Discover the world’s oldest fish, presumed extinct 60 million years ago, then rediscovered in a small fishing village

Before 1938, if you had asked a zoologist to name some of the oldest fish known to science, you would probably have heard of a strangely named lobe-finned fish known as a coelacanth. The name itself sounds ancient. Coelacanths first appeared in the early Devonian period, just over 400 million years ago.

What this zoologist wouldn’t have told you is that this ancient fish was still present in the ocean today. In fact, they probably would have laughed at the idea. Before the coelacanth was rediscovered in 1938, researchers thought the species had gone extinct at the end of the Cretaceous period, 65 to 70 million years ago.

The coelacanth is an example of a “Lazarus taxon,” an animal that appears to disappear from the fossil record only to be rediscovered in its same form millions of years later. This can happen for several reasons. Most commonly, it highlights the sporadic and incomplete nature of the fossil record, especially when the number of individuals of a given taxon is small.

In the case of the coelacanth, the zoological community was shocked in 1938 when a 32-year-old museum worker, Marjorie Courtenay-Latimer, working in the small South African town of East London, was presented with a fish that could not be identified. It had been caught by a local fisherman while fishing just off the mouth of the Chalumna River in South Africa’s Eastern Cape province.

Courtenay-Latimer couldn’t identify the fish either, so she had it stuffed and sought the advice of an expert – Professor James Leonard Brierley Smith, a university professor and marine life expert. When Brierley Smith received Latimer’s sketch and notes on the unidentified fish by mail, he responded by telegram with a now-famous message: “MOST IMPORTANTLY, PRESERVE SKELETON AND GILLS = FISH DESCRIBED.”

When Brierley Smith arrived in East London, he confirmed his hunch: the fish was indeed an ancient coelacanth. The discovery sent shockwaves through the zoological community, and earned Brierley Smith and Courtenay-Latimer international recognition.

Interestingly, a second specimen was not discovered until 15 years later. The second coelacanth was found in 1952 by two fishermen from the Comoros Islands, a small chain of islands nestled between Madagascar and the African mainland.

In the 1990s, scientists made another remarkable discovery, discovering a second species of coelacanth in the Indonesian islands. Thus, at present, coelacanths are divided into two species: the Western Indian Ocean coelacanth (Latimeria chalumnae), mainly found near the Comoros Islands, off the east coast of Africa, and the Indonesian coelacanth (Latimeria menadoensis).

Here are some of the reasons why the ancient coelacanth has been able to stand the test of time.

• AdaptationsCoelacanths have a number of unique physiological features that have served them well for millions of years. For example, their lobed pectoral fins, thought to be the precursors to the limbs of terrestrial vertebrates, are well adapted for maneuvering in deep, complex underwater environments.
• Stable environmentCoelacanths live in stable, deep environments, such as underwater caves and seafloors, that have not changed much over geological time. These environments are less exposed to predators and competition, allowing coelacanths to avoid drastic evolutionary pressures.
• Low metabolismCoelacanths have a relatively slow metabolism, which allows them to survive in environments where food may be scarce. Their slow metabolism contributes to their ability to withstand long periods of environmental change.
• Specialized nicheTheir ecological niche, typically located in deep, cold waters, has not changed much. This stability of their habitat means that they have been under less pressure to adapt than species living in more variable environments.

Overall, the coelacanth’s combination of evolutionary adaptations, environmental stability, and specialized ecological niche has allowed it to survive significant changes in Earth’s history.

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