The Ginkgo tree, the nautilus (a type of mollusk), and the coelacanth are not biologically related, but part of their evolutionary history shares an astonishing similarity: these organisms are referred to as “living fossils.” In other words, they seem to have escaped the transformations that typically occur over time through the process of evolution.
For the past 85 years, the coelacanth has been dubbed a “living fossil” because it evokes the age of dinosaurs. These fish belong to the group of lobe-finned fish, which also includes lungfish (fish with lungs) and tetrapods.
Few vertebrate species evoke as much curiosity as the coelacanth, due to the fascinating story of its discovery as well as its “living fossil” status. Moreover, only two species of coelacanth have survived this long evolutionary process, and they are currently threatened with extinction.
Ngamugawi wirngarri coelacanth in its Devonian coral reef habitat. (Photo: Katrina Kenny)
A Major Discovery in Western Australia
Utilizing the latest technological advances and innovative analytical methods, scientists are striving to gain a better understanding of the evolutionary processes of these fascinating species, often referred to as “living fossils”, and the 410 million-year evolutionary history of coelacanths.
This research, recently published in the journal Nature Communications, identified and described the fossil of an extinct coelacanth species that is 380 million years old and was discovered in Western Australia.
The remarkably well-preserved fossils date back to a crucial transitional period in the long evolutionary history of this fish. This research is the result of international collaboration among researchers affiliated with organizations in Canada, Australia, Germany, the United Kingdom, and Thailand.
Charles Darwin was the first to use the term “living fossil” in his book On the Origin of Species in 1859 to refer to living species that he considered “anomalous” compared to other species at that time. Although this concept was not clearly defined in Darwin’s era, it has been adopted by hundreds of biologists since then. However, the term “living fossil” remains a topic of debate within the scientific community.
More than 175 species of coelacanths existed between the Late Devonian (419 to 411 million years ago) and the end of the Cretaceous period (66 million years ago). In 1844, Swiss paleontologist Louis Agassiz identified a specific group of fossil fish, which he named the coelacanth order.
For nearly a century, it was believed that coelacanths went extinct at the end of the Cretaceous period, around 66 million years ago. During this time, nearly 75 percent of life on Earth became extinct, including most dinosaurs.
Then, on December 22, 1938, Marjorie Courtenay-Latimer, curator of the East London Museum in South Africa, received a call from a fisherman who had caught a rare and unusual fish. She recognized it as an unknown species and contacted South African ichthyologist JLB Smith, who confirmed that this was indeed the first living coelacanth ever observed.
In 1939, Smith named this species Latimeria chalumnae, commonly referred to as gombessa. Since then, this species, found along the eastern coast of Africa near the Comoros Islands, in the Mozambique Channel, and offshore South Africa, has attracted considerable scientific interest.
In 1998, a second living coelacanth species, Latimeria menadoensis (known as ikan raja laut, the king fish of the sea, in Indonesian), was discovered off the coast of Sulawesi, Indonesia. These two species are the only survivors of an ancient lineage that appears to have evolved very little over the past few million years.
After the discovery of Latimeria chalumnae, coelacanths were considered vertebrates whose body shape changed little over time, indicating a slow evolutionary process.
To date, more than 50 species of fossil fish have been identified at Gogo. This diverse group of fish, along with various marine invertebrates, coexisted in warm marine coral reefs during the Devonian period approximately 380 million years ago.
The latest research indicates that coelacanths evolved rapidly early in their history during the Devonian period, but this evolutionary process slowed down afterward. Evolutionary innovations nearly ceased after the Cretaceous period, suggesting that for some characteristics, coelacanths, like Latimeria, appear to have been frozen in time. The slow evolution of coelacanths suggests that they are not “living fossils,” but rather the result of a complex evolutionary process.
