Coelacanths are deep-water fish up to two metres long that were thought to be extinct.
Coelacanths are deep-sea fish that live off the coasts of southern Africa and Indonesia and can reach up to two metres in length. For a long time, scientists believed they were extinct.
In new research published in Nature Communications, we reveal the best-preserved coelacanth fossil yet found, from the ancient period hundreds of millions of years ago when these ancient sea dwellers first evolved. The fossil comes from the Gogo Formation in Gooniyandi Country in northern Western Australia.
We also study the evolution of the hundreds of coelacanth species we know from the fossil record to discover what drove the creation of new species over the eons.
The answer was a surprise: the biggest influence on coelacanth evolution was not the ocean.
Later, during the age of the dinosaurs, which began about 250 million years ago, coelacanths continued to diversify. In total, we have found traces of more than 175 fossil species from around the world.
Finally, at the end of the Cretaceous period, 66 million years ago, all signs of coelacanths mysteriously disappeared from the fossil record. For a long time, scientists assumed that coelacanths were victims of a massive asteroid impact that also signed the death knell for the dinosaurs (along with about three-quarters of all life on Earth).
That all changed in 1938, when fishermen in South Africa pulled from the depths of the ocean a large, enigmatic fish that was unlike anything they had ever seen before. Marjorie Courtenay-Latimer, a local museum employee with a keen interest in natural sciences, knew immediately that the fish was special.
Courtenay-Latimer recruited his friend J.L.B. Smith, a renowned South African chemist interested in ichthyology (the study of fish). Smith identified and named Lamentariathe first living coelacanth known to science.
Discovering this “Lazarus fish” was like stumbling upon a live fish. Triceratops A dinosaur that still roams the forests of North America today. Even today, coelacanths are often described as “living fossils.”
A new fossil coelacanth
Our team at Flinders University, along with colleagues from Australia, Canada and Europe, discovered a new species of fossil coelacanth in Gooniyandi Shire, northern Western Australia. Around 380 million years ago, the site was a tropical reef teeming with more than 50 species of fish.
Ngamugawi wirngarriThe new fossil coelacanth is the first fish found in the area to bear a name that came to us from the Gooniyandi language. The name means “ancient fish” in honour of Wirngarri, a respected elder of the community.
Ngamugawi It is the best preserved coelacanth in three dimensions from the Devonian period (between 359 and 419 million years ago). This fossil provides a great insight into the early anatomy of this lineage.
Plate tectonics drives coelacanth evolution
Our study of the new species led us to analyse the evolutionary history of all known coelacanths. To do so, we calculated the rates of evolution over their 410 million-year history.
We found that coelacanths have generally evolved slowly, with some intriguing exceptions.
In addition, we analyzed a number of environmental factors that we consider potential candidates for influencing coelacanth evolutionary rates, including plate tectonic activity, ocean temperatures, oxygen levels in the water, and atmospheric carbon dioxide levels.
Of all the variables we looked at, the one that had the greatest influence on the rate of coelacanth evolution was plate tectonic activity. New coelacanth species were more likely to evolve during periods of heightened tectonic activity, as seismic movement transformed habitats.
Are coelacanths still evolving?
In addition to our analysis of all fossil coelacanths, we also took a close look at the two living species, Latimeria chalumnae and Latimeria menadoensis.
At first glance, these fish look almost identical to some of their counterparts from hundreds of millions of years ago. However, upon closer inspection, we could see that they were, in fact, distinct from their extinct relatives.
While Lamentaria Essentially, it has stopped developing new features, its body proportions and the details of its DNA keep changing a bit. So maybe it's not a “living fossil” after all.
Alice Clement, Research Associate, Flinders University's Faculty of Science and Engineering, and John Long, Professor of Strategy in Palaeontology, Flinders University
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