Evrim Yazgin
Cosmos science journalist
An exceptionally well-preserved skull from a fish which lived 384–382 million years ago helps explain how plate tectonics played a key role in the evolution of ancient bony fish which eventually led to humans.
The skull was found in a remote region of northern Western Australia. It lay in the Gogo Formation – a deposit which dates to the late Devonian period (419–359 million years ago). The Devonian is sometimes referred to as the “Age of Fishes”.
One group of fish which emerged during this time are coelacanths – lobe-finned fish which were thought to have gone extinct 66 million years ago at the end of the reign of dinosaurs.
More than 175 species of coelacanth have been identified from fossils going back to the earliest which lived 410 million years ago.
Coelacanths were found to be living off the coast of South Africa in 1938, earning the fish the title of “living fossil”.
These fishes – like the other living fossil, lobe-finned lungfish which can be found in Queensland – are closely related to the group of fishes that developed stronger limbs and climbed out of the water to lead to the evolution of all tetrapods including dinosaurs, whales and humans.
The newly discovered ancient species of coelacanth is described in a paper published in Nature Communications. It is named Ngamugawi wirngarri, meaning “ancient fish” in the local Gooniyandi/Guniyandi language of the Kimberley region where the Gogo Formation is located.
N. wirngarri’s skull is mostly complete and measures a little more than 2 cm in length.
“Our analyses found that tectonic plate activity had a profound influence on rates of coelacanth evolution,” says first author Alice Clement, an evolutionary biologist and palaeontologist from South Australia’s Flinders University. “Namely that new species of coelacanth were more likely to evolve during periods of heightened tectonic activity as new habitats were divided and created.”
The new finding confirms the Gogo Formation as one of the richest and best-preserved assemblages of fossil fishes and invertebrates in the world.
According to senior author John Long, also from Flinders University, the new fish “provides us with some great insight into the early anatomy of this lineage that eventually led to humans”.
“For more than 35 years, we have found several perfectly preserved 3D fish fossils from Gogo sites which have yielded many significant discoveries, including mineralised soft tissues and the origins of complex sexual reproduction in vertebrates,” says Long. “Our study of this new species led us to analyse the evolutionary history of all known coelacanths.”
The new fossil challenges the claim that coelacanth genus Latimeria should be considered living fossils.
“They first appear in the geological record more than 410 million years ago, with fragmentary fossils known from places like China and Australia,” says senior co-author Richard Cloutier from the University of Quebec in Rimouski. “However, most of the early forms remain poorly known, making Ngamugawi wirngarri the best-known Devonian coelacanth.”
“As we slowly fill in the gaps, we can start to understand how living coelacanth species of Latimeria, which commonly are considered to be ‘living fossils,’ actually are continuing to evolve and might not deserve such an enigmatic title,” Cloutier notes.
