Buzz
The ocean is home to countless species, yet none are as astonishing as the coelacanths. These ancient fish, once believed extinct, have baffled scientists and revolutionized our understanding of evolutionary biology.
1. COELACANTHS HAVE EXISTED FOR OVER 407 MILLION YEARS.
The Devonian period, spanning 416 to 358 million years ago, was a time of significant change. Ferns emerged, trilobites thrived in the seas, vertebrates ventured onto land, and fish diversified, earning the era its title, "the age of fish." During this period, the earliest-known coelacanth appeared in what is now Australia, dating back 407 to 409 million years. Like their modern counterparts, these ancient fish were part of the sarcopterygians, or "fleshy-limbed vertebrates," characterized by their bony structures and limb-like fins. These fins hint at a shared ancestry with terrestrial vertebrates, which later evolved into amphibians, reptiles, and mammals. In fact, humans are not just descendants of sarcopterygians—we are, biologically, sarcopterygians.
2. THE TERM COELACANTH TRANSLATES TO “HOLLOW SPINE.”
This name refers to the hollow, tube-shaped rays found in their dorsal fins. The word coelacanth originates from Coelacanthus granulatus, a species named by zoologist Louis Agassiz in the 1830s. Interestingly, Coelacanthus granulatus was the first coelacanth ever documented scientifically. Since its discovery, more than 120 other species have been identified, including those still living today. (We’ll delve into them shortly.)
3. THEY EXISTED IN A WIDE VARIETY OF FORMS AND SIZES.
Following the Devonian period, coelacanths thrived and adapted to diverse ecological roles. While most were sluggish marine hunters that likely ambushed their prey, one fossilized coelacanth, Rebellatrix divaricerca, discovered in 2012, was a fast, agile predator. This streamlined fish, with its distinctive forked tail, hunted smaller creatures across vast distances in the ancient seas of British Columbia around 250 million years ago. Another remarkable species, Megalocoelacanthus, reached lengths of up to 10 feet and lacked teeth. Some coelacanths even transitioned from the ocean to freshwater habitats [PDF], where they may have crossed paths with dinosaurs.
4. UNTIL 1938, SCIENTISTS BELIEVED ALL COELACANTHS WERE EXTINCT.
Coelacanths, both ancient and modern, belong to an entire order of fish. For a century, paleontologists thought this entire group vanished alongside the dinosaurs (birds notwithstanding) around 66 million years ago. However, just before Christmas in 1938, a trawler in the Indian Ocean caught an unusual fish in its nets. The vessel, the Nerine, was under the command of Hendrik Goosen, who initially paid little attention to the peculiar catch. The Nerine continued its journey to a fish market in East London, South Africa. Upon arrival, Goosen, as usual, contacted Marjorie Courtenay-Latimer.
Courtenay-Latimer, a local museum curator, had developed a friendship with the captain, who often invited her to inspect his catches for unusual specimens. On that fateful day in 1938, she almost declined due to her busy schedule preparing a new fossil exhibit. Ultimately, she decided to visit, if only to extend holiday greetings to the crew.
She later described the moment: "I cleared away the layers of slime to uncover the most stunning fish I had ever seen. It measured 5 feet long, with a pale mauve-blue hue and faint white speckles, shimmering with an iridescent silver-blue-green glow. Its body was armored with hard scales, and it boasted four limb-like fins and an unusual puppy-like tail. It was exquisite, resembling a large porcelain ornament, but I had no idea what it was." Courtenay-Latimer preserved the specimen, had it stuffed, and reached out to the renowned chemist and ichthyologist J.L.B. Smith. Two months later, he confirmed the fish was a living coelacanth. In her honor, Smith named the species Latimeria chalumnae.
5. TWO LIVING SPECIES ARE NOW KNOWN TO EXIST.
Latimeria chalumnae, often called the West Indian Ocean coelacanth, can grow over 6 feet long. This metallic-blue predator inhabits the waters near South Africa, Madagascar, Mozambique, and the Comoro Islands. A deep-sea dweller, it typically resides at depths of 300-1000 feet, though it has been found as deep as 2000 feet. These fish primarily hunt at night, retreating to underwater caves during the day, where they gather in groups of up to 16 individuals.
