Mystery critters

Cambrian muscle worm

Five hundred million years ago, in the Cambrian period, the oceans teemed with strange and unusual creatures that are now preserved as fossils. This period in Earth’s history is important because almost all known groups of animals appear very suddenly in the fossil record at this time. Many of them look just like their modern day counterparts, but several are much more weird and wonderful, with a very different appearance from anything alive today.

I was recently awarded the Whittington Award from the Palaeontological Association which includes a small research grant that will allow me to study one of these weird fossils. The creature in question is known as the “muscle worm”, or Myoscolex, and is particularly interesting because almost the whole fossil is made up of very well-preserved muscle fibres. It’s the oldest record of muscle tissue in the fossil record.

Me, taking a break from fossil hunting to cuddle an echidna
Me, taking a break from fossil hunting to cuddle an echidna

The material comes from the Emu Bay Shale fossil site, located on Kangaroo Island in South Australia. The original collection of fossils is nearly 35 years old now. These original fossils showed the muscle tissue of Myoscolex very clearly, but unfortunately we don’t know much about the rest of its body and scientists can’t even agree on what type of animal it is! Some people believe it is an annelid worm – a segmented creature – while others think it could be an early ancestor of either the arthropods, which includes animals like crabs, shrimp, spiders, centipedes, and insects, or the chordates, a group which includes any animal with a backbone, including ourselves.

Fortunately, many new fossils have been collected in the last few decades that will help us solve the mystery of the Cambrian muscle worm. Active collecting by the South Australian Museum and the University of New England has revealed hundreds of new specimens that show us more details about the anatomy of Myoscolex, including the head, legs, skeleton, and even its digestive system.

I have been working with researchers in Australia on Emu Bay Shale fossils for several years now, both on the fossil collections in the museum and in the field. The Whittington Award will allow me to travel to Australia to study the new muscle worm fossils. The research will involve taking photos, making drawings, and analyzing the nicest specimens under scanning electron microscopes. I will then come back to the Museum in Oxford and compare the fossil information with modern animals found in our collections here. All of this work should allow us to finally figure out what the Cambrian muscle worm really is.

Stay tuned as we try to solve this mystery….

Allison Daley – Museum Research Fellow


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