Coelacanths are deep-sea fish found off the coasts of southern Africa and Indonesia and can grow up to two metres in length. For a long time, scientists believed they were extinct.
In new research published in Nature Communications, we have discovered the best-preserved coelacanth fossil ever found from the ancient period millions of years ago, when these ancient marine creatures first evolved. The fossil comes from the Gogo Formation of Guniyandi Country in northern Western Australia.
We also studied the evolution of all the hundreds of coelacanth species known from the fossil record, to find out what drove the formation of new species at different eras.
The answer was surprising: the biggest influence on coelacanth evolution wasn’t the ocean.
Later, during the dinosaur age that began about 250 million years ago, coelacanths became more diverse. In total, we have found traces of more than 175 fossil species from around the world.
Finally, 66 million years ago, at the end of the Cretaceous period, all traces of coelacanths mysteriously vanished from the fossil record. For a long time, scientists assumed that coelacanths were victims of the massive asteroid impact that also spelled the death warrant for the dinosaurs (along with about three-quarters of all life on Earth).
Everything changed in 1938, when South African fishermen pulled a large, mysterious fish from the depths of the ocean that had never been seen before. Marjorie Courtenay-Latimer, a local museum employee with a keen interest in natural science, immediately recognized that the fish was special.
Courtenay-Latimer involved his friend JLB Smith, a renowned South African chemist with an interest in ichthyology (the study of fish). Smith identified and named the fish LatimeriaThe first living coelacanth known to science.
Discovering this “Lazarus fish” was like stumbling upon a live fish triceratops Dinosaurs still roam the forests of North America. Even today, coelacanths are often described as “living fossils.”
A new fossil coelacanth
Our team at Flinders University, together with other colleagues from Australia, Canada and Europe, discovered a new species of fossil coelacanth in Guniyandi Country, northern WA. Around 380 million years ago, the site was a tropical reef that harboured more than 50 species of fish.
Ngamugavi Wirngar ExplainedThe new fossil coelacanth is the first fish found in the region to have a name from the Guniyandi language, meaning “ancient fish” in honour of Wirngari, a respected elder of the community.
ngamugawi It is the best-preserved three-dimensional coelacanth from the Devonian period (359 million to 419 million years ago). This fossil provides great insight into the early anatomy of this genus.
Plate tectonics may have fueled the evolution of the coelacanth
Our study of the new species led us to analyse the evolutionary history of all known coelacanths. In doing so, we calculated rates of evolution over their 410 million-year history.
We found that coelacanth evolution has generally been gradual, with a few interesting exceptions.
In addition, we analysed a range of environmental factors that we considered to be potential candidates for influencing coelacanth growth rates. These included tectonic plate activity, ocean temperature, oxygen levels in the water and atmospheric carbon dioxide levels.
Of all the variables we looked at, tectonic plate activity had the greatest influence on the rate of coelacanth evolution. Because of habitat changes caused by seismic activity, new species of coelacanth were more likely to evolve as tectonic activity increased.
Are coelacanths still evolving?
In addition to analysing all the fossil coelacanths, we also took a closer look at two living species, Latimeria chalumnae And Latimeria menadoensis,
At first glance, these fish look almost identical to some of their counterparts from millions of years ago. However, upon closer analysis, we can see that they were actually quite different from their extinct relatives.
Whereas Latimeria It has stopped evolving new features, its body proportions and DNA details are still changing slightly. So it’s probably not a “living fossil.”
Alice Clement, Research Associate in the College of Science and Engineering at Flinders University and John Long, Strategic Professor in Palaeontology at Flinders University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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