Coelacanth

The coelacanth (Latimeria chalumnae) is an ancient lobe-finned fish and one of only two living species of the genus Latimeria, the sole surviving genus of the order Coelacanthiformes, a lineage once thought to have gone extinct alongside the dinosaurs roughly 66 million years ago. Its dramatic rediscovery off the coast of South Africa in 1938 made it one of the most famous "living fossil" species known to science. Coelacanths are closely related to the ancient lineage that gave rise to the first four-limbed land vertebrates, owing to their fleshy, limb-like paired fins. The species is found in deep marine waters of the western Indian Ocean and is classified as critically endangered.

Coelacanths are unmistakable among living fish:

• Deep blue-gray body marked with scattered white or pale blotches, unique to each individual
• Thick, large, overlapping scales
• Fleshy, lobed paired fins resembling stubby limbs, moved in an alternating gait-like pattern
• A distinctive three-lobed tail fin with a small additional central lobe
• Large, reflective eyes adapted for low light No other living fish shares its combination of limb-like lobed fins and hinged intracranial skull joint, making misidentification essentially impossible. Individual white blotch patterns are distinctive enough that researchers use them to identify specific coelacanths over time.

Coelacanths inhabit deep, rocky marine caves and steep underwater slopes, typically at depths of roughly 150 to 700 meters, in the cool, dark waters of the western Indian Ocean. Known populations occur around the Comoros Islands, the coast of South Africa and Mozambique, and Madagascar, with a distinct related species found near Sulawesi, Indonesia. They favor volcanic cave systems that offer shelter from predators and stable, cool water temperatures throughout the day. Individual fish tend to return to the same resting caves repeatedly, showing strong site fidelity within their deep-slope habitat.

Coelacanths are largely nocturnal drift-hunters, resting motionless in sheltered caves during daylight hours and emerging at night to forage for fish and squid in deeper water. They swim slowly and deliberately, using their paired lobed fins in a coordinated, alternating motion reminiscent of limb movement. The species is ovoviviparous, with females giving birth to live young after an unusually long gestation period lasting well over a year. Coelacanths are slow-growing, long-lived, and reproduce infrequently, making populations especially vulnerable to disturbance.