• A synopsis of Paleocene stratigraphy and vertebrate paleontology in the Qianshan Basin, Anhui, China

    分类: 生物学 >> 动物学 提交时间: 2017-11-07 合作期刊: 《古脊椎动物学报》

    摘要:The Mesozoic and Cenozoic redbeds in the Qianshan Basin comprise a set of monocline clastic rocks and are subdivided into the Late Cretaceous Gaohebu Formation, the Paleocene Wanghudun Formation (including the Lower, Middle, and Upper members) and Doumu Formation (including the Lower and Upper members). Continuous investigations in the Qianshan Basin since 1970 have resulted in discovery of a lot of vertebrate specimens. Up to date, 61 species (including 9 unnamed ones) in 45 genera of vertebrates, representing reptiles, birds and mammals, have been reported from the Paleocene of the Qianshan Basin. Among them, mammals are most diverse and have been classified into 46 species (7 unnamed) of 33 genera, representing 16 families in 10 orders. According to their stratigraphic occurrence, seven fossiliferous horizons can be recognized in the Qianshan Paleocene. Based on the evidence of mammalian biostratigraphy, the strata from the Lower Member through the lower part of the Upper Member of Wanghudun Formation could be roughly correlated to the Shanghu Formation of the Nanxiong Basin (Guangdong Province) and the Shizikou Formation of the Chijiang Basin (Jiangxi Province), corresponding to the Shanghuan Asian Land Mammal Age (ALMA). Both the upper part of the Upper Member of Wanghudun Formation and the Doumu Formation could be correlated to the Nongshan Formation of the Nanxiong Basin and the Chijiang Formation of the Chijiang Basin, corresponding to the Nongshanian ALMA. Paleomagnetic results from several Chinese Paleocene basins suggest that the Shanghuan is roughly correlative to the Puercan and Torrejonian North American Land Mammal Ages (NALMA), while the Nongshanian correlative to the early to middle Tiffanian (Ti1–4a). The Shanghuan and the Nongshanian are probably correlated to the Danian and the Selandian of the Global Geologic Time Scale. Therefore, all the fossil vertebrates collected in the Qianshan Basin are the Early and Middle Paleocene in age.

  • Synchrotron X-ray tomographic microscopy reveals histology and internal structure of Galeaspida (Agnatha)

    分类: 地球科学 >> 地质学 提交时间: 2017-08-29 合作期刊: 《古脊椎动物学报》

    摘要:Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) is a powerful non-destructive method in paleontology, providing ultra-high-resolution 3D insights into the internal structure of fossils. Employing SRXTM, the skull specimens of Shuyu zhejiangensis, a 428 million-year-old galeaspid from the Silurian of Changxing, Zhejiang Province, are investigated. The subsequent analyses indicate that the endoskeletal skull of S. zhejiangensis is composed wholly of cartilage without convincing evidence for the presence of perichondral bone. The cranial anatomy of S. zhejiangensis are unusually preserved in three dimensions largely due to the non-random decay of the cartilaginous braincase and its connecting ‘soft’ tissues. Using Amira or Avizo software, seven virtual 3D endocasts of the skull of S. zhejiangensis were created revealing the gross internal cranial anatomy of galeaspids in great detail for the first time. The preliminary results indicate that during evolution the galeaspid head experienced a fundamental reorganization resulting in the development of jaws. 同步辐射X射线断层显微成像已经成为古生物研究中一种新的重要手段,能够在不损坏化石的前提下,提供化石内部超高分辨率的三维成像。利用瑞士光源最先进的同步辐射X射线断层显微成像技术,研究分析了七个采自浙江长兴志留系(约4.28亿年前)的早期盔甲鱼类浙江曙鱼三维立体保存脑颅化石。同步辐射X射线显微成像结果显示:盔甲鱼脑颅完全由软骨组成,并没有软骨外成骨存在的证据;盔甲鱼脑颅解剖结构能够被精细的保存下来,很大程度上归功于脑颅软骨与周围软组织在埋藏过程中的异时分解。利用AMIRA或AVIZO等计算机三维虚拟复原软件,三维虚拟复原了七个曙鱼脑颅模型,首次揭示出盔甲鱼脑颅内部详细的解剖结构。初步研究结果显示盔甲鱼的脑颅已经发生了显著的重组,具备了颌发育所必需的先决条件。