Origin of the species might need rethink

Dr Gavin Young and fellow ANU researches have discovered a new species of ancient fish they have named "Edenopteron Keithcrooki". Dr Young is pictured with a life size model of the fish built by Baz Crook, son of Professor Keith Crook, who the fish is named after. Photo: Melissa Adams

By Fleta Page

Reporter at The Canberra Times

After five years of painstaking work, researchers from the Australian National University have identified a new species of fish, which raises questions about current theories of the evolution of land animals.

The four researchers suspected they were onto something big when in 2008 they found a four-centimetre-long fang while searching for remains of a toothless armoured fish in rocks near Eden.

But it took years and ''thousands of man hours'' to put all the pieces together, catalogue them and determine that the 360-million-year-old remains were of a large, previously unknown species of predatory lobe-finned fish.

''It's good fun to find these things and dig them up … [but] you bring it back and then you're confronted by this great mass of blocks and what does it all mean?'' Dr Gavin Young of ANU's school of earth sciences said.

''We could see all the bone, but we couldn't work out what it was - we thought we had two fish, two skulls jumbled up together. Later on we discovered it was just one skull which had been slightly displaced.''

Dr Young, his son Ben Young, Robert Dunstone and Dr Timothy Senden called the species Edenopteron keithcrooki, which became the official name on Thursday with the publication of their peer-reviewed findings in the international journal PLOS ONE.

It's named in honour of its Eden origins and Professor Keith Crook of the former ANU geology department, who now lives there and pioneered geological work in the region.

It's believed descendants of Devonian-period lobe-finned fish, such as the Edenopteron, evolved into the first land animals, but Dr Young said hypotheses of where this happened may need to be re-evaluated with the discovery of the Edenopteron.

''Edenopteron was put in a family named after another fish found in Canowindra [in NSW],'' he said. ''When the Canowindra fish were described about 15 years ago, they were thought to be related to fish from the northern hemisphere and there's sort of a complete idea about how the land animals evolved from this entire group, and it all happened in the northern hemisphere.

''Now that we've got the Eden fish and two fish from Canowindra, they actually form their own group, it really means that the entire sort of framework for how the first land animals actually evolved has to be completely rethought.''

While only the head and pectoral girdle of the Edenopteron has been excavated and reconstructed, Dr Young and his team believe the fish - which has a 48-centimetre-long jaw - would likely have been about three metres in length.

''It's a pretty big fish, it would have been a pretty fearsome predator, sort of on the scale of a saltwater crocodile today.

''We know that part of the pectoral girdle is still in the rock, so if we can lift up a few more blocks, we might find that the body is actually preserved in the rock.''

The team applied for a permit to continue their excavation in Ben Boyd National Park six months ago, but are still waiting to hear back.