Internal Structure of Cambrian Fossil Embryo Markuelia Revealed in the Light of Synchrotron Radiation X-ray Tomographic Microscopy |
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| Authors: | CHENG Gong PENG Fan DUAN Baichuan and DONG Xiping |
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| Institution: | 1 School of Earth and Space Sciences, Peking University, Beijing 100871, China; 2 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China,1 School of Earth and Space Sciences, Peking University, Beijing 100871, China; 2 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China,1 School of Earth and Space Sciences, Peking University, Beijing 100871, China; 2 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China and 1 School of Earth and Space Sciences, Peking University, Beijing 100871, China; 2 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China |
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| Abstract: | In the light of Synchrotron Radiation X‐ray Tomographic Microscopy (SRXTM), the internal structure of Markuelia hunanensis is revealed. In one example, vitrification and peeling show the annuli hidden under the chorion. Sectioning and 3‐D reconstruction display an intact digestive tract from the inverted introvert to the terminal anus. The inverted introvert forms a rugby cavum. The following digestive tract is rope‐like coiling, parallel to the body axis, about 650 μm in length, and uniform in diameter (～80 μm). An exquisitely preserved pipe‐like structure is hidden in the middle of the rope‐like structure, diameter 20–40 μm, with a length of ～120 μm. We interpret this pipe‐like structure as the possible epidermis of the gut and its surroundings as the possible residue of musculature, similar to that in Priapulans. The two symmetrical rod‐shape structures connecting the body wall and digestive tract are interpreted as the possible retractor muscles. After comparing the well preserved Left‐form and Right‐form Body of Markuelia, we suggest that they may represent a dimorphism. Counted directly, one sample of Markuelia hunanensis possesses 62 annulations and the other 68. |
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| Keywords: | Markuelia Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) dimorphism |
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