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1. chinaXiv:201709.00121 [pdf]

New fossils of paraceratheres (Perissodactyla, Mammalia) from the Early Oligocene of the Lanzhou Basin, Gansu Province, China

LI Yong-Xiang; ZHANG Yun-Xiang; LI Ji; LI Zhi-Chao; XIE Kun
分类: 地球科学 >> 地质学

描述了在兰州盆地渐新统韩家井组底部的黄砂层中新发现的巨犀化石:黄河巨犀(Paraceratherium huangheense sp. nov.) (新种), 该化石产出层位的古地磁年龄为距今31.5Ma。新种主要特征为:P2之前无齿槽痕迹,一对下门齿粗壮,互相靠近,向前平伸且略微上翘,下颏孔位于p3之下,水平支下缘平直, p2前的齿隙部分向上隆起,下颌角圆钝,上升支后缘斜向后上方,齿式: ?·?·3·3/1·0·3·3。除个体较大、下颌后缘有所不同之外,其下颌的总体特征与巴基斯坦的Paraceratherium bugtiense最为接近,显示两者可能具有较近的亲缘关系。新标本的发现为确定经典的Dera Bugti地点产大巨犀化石层位的年代提供了新的证据,并为青藏高原的隆升讨论提供了新的哺乳动物化石证据。

提交时间: 2017-09-28 来自合作期刊:《古脊椎动物学报》 点击量989下载量312 评论 0

2. chinaXiv:201709.00122 [pdf]

Introduction to terminologies of tooth enamel microstructures and a proposal for their standard Chinese translations

MAO Fang-Yuan; LI Chuan-Kui; MENG Jin; LI Qian; BAI Bin; WANG Yuan-Qing; ZHANG Zhao-Qun; ZHAO Ling-Xia; WANG Ban-Yue
分类: 地球科学 >> 地质学

Tooth enamel is composed of elongated, hexagonal crystallites of hydroxyapatite. Some crystallites are arranged into various regual structures and futher formed a composite structure in a hierarchical manner. The hierarchical system can provide a basis for analysis different levels of structural complexity from varitaiton of particular crystallite strucutes to variation of structural types throughout a individual’s dentition. The size, orientation, distribution and the packing patterns of crystallites are gene-comtrolled and have limited range of intraspecific variability. Thus, these microstructures provide considerable and reliable morphological characters that help understanding of external dental morphology in context of both phylogeny and function in vertebrates. Because teeth are highly resistant to weathering, mainly owing to their enamel covering, so that they were commonly preserved as fossils. This organic system, particularly their microstructures, has attracted more and more attention from vertebrate paleontologists and other morphologists. However, as already recognized by many previous studies, some terminologies of the enamel microstructures have been complex and used inconsistently. Although considerable effort has been made to study enamel microstructures in China during the last few decades, a standard terminology of enamel microstructures in Chinese has not be formally brought into line with that in English literatures. Here we intend to introduce and systematize the relevant terminology used in the study of enamel microstructures and translate them into Chinese, in hoping that this systematic effort will enhance researches of enamel microstructures in China. 脊椎动物牙齿釉质显微结构具丰富的形态学特征,承载着系统发育和生物力学等方面的信息。本文在前人的研究基础上,试图系统地介绍牙釉质显微结构的基本内容,提出牙釉质研究中相关术语的中文译名建议,并对一些重要术语做了简要解释,供相关研究者参考,以期促进牙釉质显微结构研究的进一步发展。

提交时间: 2017-09-28 来自合作期刊:《古脊椎动物学报》 点击量850下载量425 评论 0

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