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The oldest mother

John Long1,2, Kate Trinajstic3, Gavin Young1, & Tim Senden4

1 Research School of Earth Sciences, The Australian National University, Canberra, ACT;
 2 Museum Victoria, Melbourne, Victoria;
3 School of Earth & Geographical Sciences, The University of Western Australia, Perth, WA;
4 Dept. Applied Maths, Research School of Physical Sciences & Engineering, The Australian National University, Canberra, ACT.

Figure 1. The oldest known vertebrate mother, Materpiscis, in the act of live birth - an artistic reconstruction by RSES Ph.D student Brian Choo .

 

A well-preserved embryo was discovered inside a 380-million-year old fossil fish collected from Gogo (Kimberley region, WA), during a 2005research trip under an Australian Research Council Discovery Project based at ANU (DP0558499; Chief Investigators Gavin Young and John Long). This has proved to be the oldest example of live birth known amongst the vertebrates (animals with backbones).  The discovery was published in Nature in May, 2008, and received wide media coverage. The new genus and species of placoderm (armoured) fish was named Materpiscis attenboroughi in honour of Sir David Attenborough, who first brought the world-famous Gogo fossil fish deposit to public attention in the 1979 TV series 'Life on Earth'.

The Gogo fossil fish are preserved in limestone nodules, and can be extracted using acetic acid. This specimen was prepared at Museum Victoria by Dr John Long, Head of Science at the museum, who is also an ANU Adjunct Professor at RSES.  During the acid preparation he discovered a partly developed small skeleton inside the body cavity of the larger fish. The specimen was brought to Canberra to be scanned by Dr Tim Senden (ANU Department of Applied Mathematics) using the 3D XCT scanner built and housed in the Research School of Physical Sciences & Engineering. This revealed unique preservation of an umbilical cord and recrystallised yolk sac, soft tissue structures very rarely observed in fossils, let alone specimens as old as the Gogo deposit.  

Major collections of Gogo fossil fish are held in the Natural History Museum, London, the WA Museum, Perth, and at the ANU in Canberra. The ANU collection includes the actual specimens used by the BBC for the 'Life on Earth' TV production in 1979. Gogo is recognised internationally as producing the world's best preserved Devonian fossil fish, complete articulated skeletons that look like modern specimens. Recent research by John Long and Dr Kate Trinajstic (University of Western Australia) has shown that phosphatiised muscle and nerve fibres were also preserved in some specimens (published 2007). In early 2008 Kate re-examined some placoderm specimens in the WA Museum collection and found three small skeletons inside another fish (Austroptyctodus) that is closely related to Materpiscis. The tiny embryos had been previously overlooked. Earlier research by Dr Gavin Young (RSES) had demonstrated copulatory organs in male Austroptyctodus  specimens, showing that these placoderms had a very advanced reproductive biology involving internal fertilisation, as in modern sharks. The preserved embryos now demonstrate that these placoderms did not lay eggs, but produced live young, a remarkably advanced reproductive strategy to have developed so early in the evolutionary history of backboned animals.

Another field trip to Gogo in 2008 has yielded a range of new specimens, including some fish groups not previously found at Gogo. These are currently being prepared and researched in Melbourne by Dr Long and RSES Ph.D student Brian Choo. John Long received the Australasian Science Prize for 2008 in recognition of this research, which was also featured as a Case Study on p. 60 of the Australian Research Council Annual Report for 2007-2008.



Long, J.A., Trinajstic, K., Young, G.C. & Senden, T. 2008. Live birth in the Devonian Period. Nature 453: 650-652.

Trinajstic, K., Marshall, C., Long, J. & Bifield, K. 2007. Exceptional preservation of nerve and muscle tissues in Late Devonian placoderm fish and their evolutionary implications. Biology Letters 3: 197-200 (doi:10.1098/rsbl.2006.0604)