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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》 Hits935Downloads325 Comment 0

2. chinaXiv:201708.00327 [pdf]

High-precision temporal calibration of Middle Triassic vertebrate biostratigraphy: U-Pb zircon constraints for the Sinokannemeyeria Fauna and Yonghesuchus

LIU Jun; Jahandar RAMEZANI; LI Lu; SHANG Qing-Hua; XU Guang-Hui; WANG Yan-Yin; YANG Jia-Sheng
Subjects: Geosciences >> Geology

Tetrapod assemblages provide a useful means for global correlation of the terrestrial Triassic sedimentary deposits, but currently no reliable temporal framework has been achieved for the Middle Triassic tetrapod assemblages. Here we report U-Pb zircon chemical abrasion–thermal ionization mass spectrometry dates for five volcanic ashes interbedded with vertebrate fossils from the Ermaying and Tongchuan formations of China. Our results support a late Anisian age for the Sinokannemeyeria Fauna and an early Ladinian age for Yonghesuchus Fauna. It is now possible, through biostratigraphic correlation, to provide accurate ages to other Middle Triassic successions such as the Upper Cynognathus Assemblage Zone of the Karoo of South Africa, the Eryosuchus fauna of the Donguz Suite of Russia and the Karamayi Formation of Xinjiang, China. The base of Anisian (Lower/Middle Triassic boundary) should lie below the base of the Ermaying Formation in the Ordos Basin. 四足动物组合带是全球陆相三叠系对比的有力手段,但是迄今为止中三叠世的四足动物组合尚没有可靠的时间框架。本文报道了五个采自二马营组和铜川组,与四足动物化石共同产出的火山凝灰岩样品的锆石化学剥蚀-热电离质谱法年龄。结果表明中国肯氏兽动物群时代为安尼期晚期,而永和鳄的时代为拉丁期早期。通过生物地层对比,这一结果还为其他中三叠世的四足动物组合,如南非的犬颌兽带上部、俄罗斯的引鳄动物群以及新疆的克拉玛依组提供了准确的年龄。鄂尔多斯盆地下中三叠统界线应低于二马营组底界。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits1028Downloads360 Comment 0

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