Coelacanths: Fossil Fish - An Ancient Swimmer
Coelacanth is the common name for an order of fish that includes the oldest living lineage of Sarcopterygii (lobe-finned fish + tetrapods) known to date. Until its recent discovery it was believed that the Coelecanth became extinct 65 million years ago.
The coelacanth was thought to have gone extinct with the dinosaurs. Rediscovered in 1938, it is chronicled here in a rare photographic account.
It's not every day that a living fossil shows up in a fisherman's net.
But that's what happened in 1938, when a South African museum curator named Marjorie Courtenay-Latimer spied a bizarre creature with thick scales, unusual fins, and an extra lobe on its tail, amid an otherwise ordinary haul of fish. Though she didn't know it straightaway, Courtenay-Latimer had rediscovered the coelacanth, which was assumed to have died out at the end of the Cretaceous period but somehow outlasted many of its prehistoric peers, dwelling deep in the ocean, undisturbed—and undetected—for eons.
Since this chance sighting, Latimeria chalumnae have been found in several pockets in the Indian Ocean. No one knows how many there are—maybe as few as 1,000 or as many as 10,000. Because of the depth of their habitat, they have mainly been photographed by submersibles and remotely operated vehicles. Divers first documented the fish in 2000; in January and February 2010, a specially trained team dived deep to take pictures of a small colony in Sodwana Bay, South Africa.
During 95 hours of diving, the photographer and his team spent a total of 81 minutes swimming alongside four coelacanths. The fish are easily distinguished by distinctive white markings.
The expedition team made 21 dives to depths of 300 to 400 feet in South Africa's Sodwana Bay area. Over the course of four weeks, they spotted coelacanths only six times. The nocturnal animals hide in underwater caves by day, then venture out at night, feeding on small fish, squid, and octopus.
A crystal layer behind the coelacanth's retina reflects light like a mirror, a boon in the ocean's dim waters.
Its sail-like first dorsal fin provides stability while swimming. An extra tail lobe, unique to coelacanths, can be seen today and in fossils from millions of years ago.
Named by a 19th-century naturalist, "coelacanth" comes from the Greek for "hollow spine"—a reference to the hollow spines that are part of its fin structure.
The coelacanth's slow, graceful stroke is like no other fish's. It moves left pectoral and right pelvic fins, then right pectoral and left pelvic fins—akin to the cross-step of tetrapods. When the expedition team visited in early 2010, the coelacanths ignored the humans, says photographer Ballesta, except the one above: "This is the moment he tried to smile to me."
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