''Myxomitodes'' (Greek "slime thread like") is a

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of problematic fossil from the Paleoproterozoic (1900 million years old) Stirling Range Formation of Western Australia, and is significant as a very old megascopic fossil, and thus

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

. It is a trace fossil and thus evidence of activity, rather than a body fossil. Stirling Myxomitodes detail

Description

''Myxomitodes stirlingensis'' are irregular markings on the surface of beds, with the superficial appearance of animal trails. They are problematic for such trails because of their great geological age. Unlike fossil trails made by slugs or worms, ''Myxomitodes'' flare and vary in width. Worm and slug trails are long, so generally run off the edges of rock slabs. ''Myxomitodes'' in contrast is short, with one end tapering and the other forming a bulbous structure. Stirling Myxomitodes locality

Biological affinities

''Myxomitodes stirlingensis'' is a problematic fossil of controversial biological affinities. At first it was interpreted as a trail of a soft-bodied worm-like animal, and then as a trail of wind blown bubbles. Later it was suggested to be a trace of a giant globular, marine amoeba, similar to '' Gromia''. Discovery of a variety of paleosols associated with ''Myxomitodes'' suggests that it might have lived on land like dictyostelid slime molds. These are dispersed soil amoebae for most of their life cycle, but occasionally stream together to form a

grex Grex or GREX may refer to: * Grex (biology), a multicellular aggregate of amoeba of the phyla Acrasiomycota or Dictyosteliomycota * Grex (horticulture), (pl. greges) a kind of group used in horticultural nomenclature applied to the progeny of an a ...

, or slug-like multicellular aggregate that moves a short distance to form a sporulating stalk. This explanation explains the flaring shape (from cellular aggregation), levees (from slime trail), short length (migration distance) and bulbous ends (base of sporulating stalk). However, the fossil is older than the oldest currently accepted amoebozoans, bringing this interpretation into doubt.

References

External links

{{Taxonbar, from=Q83853325 Paleoproterozoic Fossils of Australia Controversial taxa Trace fossils