Finest preparation: Hallucigenia

Positive-plate before preparation

Positive-plate before preparation

Negative side: the marked areas must be transferred to the positive

Negative side: the marked areas
must be transferred to the positive

Size comparison to scalpel blade: precision work

Size comparison to scalpel blade:
precision work

During preparation after successful transfer

During preparation after
successful transfer

The finished specimen, slab is about 16cm wide

The finished specimen, slab is about 16cm wide

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Hallucigenia represents a problematic fossil that is placed to the lobopods. It is characterized by a worm-like body, with spine-like projections on the upper side and tentacle-like extremities on the underside. The present specimen shows one row of appendages on the upper and lower side, whereas the extremities of the lower side are only vaguely preserved. The fossil was found on a positive and a negative plate.

Two areas had to be transferred from the negative to the positive side. For this purpose it was absolutely necessary to transfer the only millimeter-sized parts of the fossil, which are preserved as a wafer-thin aluminum silicate layer, with a perfect fit. In such cases, mistakes in the gluing process can lead to total loss. After successful transfer, the Hallucigenia was exposed using a fine airscribe, needles and scalpel. The last two photos show the finished specimen in close-up with and without alcohol to enhance contrast. In addition to the excellently preserved eye spot, the digestive tract should be mentioned, which can be observed especially at the head end and in the middle part.

The difficult preparation of this outstanding fossil was described in detail in a preparation report for the website steinkern.de: Link to the article.

Fossil: Hallucigenia fortis 

Locality: Anning, Yunnan province (China)

Formation: Lower Cambrian, Maotianshan Slate, Yuanshan Member, Heilinpu Formation

Length of the fossil: 3 cm (1.2 inch)

Collection: Yuxi Wang

Work required: 12 hours