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Shuhai Xiao

Parapandorina - 5/19/2010

Video:

Cube Section Video

A cube section video of the fossil.


Plane Section Video

A video in which a planar section has been taken of the fossil to expose the cell walls on two sides.


Axial Section Movie

A clip showing the axial slices of the fossil from bottom to top.


Scan Data

The DICOM files for this scan:

Click Here to Download

The BIN files for this scan:

Click Here to Download






 

 
 
 
 

 
    Scanner Settings             
 
 Machine Xradia microXCT
Binning
2
Source Setting
50 kv, 160 µA
Source Distance
23 mm

Detector Distance

9 mm

Pixel Size
.9682 µm

 FOV .954 mm
Magnification 20.093 X
 Exposure Time 6 s
Image Size
 985 X 985








Summary

Researchers at Virginia Tech believe that this Parapandorina fossil is the oldest evidence of any animal life form. CT scanning was particularly useful in the analysis of this fossil because it offered a nondestructive means of seeing the fossil's subcellular structures. Other methods, such as the use of an electron microscope, required that layers be shaved off the fossil to reveal the cellular structures inside. 

Subject

The fossil is from the 600 million year old Doushantuo formation in China. 
Interpretations of the embryo vary, but Virginia Tech researchers believe that it is an animal embyro which would make it the earliest evidence of animal life on the planet. This specific embroyo has multiple  cells with subcellular structures that can be revealed using filters on the CT machine's reconstruction algorithm.  


About the Scan

The subject was mounted on a FIB needle, the tip of which is about 200 microns in diameter. The fossil was very fragile, making it very difficult to mount without breaking. The fragility of the fossil further attests to the advantages of using nondestructive CT scanning over other methods which destroy the subject and give no chance to repeat the imaging procedure.  

Links and Literature

Hagadorn, J. W., S. Xiao, P. C. J. Donoghue, S. Bengtson, N. J. Gostling, M. Pawlowska, E. C. Raff, R. A. Raff, F. R. Turner, C. Yin, C. Zhou, X. Yuan, M. B. McFeely, M. Stampanoni, and K. H. Nealson, Cellular and subcellular structure of Neoproterozoic embryos. Science, 314: 291�294.

Dr. Xaio's website


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