Callorhinchus

The elephantfish lives on the dark ocean floor. It has a long, soft snout. The snout helps it find food in the sand. It eats small things like clams.

This fish is often black or brown. It has large fins to help it swim. It also has eyes that can be green.

The fish lays eggs on the muddy bottom. The eggs look like pieces of seaweed. They stay in the eggs for eight months. Then, the tiny fish hatch. They move to deep water to grow.

The plough-nosed chimaera is a strange fish. People also call it the elephantfish. It lives on the ocean floor in the Southern Hemisphere. These fish like muddy or sandy bottoms. They have a long, soft snout. This snout looks like a plough. It helps them find food in the sand. The snout can even sense electric fields!

These fish are not sharks. They have a skeleton made of cartilage. This is the same soft bone found in sharks. However, their jaws are fused to their skulls. This means their jaws are stuck tight. They also have smooth skin. This is different from the tough scales on a shark.

Elephantfish eat small things like clams and jellyfish. They have flat teeth to help them eat. They lay eggs on the ocean floor. The eggs look like pieces of seaweed. They stay in the eggs for eight months. When they hatch, the young fish move to deep water.

The plough-nosed chimaera is a very special fish. Many people call it the elephantfish because of its nose. It lives on the dark ocean floor in the Southern Hemisphere. These fish like to stay on muddy or sandy ground. They are part of a group called holocephalans. This group is different from sharks and rays.

This fish has a unique way of finding food. It has a long, fleshy snout that looks like a plough. This snout helps the fish probe the sea bottom. It can even sense electric fields and movement in the water. The fish uses flat teeth to eat small things. They mostly eat clams and other small shellfish. They also eat jellyfish and tiny octopuses.

Scientists have studied these fish for a long time. The species Callorhinchus callorynchus was named by Linnaeus in 1758. Another species, Callorhinchus milii, was named by Bory de Saint-Vincent in 1823. A third species, Callorhinchus capensis, was named by Duméril in 1865. These fish have a very small genome. This means their genetic code is quite simple. Scientists use them to study how early jaws developed.

There are many interesting facts about their bodies. Their skin is smooth instead of having tough scales. Their jaws are fused directly to their skulls. They have large fins to help them move through water. Their eyes are high on their heads and often look green. The fish lay eggs on the ocean floor. These eggs look like long, flat pieces of seaweed. They stay in the eggs for about eight months.

These fish live in many different places. Some live near South America from Peru to Brazil. Others live near the coasts of Africa, like Namibia. Some are found near Australia and New Zealand. People in South America fish for them all year. They are often sold as whitefish fillets. We must be careful because nets can catch too many. Protecting their home helps them stay safe.

The genus *Callorhinchus* contains a group of unique marine animals known as plough-nosed chimaeras or elephantfish. These creatures belong to the family Callorhinchidae, which is the only living genus in that family. While several extinct genera exist in the fossil record, these living fish are distinct from other chimaeras by their long, flexible, and fleshy snouts. This snout resembles a ploughshare, which is a tool used to turn soil. These fish live on the ocean floor in the Southern Hemisphere, specifically on sandy or muddy substrates. They are significant because they are the only living chimaeras that still inhabit relatively shallow neritic habitats. Most other chimaera groups moved into much deeper waters following the beginning of the Cenozoic era.

The anatomy of a plough-nosed chimaera is highly specialized for life on the sea floor. Their bodies are generally flat, compressed, and elongated. They possess large pectoral fins, which are believed to help them move swiftly through the water. Two dorsal fins are spaced widely apart on their backs, and a spine sits between them. The second dorsal fin is much smaller than the first. Their eyes are positioned high on the head and often appear green. Interestingly, their vision is very poor. To compensate, they rely on their snout to sense movement and electric fields in the water. This electrical sensing allows them to locate prey even in dark or murky environments.

Feeding is a highly specific process for these fish. They are primarily filter feeders that probe the sandy sediment of the ocean bottom. The large protrusion of the snout is the main tool for this task. Once they find prey, they use specialized teeth to consume it. They have three pairs of broad, flat teeth: two pairs in the upper jaw and one pair in the lower jaw. This dental structure is adapted for crushing shellfish. Their diet consists mostly of molluscs, such as clams. They also eat other invertebrates like small octopuses or jellyfish. However, they cannot eat bony fish because they lack the speed of teleosts, which are more active bony fish.

In the study of biology, *Callorhinchus* is a very important research organism. They are the oldest living group of jawed chondrichthyes, a class of fish that includes sharks and rays. While they have a cartilaginous skeleton like a shark, they are classified as holocephalans. This classification distinguishes them from elasmobranchs, the group containing sharks and rays. One major difference is that a shark's jaw is loosely attached to its skull, but a chimaera's jaw is fused to its skull. They also have an operculum, which is a bony cover over their gill slits, and their skin is smooth rather than covered in tough scales. Furthermore, they possess the smallest genome among all chondrichthyans. Because of this, scientists propose using them for entire genome sequencing to represent the whole class of cartilaginous fish.

Reproduction for the plough-nosed chimaera follows a specific seasonal cycle. They are oviparous, meaning they lay eggs. Mating and spawning typically occur during the spring and early summer. During mating, males use claspers near their pelvic fins to transport gametes. They also use a club-like protrusion on their head to hold onto the female. The females release keratinous eggs onto the muddy ocean floor. These egg cases are long and flat, making them look like pieces of seaweed. The eggs change color over time, starting as golden yellow, turning brown, and finally becoming black before hatching. The embryos stay in the eggs for about eight months, using yolk for all their nourishment. Once they hatch, the young instinctively move toward deeper water.

There are three known living species within this genus, each found in different parts of the Southern Hemisphere. *Callorhinchus callorynchus*, named by Linnaeus in 1758, is known as the American elephantfish. It lives in waters ranging from Tierra del Fuego to Peru and southern Brazil. *Callorhinchus capensis*, named by Duméril in 1865, is the Cape elephantfish found off southern Africa. Finally, *Callorhinchus milii*, named by Bory de Saint-Vincent in 1823, is the Australian ghostshark. This species lives in the southwestern Pacific near Australia and New Zealand. During spring and summer, *C. milii* migrates into inshore bays and estuaries to mate.

Human activity has a direct impact on the survival of these species. Currently, there are no specific conservation efforts for the Callorhinchidae family as a whole. However, *Callorhinchus callorynchus* is listed as Vulnerable by the IUCN. This is because they are heavily fished for food in South America, where they are sold as silver trumpeter or whitefish fillets. The greatest threat to these fish is trawling or net fishing, which can catch large numbers very quickly. While some fish are occasionally caught for aquariums, most are taken for the food industry. In Australia and New Zealand, fishing quotas are used to manage the population, but these protections do not reach all areas where the fish live.