Fossil discovery reveals earliest evidence of animals with muscles
A fossil discovered in Newfoundland and Labrador may contain one of the first animals on earth and, quite possibly, the oldest evidence of muscle tissue ever recorded.
Dr. Alex Liu holds a PhD from the Department of Earth Sciences at Oxford University, and was lead author on a paper published in August in the journal Proceedings of the Royal Society B. He discovered the fossil just over five years ago on the Bonavista Peninsula.
Professor Duncan McIlroy of the Department of Earth Sciences at Memorial University, co-supervised Dr. Liu with Professor Martin Brasier, an adjunct professor at Memorial who is based out of the University of Oxford. They also co-authored the paper along with two other co-supervised graduate students.
“These rocks have been known about since the mid-60s. But there are still things lots of things to be discovered if you know what you are looking for,” said Professor McIlroy. “During his time at Memorial as a visiting student, Alex found some fossil trails at Mistaken Point. That implied the presence of animals that could move, which in turn implies the presence of muscles since you need at least some degree of muscular control in order to move. The question, then, became what actually made those trails?”
Professor McIlroy says their first thought was that the trails were made sea anemones, fairly simple organisms that they found could produce similar trails in the lab. But they had no direct proof. Then this new discovery was made.
“The preservation of this fossil shows very fine details and looks like nothing I’ve ever seen before, and there are many fossils preserved in the rocks at Mistaken Point and elsewhere in the region. It simply resembles none of the known Ediacaran fossils, most of which have a fractal-like organization of frond-like elements.”
The new fossil, named Haootia quadriformis, is made up of bundles of fibres in a four-fold symmetrical arrangement, and is similar to modern animals from the cnidarian group (which includes corals, sea anemones and jellyfish). The Memorial and Oxford researchers debated the findings and eventually agreed it was an early stauromedusan cnidarian, and that the bundles represent muscle tissue. Stuaromedusans look a little like upside-down jellyfish on a stalk.
“Cnidarians are actually quite low down on the evolutionary tree and are some of the simplest animals that we have, so it's not completely out of the realm of possibility that stauromedusans would be among the earliest muscular organisms,” said Prof. McIlroy.
The finding is such an important one because historically it was thought that the origin, evolution and spread of animals began during the Cambrian period, 541 million years ago. But these fossils date back to the earlier Ediacaran period, which was approximately 560 million years ago.
“The first person to tackle this was Darwin. He noticed that right before Cambrian period, you have rocks with essential no fossils in them, and then suddenly there are rocks teeming with all kinds of animals; by the end of the Cambrian basically all the modern groups had evolved,” said Prof. McIlroy. “People call that the “Cambrian Explosion.” The question has always been, did animals all of a sudden evolve, and then rapidly diversify into a plethora of different groups, or were there animals further back but they were missing from the fossil record?”
Prof. McIlroy’s group has previously documented the earliest fossil trails at Mistaken Point has demonstrated to many that animals did indeed originate much further back than previously believed, and this new fossil also seems to confirm that theory.
Funding for this research was provided by the Natural Environment Research Council, The Natural Sciences and Engineering Research Council of Canada, the Burdett Coutts Fund of the University of Oxford, the National Geographic Global Exploration Fund, and a Canada Research Chair to Prof. McIlroy.