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Nimbia occlusa


Abstract

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Keywords: yyy

Introduction

Nimbia occlusa is a form-taxon comprising flat, discoidal, circular to oval organisms preserved in positive hyporelief. The peripheral part forms a single thick marginal rim. The central portion within the rim is usually smooth and featureless but may have a central tubercle (translated and abridged from Fedonkin 1985 by Hagadorn & Waggoner 2000).

Their consistent morphology and size suggests that they are body fossils. However, identification of these and similar circular "medusoid" fossils is problematic owing to the abundance of circular dubiofossils during this interval (Cloud 1960; Cloud 1968; Hagadorn & Waggoner 2000).

Although it is usually interpreted as a cnidarian, Nimbia occlusa seems unlikely to be a single taxon. If it were, its stratigraphic range of ~100 Ma would be extraordinary.

 
 

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Morphology

Phylogeny and Evolution

Affinities

Fossil Record

Origins

Evolution

Extinction

Systematics

Phylum Cnidaria Hatschek 1888

Class unknown

Order unknown

Family unknown

Genus Nimbia Fedonkin 1980 (verify)

Nimbia occlusa Fedonkin 1980

Original Diagnosis: xxx

Description: Comprising flat, discoidal, circular to oval organisms preserved in positive hyporelief. The peripheral part forms a single thick marginal rim. The central portion within the rim is usually smooth and featureless but may have a central tubercle (translated and abridged from Fedonkin 1985 by Hagadorn & Waggoner 2000).

Larger specimens can be up to 60 mm in diameter, with 10 mm thick rim and slightly raised edges. The centre of the discs is typically either slightly sunken or slightly raised. They are also found preserved in negative epirelief, when the relief is reversed from Fedonkin’s description; in particular, the rim is sunken. The apparent distortion visible in some specimens (fig. 7B, uppermost specimen) suggests that they represent flexible objects.

Occurrence: xxx

Discussion: xxx

 

Conclusion

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Further Information

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References

Cloud 1960

Cloud 1968

Fedonkin 1985

Hagadorn & Waggoner 2000


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