A smaller, brown-colored species known as the Indonesian coelacanth (Latimeria menadoensis) was discovered in the late 1990s. This elusive fish remains poorly understood, with only a few specimens ever recorded. Currently, both Latimeria species face significant threats. The West Indian Ocean coelacanth is listed as critically endangered, while its Indonesian counterpart is classified as vulnerable by the International Union for Conservation of Nature (IUCN). If these species disappear, the entire coelacanth order could vanish permanently.
6. COELACANTHS HAVE A REMARKABLE MOUTH STRUCTURE ...
Coelacanths possess a unique intracranial joint located behind their eyes, which divides the skull into two parts. This joint allows the snout to pivot upward when the fish opens its mouth, enabling it to take exceptionally large bites. As biologist Hugo Dutel explains in this video, the joint and its associated muscles "[increase] the overall bite force during prey capture." It’s best to keep your hands clear of those formidable teeth.
7. ... AND VESTIGIAL LUNGS.
CT scans reveal that coelacanth embryos begin developing lungs early in their prolonged gestation. However, as they mature, lung growth slows, and the organs eventually become non-functional in adults. Interestingly, flexible plates encase these obsolete lungs in mature Latimeria, a feature also observed in some coelacanth fossils.
8. OCCASIONALLY, THESE FISH SWIM IN A NOSE-DOWN POSITION.
At the 0:55 mark in the video above, you’ll notice an intriguing behavior. Wild coelacanths have frequently been observed assuming what is often called a “headstand posture.” They tilt their bodies downward, positioning their snouts perpendicular to the seabed, and maintain this stance for up to two minutes. The reason behind this behavior remains unclear, though some researchers speculate it may assist the fish in locating prey.
9. COELACANTHS MAY PRACTICE MONOGAMY.
While the details of coelacanth reproduction are not fully understood, it is known that fertilization occurs internally. In 2013, a German research team examined two pregnant Latimeria chalumnae specimens. DNA analysis showed that each brood had been fathered by a single male, a finding that surprised the scientists.
“For both [of our specimens], it was evident that only one male was involved,” Dr. Kathrin Lampert, a biologist involved in the study, explained to New Scientist. Initially, the team expected the eggs to have been fertilized by multiple males, as this would enhance genetic diversity within the offspring.
“Monogamous mating systems are typically observed in species where males contribute to parental care or where polygamy is impractical,” Lampert’s team stated in their report. They suggested that female coelacanths might conserve energy by mating with only one partner per breeding season.
10. ADULTS REDEFINE THE PHRASE “FAT-HEAD.”
As coelacanths age, their brain tissue grows at a slower pace compared to the rest of their body. In mature adults, the brain occupies less than 1.5 percent of the cranial cavity, with the remaining space filled by fat. In contrast, juveniles have relatively larger brains and less fat in their skulls.
11. A RENOWNED HEMATOLOGIST ONCE COMPOSED A COELACANTH OPERETTA.
On September 10, 1975, a preserved coelacanth at the American Museum of Natural History, which had been there since 1962, was dissected. The procedure was initiated when hematologist Charles Rand of Long Island University requested spleen samples. Dr. Rand, along with paleontologist Bobb Schaeffer and ichthyologists James Atz and C. Lavett Smith, performed the dissection.
A remarkable discovery awaited beneath its skin. Inside this deceased sarcopterygian, the researchers uncovered five embryonic coelacanths. These unborn offspring demonstrated that, unlike the majority of fish, the extraordinary Latimeria chalumnae delivers live young.
Thrilled by this revelation, Rand turned to poetry—or rather, opera. With a playful flair reminiscent of "Weird Al" Yankovic, the musically talented hematologist penned lyrics for an operetta named A Coelacanth’s Lament, or Quintuplets at 50 Fathoms Can Be Fun. His verses were adapted to tunes from Gilbert and Sullivan, including “Tit Willow” from their 1885 comic opera The Mikado. Thankfully, the AMNH has shared some of Rand’s work. Enjoy.
