NEWS - An ancient Devonian coelacanth has been remarkably well preserved in a remote location in Western Australia linked to increased tectonic activity. An international team of researchers analysed fossils of the primitive fish from the Gogo Formation of Ngamugawi wirngarri, which straddles a key transition period in the history of coelacanths, between the most primitive and more modern forms.
The new fish species adds to the evidence for Earth’s evolutionary journey. Climate change, asteroid strikes and plate tectonics are all key subjects in the origins and extinctions of animals that played a major role in evolution. Is the world’s oldest ‘living fossil’ the coelacanth still evolving?
“We found that plate tectonic activity had a major influence on the rate of coelacanth evolution. New species are more likely to have evolved during periods of increased tectonic activity when new habitats were divided and created,” says Alice Clement of Flinders University in Adelaide.
The Late Devonian Gogo Formation contains a particularly well-preserved collection of fish and invertebrate fossils. Fossils from the Devonian Period (359-419 million years ago) provide important insights into the early anatomy of this lineage and the evolution that led to humans.
“Over 35 years, we have recovered some of the most beautifully preserved 3D fossils from the Gogo site and have made many important discoveries, including mineralised soft tissue and the origins of complex sexual reproduction in vertebrates,” said John Long from Flinders University.
Much of human anatomy dates back to the Early Palaeozoic (540-350 million years ago). Jaws, teeth, a ossified skull, genitals, a chambered heart and paired lungs appeared in early fish. The Gogo Formation is an ancient tropical reef that was home to more than 50 species of fish 380 million years ago, now covered by dry rock.
“We calculated the rate of evolution over 410 million years. The evolution of coelacanths has slowed dramatically since the time of the dinosaurs, with some interesting exceptions,” Long said.
Coelacanths are deep-sea fish that live off the coast of East Africa and Indonesia and can grow up to 2 metres (6.6 feet) long. These lobe-finned fish have strong bones in their fins that are similar to the bones in a human arm. They are thought to be more closely related to lungfish and tetrapods than to most other fish.
Over the past 410 million years, there are more than 175 species of coelacanths worldwide. During the Mesozoic Era, the age of the dinosaurs, coelacanths diversified significantly, with some species developing unusual body shapes. However, by the end of the Cretaceous Period (66 million years ago) they mysteriously disappeared from the fossil record.
The end-Cretaceous extinction event, triggered by a large asteroid impact, wiped out 75% of all life on Earth, including all non-avian dinosaurs. Coelacanths were also wiped out as victims of the same mass extinction event.
But in 1938, fishermen off the coast of South Africa unearthed a mysterious giant fish from the depths of the ocean, and it has since gained cult status in the world of evolutionary biology. New research challenges the idea that living coelacanths are the oldest living fossils.
“Coelacanths first appear in the geological record more than 410 million years ago, with isolated fossils from places like China and Australia. However, most early forms are poorly known. Ngamugawi wirngarri fills that gap,” says Richard Cloutier of the Université du Québec à Rimouski.
Original research
Clement, A.M., Cloutier, R., Lee, M.S.Y. et al. A Late Devonian coelacanth reconfigures actinistian phylogeny, disparity, and evolutionary dynamics. Nature Communications 15, 7529 (2024), DOI:10.1038/s41467-024-51238-4