Coelacanth
Coelacanths are an ancient group of lobe-finned fish in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods than to ray-finned fish.
- Scientific classification
- Class Actinistia, order Coelacanthiformes
- Extant genus
- Latimeria (two species)
- Known for
- Living fossil; Lazarus taxon
- Distribution
- Southern/eastern Africa and northern Indonesia
Lore & Background
Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local fisherman. She contacted ichthyologist J. L. B. Smith, who confirmed its importance.
Reader's Guide
Coelacanths are significant as a Lazarus taxon—an evolutionary line that seemed to disappear from the fossil record only to reappear much later. Their discovery over 60 million years after their supposed extinction reshaped understanding of vertebrate evolution. As lobe-finned fish more closely related to tetrapods than to ray-finned fish, they were considered a transitional form between fish and tetrapods. The extant genus Latimeria is often called a 'living fossil' because it was considered the sole remaining member of a taxon otherwise known only from fossils, evolving a bodyplan similar to its current form approximately 400 million years ago. However, studies of fossil coelacanths have shown that their body shapes and niches were much more diverse than previously thought, and often differed significantly from Latimeria. Coelacanths retain an oil-filled notochord and, in living species, a small vestigial lung, while fossil coelacanths had a lung surrounded by heavily calcified casing, likely functional for air breathing.
Did You Know?
- Coelacanths are more closely related to lungfish and tetrapods than to ray-finned fish.
- The genus name Latimeria commemorates Marjorie Courtenay-Latimer, who discovered the first specimen.
- Coelacanths have an oil-filled notochord instead of a vertebral column.
Frequently Asked Questions
What is a coelacanth?
Coelacanths are lobe-finned fish placed in the class Actinistia and the order Coelacanthiformes. They belong to the sarcopterygian lineage, which ties them more closely to lungfish and four-limbed vertebrates than to the ray-finned fish that dominate today's oceans.
Why is the coelacanth called a living fossil?
The label (more precisely, a Lazarus taxon) comes from the fact that the group was assumed extinct for roughly 66 million years before a living individual was hauled up in a trawl net off South Africa in 1938. Their overall body shape has stayed strikingly consistent across hundreds of millions of years of fossil evidence.
How is a coelacanth related to other fish and animals?
As a sarcopterygian, the coelacanth sits on the same evolutionary branch as lungfish and tetrapods, making it a closer relative of four-limbed land animals than of the ray-finned fish that make up the overwhelming majority of modern species. In practical terms, a coelacanth shares more deep ancestry with a human than it does with a salmon.
Where can you find coelacanths in the wild today?
The two surviving species are restricted to deep, steep-sloped waters off the southern and eastern coasts of Africa and off the northern coasts of Indonesia. Both are pelagic deep-sea dwellers, typically encountered well below the photic zone along submarine cliffs.
How many species of coelacanth exist?
Only two living species are recognized, both in the genus Latimeria: the West Indian Ocean coelacanth (L. chalumnae) and the East Indonesian coelacanth (L. menadoensis). No other extant representatives of the class Actinistia are known.
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