The coelacanth is a fish called a “living fossil,” as it was long thought to be extinct until its rediscovery in 1938. This event offered a glimpse into a lineage of fishes that has survived for hundreds of millions of years. This ancient fish possesses many unique anatomical features, and its dentition provides insight into the predatory lifestyle of this deep-water dweller.
Jaw and Palate Dentition
The coelacanth’s jaws and the roof of its mouth are armed with multiple rows of sharp, conical teeth. These teeth vary in size, with the largest being fang-like structures up to 10 millimeters high, accompanied by smaller teeth. All are composed of a cone of orthodentine surrounding a pulp cavity and capped by a layer of true enamel, making them sharp and durable for seizing fish.
The arrangement of these teeth on the premaxillary, maxillary, and dentary bones—the main bones of the jaws—is not random. They are situated to hold onto struggling prey. This dental setup is the first point of contact in the coelacanth’s predatory sequence.
Ectopic Oral Denticles
Beyond the jaw teeth, the coelacanth’s mouth is covered in thousands of small, tooth-like oral denticles. These are found ectopically, meaning in an unusual position, on surfaces like the gill arches and various soft tissues. This trait is highly unusual among living vertebrates.
Structurally similar to the larger teeth but much smaller, their function is not for biting but to create a rough, abrasive surface. This texture is effective at gripping slippery prey and preventing its escape. This allows the prey to be controlled and maneuvered towards the esophagus for swallowing.
Feeding and Predatory Behavior
The coelacanth employs a specialized hunting technique known as suction feeding. It possesses a unique intracranial joint, a hinge in its skull not found in other living animals, which allows it to open its mouth extremely wide. By rapidly expanding its oral cavity, the fish creates a powerful negative pressure that sucks in both water and any nearby prey.
Once the prey is drawn into the mouth, the dental structures work to secure the capture. This combination of suction and multi-part dentition allows the coelacanth to be an effective predator on fish and squid in its deep-sea habitat. The entire system is designed not for chewing, but for engulfing prey whole.
The coelacanth is considered a nocturnal drift hunter, conserving energy in caves during the day. It moves slowly near the seabed at night to ambush unsuspecting prey.
Tooth Replacement and Development
Like many fishes, the coelacanth’s teeth are replaced throughout its life. This continuous cycle is a feature of polyphyodont animals, which grow and shed teeth in successive sets to ensure the dental arsenal remains functional.
Studies of coelacanth jaws reveal that replacement occurs in waves that move along the jawline. This systematic process ensures functional teeth are always present, as new teeth develop in the soft tissue adjacent to old ones and erupt to replace them as they are shed.
This ability to regenerate teeth is linked to the coelacanth’s continuous growth. The development of its teeth, from fangs to denticles, is an ongoing process. This lifelong dental renewal is a primitive characteristic that has been retained in this ancient lineage.