行类脊椎动物保存的最佳层位。