Slime has been present on Earth for a very long time — nearly 2 billion years, according to a recent reassessment of fossil evidence.
In a study published this month in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, UO geologist Greg Retallack and Xuegang Mao of China's Fujian Normal University confirm that a fossil from Western Australia is the planet's oldest known land-dwelling slime mold.
The fossil in question, Myxomitodes stirlingensi, is a hairpin-shaped trace of biological activity found in the rocks of the Stirling Range, a mountainous region 200 miles southeast of Perth. Long the subject of scholarly controversy, the fossil has sparked debates both about the specific life form it represents as well as its paleoenvironment.
"They have been interpreted as trails of metazoan animals and often as marine organisms," said Retallack, who is director of the Condon Fossil Collection at the Museum of Natural and Cultural History. "Though they resemble animal trails they probably weren't. Slime molds make similar trails but lack any animal organization: no mouth, no gut, no anus, no nerves, no veins. And we are seeing these fossils on the surface of ancient terrestrial soils , making them additional evidence of life on land during the Paleoproterozoic Period. "
Retallack said that while slime molds are not multicellular in themselves, they may hold important clues about how multicellular organisms evolve.
"Myxomitodes were amoebae that live dispersed in the soil, but these traces of their movement demonstrated that they could coalesce into a slug that wandered over the soil as a unit, possibly providing better feeding opportunities or sporulate, and then disaggregate once again. into single cells, "he said. "This may represent an early stage in the evolution of multicellular creatures, bridging the gap between microbes and more complex life forms."
Thin layers of sediment point to the early arrival of life on land
Gregory J. Retallack et al. Paleoproterozoic (ca. 1.9 Ga) megascopic life on land in Western Australia, Palaeogeography, Palaeoclimatology, Palaeoecology (2019). DOI: 10.1016 / j.palaeo.2019.109266
Ancient fossils reveal fresh clues about early life on land (2019, October 10)
retrieved 10 October 2019
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