Coelacanths, ancient deep-sea fish that were once believed to be extinct, have long fascinated scientists. In a groundbreaking study recently published in Nature Communications, researchers have unveiled the best-preserved coelacanth fossil ever found, offering valuable insights into the evolution of these enigmatic creatures.

The fossil, discovered in the Gogo Formation on Gooniyandi Country in northern Western Australia, comes from the Devonian Period, hundreds of millions of years ago when coelacanths first appeared. This extraordinary find allows scientists to gain a deeper understanding of what the earliest coelacanths looked like.

The study also delved into the evolution of the hundreds of coelacanth species known from the fossil record. Researchers aimed to uncover the driving factors behind the creation of new species over time. Surprisingly, the study revealed that tectonic activity played a significant role in coelacanth evolution. When Earth's vast crust plates were in greater motion, new coelacanth species were more likely to emerge.

Coelacanths are unique "lobe-finned" fish, with robust bones in their fins similar to the structure of human arms. Scientists believe that they are more closely related to tetrapods, which are animals with backbones and four limbs, than to most other fish species.

With fossils dating back over 410 million years, coelacanths have witnessed significant changes throughout Earth's history. During the age of dinosaurs, roughly 250 million years ago, these fish diversified, leaving behind traces of more than 175 fossil species found worldwide.

However, approximately 66 million years ago, at the end of the Cretaceous period, all evidence of coelacanths suddenly vanished from the fossil record. Scientists initially attributed this disappearance to the massive asteroid impact that caused the extinction of dinosaurs and numerous other species.

Everything changed in 1938 when a momentous discovery in South Africa rewrote the coelacanth narrative. Local fishers pulled a mysterious fish from the depths of the ocean, catching the attention of Marjorie Courtenay-Latimer, an avid naturalist working at a local museum. She immediately recognized the fish's significance and enlisted the help of J. L. B. Smith, a renowned South African chemist and fish expert. Together, they identified and named the Latimeria, the first living coelacanth known to science.

This extraordinary find was comparable to stumbling upon a living Triceratops in modern times. Coelacanths were subsequently dubbed "living fossils" due to their remarkable resemblance to their ancient ancestors.

Now, a team of researchers from Flinders University, along with colleagues from Australia, Canada, and Europe, have discovered a new fossil coelacanth species on Gooniyandi Country in northern Western Australia. Inhabiting a tropical reef around 380 million years ago, this site was teeming with more than 50 species of fish.

The newly discovered species, named Ngamugawi wirngarri, is the best-preserved coelacanth from the Devonian Period. This fossil provides invaluable insight into the early anatomy and lineage of these ancient fish.

Furthermore, the study's analysis of all known coelacanths, both fossils and living species, revealed fascinating patterns of evolution. Coelacanths generally evolved slowly over their 410 million years of existence, with a few notable exceptions. Interestingly, the study identified tectonic plate activity as the greatest influencing factor on the rate of coelacanth evolution. With enhanced seismic movement transforming habitats, new coelacanth species were more likely to evolve.

While the two living coelacanth species, Latimeria chalumnae and Latimeria menadoensis, may appear strikingly similar to their extinct counterparts, closer analysis demonstrates distinct differences. Although the species has ceased to evolve new features, subtle changes in body proportions and DNA suggest that coelacanths are still undergoing some evolutionary processes.

The discovery of a well-preserved fossil and the subsequent analysis of coelacanth evolution offer a remarkable glimpse into the past and present of these extraordinary fish. With further research, scientists hope to unravel more mysteries surrounding the ancient lineage of coelacanths and their continued existence in our modern world.

Reference:
"A Late Devonian coelacanth reconfigures actinistian phylogeny, disparity, and evolutionary dynamics." Nature Communications (2024). DOI: 10.1038/s41467-024-51238-4. www.nature.com/articles/s41467-024-51238-4.