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Dickinsonia costata
Dickinsonia costata (after)
Dickinsonia costata was a marine organism from the Ediacaran phase of the Late Precambrian period, dating from 558-555 mya. It is one of a number of enigmatic organisms found in Australia and elsewhere from the Late Proterozoic, known as Vendobionta, that thrived just before most of the known multicellular animal phyla appeared in the fossil record during the Cambrian period.
Dickinsonia, named for Ben Dickinson, a Director of Mines for South Australia, was first found in 1947 by Reginald Sprigs in the Ediacara Member of the Rawnslay Quartzite in the Flinders Range of South Australia. Based on its form, it was first informally grouped with jellyfish-like organisms. It belongs to the kingdon Animalae, the phylum Proarticulata, the class Dipleurozoa, and the family Dickinsoniidae. Other examples have been found in the Mogilev Formation of the Dniester River Basin in Podolia, Ukraine, and in the Lyamtsa and Verkhovkaa Formations in the White Sea area.
Dickinsonia could move along the sea floor, as evidenced by its association with
trackways likely produced by feeding. However, it lacks any convincing
evidence for a mouth, anus, or gut, and appears to have fed by
absorption on its bottom surface. These ovoid-shaped organisms range
from a few mm to 1.4 m in length. They are bilaterally symmetrical, consisting of a number of rib-like segments emerging from a
central groove or ridge, separated by thin
ridge or groove along the axis of symmetry into right and left
halves. Some fossils appear to preserve internal
anatomy, believed to represent a tract that both digested food and
distributed it throughout the organism.
References:
Sprigg, R.C. 1947. Early Cambrian (?) Jellyfishes from the Flinders Ranges, South Australia. Trans. Roy. Soc. S. Aust. 71: 212–24.
Glaessner, M.F.and M. Wade 1966. The late Precambrian fossils from Ediacara, South Australia. Palaeontology 9 (4): 599.
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