The fossil, dating from 560 million years ago, was discovered in Newfoundland, Canada. On the basis of its four-fold symmetry, morphological characteristics, and what appear to be some of the earliest impressions of muscular tissue, researchers from the University of Cambridge, in collaboration with the University of Oxford and the Memorial University of Newfoundland, have interpreted it as a cnidarian: the group which contains modern animals such as corals, sea anemones and jellyfish. The results are published today (27 August) in the journal Proceedings of the Royal Society B.
The new fossil, named Haootia quadriformis, dates from the Ediacaran Period, an interval spanning 635 to 541 million years ago. It differs from any previously described Ediacaran fossil, as it comprisesof bundles of fibres in a broadly four-fold symmetrical arrangement: a body plan that is similar to that seen in modern cnidarians.
As the Abstract puts it, the difference between this and other Ediacarans seems to be “Haootia is distinct from all previously published contemporaneous Ediacaran macrofossils in its symmetrically fibrous, rather than frondose, architecture.” In short, it does not look like a plant. Here are more typical Ediacarans:
But if this is part of the cnidarian group, and dated at 560 years ago, there is a comb jelly ancestor dated at 600 million years old.
See also: Genome map shows comb jellies had separate course of evolution from other animals
Core muscle proteins are present in sponges that lack true muscles
It sounds as though we don’t know enough yet about the animals of this era. For example, in the Abstract below, the find is referred to as “ Haootia quadriformis n. gen., n. sp.” Which means we do not yet know how it should be classified.
Here’s the abstract:
Muscle tissue is a fundamentally eumetazoan attribute. The oldest evidence for fossilized muscular tissue before the Early Cambrian has hitherto remained moot, being reliant upon indirect evidence in the form of Late Ediacaran ichnofossils. We here report a candidate muscle-bearing organism, Haootia quadriformis n. gen., n. sp., from approximately 560 Ma strata in Newfoundland, Canada. This taxon exhibits sediment moulds of twisted, superimposed fibrous bundles arranged quadrilaterally, extending into four prominent bifurcating corner branches. Haootia is distinct from all previously published contemporaneous Ediacaran macrofossils in its symmetrically fibrous, rather than frondose, architecture. Its bundled fibres, morphology, and taphonomy compare well with the muscle fibres of fossil and extant Cnidaria, particularly the benthic Staurozoa. Haootia quadriformis thus potentially provides the earliest body fossil evidence for both metazoan musculature, and for Eumetazoa, in the geological record. – Alex Liu et al. Haootia quadriformis n. gen., n. sp., interpreted as muscular Cnidarian impression from the Late Ediacaran period (approx. 560 Ma). Proceedings of the Royal Society B, 2014 DOI: 10.1098/rspb.2014.1202
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