Paleontologists Dr Martin Brasier of the University of Oxford and the Memorial University of Newfoundland, Dr Alexander Liu of the University of Cambridge and their colleagues have uncovered the fossil of a muscle-bearing organism that thrived in what is now Newfoundland in Canada during the Ediacaran period, about 560 million years ago.
Artistic reconstruction of Haootia quadriformis. Scale bar – 10 mm. Image credit: Martin Brasier.
According to the scientists, the newly-discovered fossil, named Haootia quadriformis, provides the oldest evidence of muscle tissue – the bundles of cells that make movement in animals possible.
They have interpreted it as a cnidarian, the group which contains modern animals such as corals, sea anemones and jellyfish.
It differs from any previously described Ediacaran fossil (635 to 541 million years ago), as it comprises of bundles of fibers in a broadly four-fold symmetrical arrangement: a body plan that is similar to that seen in modern cnidarians.
“The evolution of muscular animals, in possession of muscle tissues that enabled them to precisely control their movements, paved the way for the exploration of a vast range of feeding strategies, environments, and ecological niches, allowing animals to become the dominant force in global ecosystems,” explained Dr Liu, who is the first author of a paper describing Haootia quadriformis in the journal Proceedings of the Royal Society B.
Haootia quadriformis, holotype specimen. Scale bar – 10 mm. Image credit: Alexander G. Liu et al.
Historically, the origin, evolution and spread of animals has been viewed as having begun during the Cambrian Explosion, a period of rapid evolutionary development starting 541 million years ago when most major animal groups first appear in the fossil record.
Dr Liu said: “however, in recent decades, discoveries of preserved trackways and chemical evidence in older rocks, as well as molecular comparisons, have indirectly suggested that animals may have a much earlier origin than previously thought.”
“The problem is that although animals are now widely expected to have been present before the Cambrian Explosion, very few of the fossils found in older rocks possess features that can be used to convincingly identify them as animals.”
“Instead, we study aspects of their ecology, feeding or reproduction, in order to understand what they might have been.”
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Alexander G. Liu et al. 2014. Haootia quadriformis n. gen., n. sp., interpreted as a muscular cnidarian impression from the Late Ediacaran period (approx. 560 Ma). Proc. R. Soc. B, vol. 281, no. 1793; doi: 10.1098/rspb.2014.1202
