June

Gogonasus andrewsae Long 1985, Paddys Valley, Kimberley Ranges, Western Australia

Museum Victoria, Melbourne, Australia

EMu user since 1997

KE client since 1983

june.jpgThis new fossil specimen at Museum Victoria may link fish and land animals, rewriting the history of animal evolution. Gogonasus (meaning "snout from Gogo") was a lobe-finned fish that lived 380 million years ago during the Late Devonian Period, on what was once a great barrier reef surrounding the north-west of Australia. Initially described from only a snout by John Long in 1985, this new specimen represents a complete fish and was found by a Museum Victoria expedition in July 2005 in a limestone nodule in the Kimberley Ranges known as the Gogo Formation.

Fish fossils preserved there were prepared using weak acetic acid which dissolves rock without harming the bone material. Four months of delicate preparation was required for the skull and pectoral fin to be revealed in perfect 3-D form. This specimen shows us that Gogonasus had large holes, called spiracles,  on top of the head which were used for taking in air. These structures would eventually evolve into the Eustachian tube or middle ear of higher land vertebrates. The front fin of Gogonasus shows remarkable similarity with that of all land vertebrates (tetrapods) in having a well-developed humerus, ulna and radius. This feature reveals that such fishes had much more in common with land animals than previously thought. The specimen was found by Tim Senden of the Australian National University (ANU), who has developed an ultra-fine CT scanner which was used to study the fossil at a level of detail never before seen. Research on the significance of the new fossil is a joint collaboration between Museum Victoria (John Long), the ANU (Gavin Young, Tim Senden) and Monash University students based at MV (Tim Holland, Erich Fitzgerald), and was published online in Nature magazine on October 18 2006.

Reproduced courtesy of Museum Victoria
Photographer: John Broomfield