29 October 2013
Researchers from the South Australian Museum have returned from their biannual field trip to fossil hotbeds on Kangaroo Island, with a swathe of new species to describe.
Since fossilised animals from the early Cambrian period (half a billion years ago) were discovered at a new quarry in 2007, Museum scientists have been visiting, collecting and analysing specimens from a very special site.
Palaeontology is the study of ancient life from fossils of organisms. Researchers’ work on Kangaroo Island has focused on fossils of the Emu Bay Shale Biota that preserve the intricate details of early animals, even the ones without hard skeletons.
Scientists collected lots of new fossils, many of them being ancient marine arthropods (animals with an exoskeleton and jointed legs, represented by living insects, arachnids and crustaceans), which they will study and describe here at the Museum on North Terrace.
Leading Palaeontologist Dr Jim Gehling said, “That’s the hook that keeps you going back – the chance of finding more and better specimens or a rare part. On this trip we found some appendages of this beast, Anomalocaris, an early Cambrian predator.”
Museum Senior Researcher in Palaeontology Dr Mike Lee added, “The purpose of the October visit was to continue excavation at this incredibly exciting field site at Kangaroo Island and find more weird critters! But we were targeting a few very important animals, including an animal which could be an early relative of vertebrates – animals with backbones, including ourselves.”
Because some creatures can be delicate and their full body not preserved in detail, scientists have to persevere to find better specimens on each visit, fitting the pieces of the puzzle together and producing more accurate illustrations of the ancient life.
“One of the things we’ve discovered at Emu Bay is that even though we’ve dug down a couple of metres, we still aren’t in fresh rock,” said Dr Gehling.
“It’s really only when you get to that fresh material – which is not easy – that you might get a whole different kind of preservation. In other words, rocks tend to crumble away in your fingers near the surface due to salt and weather decay. Below that, you might get quite different things preserved. I would argue that we get to see roughly one per cent of the fossils in every sample you pick up with your hand, because it depends where your hammer hits.
“We’d like to find bigger and more finely preserved samples, and we’re learning which levels to concentrate on to get them. If you could follow those layers deeper into the ground where they are fresher, you might even get more material. So that’s really quite exciting, to narrow it down to a few horizons. If you want something rare, the eyes of the Anomalocaris for instance, those are the layers you’ve got to go for.”
Dr Gehling says the eye fossils – which have been the subject of two Nature papers by South Australian Museum scientists and colleagues – cannot be found anywhere else in the world.
Dr Lee says the initial ‘explosion’ in fossil discovery is starting to slow down slightly. “The discovery curve is starting to level off a little bit in the sense that we are finding fewer new things, but we are still finding new things on every trip. On this trip the team found some new arthropods, which they will spend time describing and identifying,” said Dr Lee. He also led an international delegation of 40 scientists (from the 14th biennial Conference on Australasian Vertebrate Evolution, Palaeontology and Systematics or CAVEPS) around the Kangaroo Island site, to explain to them the importance and uniquenss of this exciting fossil deposit.
Kangaroo Island offers research subject matter for many different scientists. University of Adelaide researcher and South Australian Museum Honorary Dr Diego Garcia-Bellido says usually a number of specimens need to be collected over the years in order to be able to understand, and show people, what a creature actually looked like.
“The fossils show not only the skeleton, but also the skin or cuticle, the organs with the last meal, sometimes even the muscle strands! These would have been animals living in maybe 50 or 100 metres of water, so not especially deep... and they are very common. We might find 1000 specimens in less than a square metre,” he said.
“We’re a lot more cautious about how much we bring back to the Museum because you need space to hold them and time to invest in cataloguing them. Now we might bring back 100-150 specimens over 10 days, twice a year, and with that we can bring the stuff we’re going to use for descriptions. However, sometimes we bring back things we already know a lot about, like trilobites, because if they’re really well preserved, we can use them for teaching purposes or exhibition.
By visiting Kangaroo Island and collecting important specimens, the scientists can tell us more about the earliest forms of animal life, what they looked like, how they moved, what and how they hunted, and how they evolved and are related to each other.
The fossil expeditions have involved an important and dedicated team of more than a dozen people; the Museum is particularly grateful to Dr John Paterson (University of New England) and Associate Professor Jim Jago (University of South Australia), Mary-Anne Binnie (Collection Manager, Palaeontology), as well as long-term volunteers Mike Gemmell, Ronda Atkinson, Katrina Kenny and Natalie Schroeder (PhD student) in collecting, analysing, illustrating and communicating the stories of the Kangaroo Island fossils. They are also most grateful to the landowners for their continued support and enthusiasm.