Abstract: 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 endoskeletalskull 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 Avizosoftware, 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. 

摘要： 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。