Cow Sharks or Hexanchiformes

Cow sharks, scientifically classified under the family Hexanchidae, represent a distinctive group characterized by unique features, including an additional pair or pairs of gill slits. This family encompasses a diverse array of species, totaling 37, and is further organized into 10 genera, each contributing to the fascinating diversity within this ancient shark lineage.

The distinguishing feature of the Hexanchidae family is the presence of additional gill slits, setting them apart from other shark families. While most sharks possess five pairs of gill slits, cow sharks boast an extra pair or pairs, contributing to their unique respiratory system.

Exploring The Genera Of Cow Sharks

1. Gladioserratus

Characteristics: Limited information is available about Gladioserratus, and it appears to be a less-studied genus within the cow shark order. More research is needed to understand its specific characteristics and ecological role.

2. Heptranchias

Notable Species: The Sharpnose Sevengill Shark (Heptranchias perlo).

Characteristics: Heptranchias is known for its seven gill slits, distinguishing it from sharks with the more common five gill slits. It typically inhabits deep-sea environments.

3. Hexanchus

Notable Species: Bluntnose Sixgill Shark (Hexanchus griseus).

Characteristics: Hexanchus species have six gill slits, marking a primitive trait among cow sharks. They often occupy a wide range of depths, including deep-sea and nearshore environments.

4. Notidanodon

Notable Species: Limited information is available about specific species within Notidanodon.

Characteristics: The genus Notidanodon is relatively less studied, and further research is required to understand its distinct features and behavior.

5. Notorynchus

Notable Species: Broadnose Sevengill Shark (Notorynchus cepedianus).

Characteristics: Known for its broad snout and seven gill slits, Notorynchus species often inhabit coastal and continental shelf areas. They exhibit a preference for both deep and shallow waters.

6. Pachyhexanchus

Notable Species: Limited information is available about specific species within Pachyhexanchus.

Characteristics: Pachyhexanchus is a less-documented genus, and additional research is necessary to provide detailed insights into its morphology and behavior.

7. Paraheptranchias

Notable Species: The Sharpnose Sevengill Shark (Paraheptranchias tenuis).

Characteristics: Paraheptranchias species share similarities with Heptranchias, including the distinctive feature of seven gill slits. Research on this genus is ongoing.

8. Pseudonotidanus

Notable Species: Limited information is available about specific species within Pseudonotidanus.

Characteristics: Pseudonotidanus is a lesser-known genus within the cow shark order, and more studies are needed to uncover its unique characteristics.

9. Welcommia

Notable Species: Limited information is available about specific species within Welcommia.

Characteristics: Welcommia is a relatively obscure genus, and scientific exploration is required to understand its distinct features and ecological role.

10. Weltonia

Notable Species: Limited information is available about specific species within Weltonia.

Characteristics: Weltonia is a less-studied genus within the cow shark order, and comprehensive research is necessary to elucidate its morphology and behavior.

Geographical Distribution of Cow Sharks:

Cow sharks are found in various oceanic regions, demonstrating adaptability to a range of environments. Key distribution areas include deep-sea habitats, continental shelves, and coastal waters. Species within the genera Hexanchus and Notorynchus, for instance, can be encountered in both cold and temperate waters worldwide.

Physical Appearance of Cow Sharks:

  1. Gill Slits: One defining characteristic of cow sharks is their gill arrangement. Most species have either six or seven gill slits, in contrast to the more common five found in many other shark species.
  2. Body Structure: Cow sharks typically have stout bodies, often featuring broad heads and unique snout shapes. The genus Hexanchus, for instance, is known for its characteristic blunt snout.
  3. Size: Sizes vary among species, with some reaching considerable lengths. The Bluntnose Sixgill Shark (Hexanchus griseus), for instance, can grow up to 16 feet (4.9 meters).

Food and Diet of Cow Sharks:

  1. Versatile Predators: Cow sharks are opportunistic predators with varied diets. Their menu may include fish, squid, crustaceans, and other marine organisms.
  2. Scavenging Behavior: Some species, such as the Bluntnose Sixgill Shark, exhibit scavenging behavior. They are known to feed on carcasses and utilize their keen sense of smell to locate prey.

Mode Of Reproduction of Cow Sharks:

  1. Ovoviviparity: Cow sharks are primarily ovoviviparous, meaning they give birth to live young. Fertilized eggs develop inside the female’s body before the hatching of pups. This reproductive strategy contributes to the survival of offspring in varied marine environments.

Conservational Status of Cow Sharks:

  1. Near Threatened: Certain cow shark species, like the Broadnose Sevengill Shark (Notorynchus cepedianus), have been classified as near-threatened by the IUCN. Threats include habitat modification, overfishing, and bycatch in various fisheries.
  2. Fishery Impact: Cow sharks may face challenges due to targeted fisheries or unintentional capture in commercial fishing operations.

Some Interesting Facts About Cow Sharks

  1. Ancient Lineage: Cow sharks belong to an ancient lineage of sharks, with roots tracing back millions of years. Their unique features hint at a long and complex evolutionary history.
  2. Adaptations: The cow shark’s distinct gill slit arrangement and body structure showcase adaptations to different ecological niches, allowing them to thrive in diverse marine ecosystems.
  3. Research Gaps: Despite their intriguing characteristics, some cow shark genera, such as Pachyhexanchus and Welcommia, remain understudied. Addressing these research gaps is crucial for a comprehensive understanding of their biology.

5 Main Types of Cow Sharks

The Hexanchidae family, commonly known as cow sharks, comprises various intriguing species, each with its distinct characteristics. Here, we delve into the specifics of five notable cow shark species, shedding light on their traits and ecological significance.

1. Sharpnose Sevengill Shark (Heptranchias perlo):

  • Gill Slits: As the name suggests, the sharpnose sevengill shark possesses seven gill slits, distinguishing it within the family.
  • Habitat: Found in deep-sea environments, these sharks are known for their adaptability to a range of depths.
  • Behavior: Considered elusive, they navigate the ocean depths, showcasing a blend of mystery and evolutionary resilience.

2. Bluntnose Sixgill Shark (Hexanchus griseus):

  • Gill Slits: Featuring six gill slits, the bluntnose sixgill shark is a representative of the broader sixgill shark category.
  • Distribution: Exhibits a global presence, inhabiting both deep and shallow waters, showcasing their versatility.
  • Ecological Role: As apex predators, they play a crucial role in regulating marine ecosystems, contributing to overall biodiversity.

3. Bigeyed Sixgill Shark (Hexanchus nakamurai):

  • Gill Slits: Similar to the bluntnose sixgill shark, this species boasts six gill slits, a characteristic of Hexanchidae sharks.
  • Eyes: Notable for its large, luminous eyes, adapted for low-light environments in the deep sea.
  • Feeding Habits: Primarily a scavenger, the bigeyed sixgill shark relies on its keen senses to locate and consume prey in the dark depths.

4. Broadnose Sevengill Shark (Notorynchus cepedianus):

  • Gill Slits: Possessing seven gill slits, the broadnose sevengill shark is known for its distinctively broad snout.
  • Habitat: Often found in coastal and continental shelf areas, showcasing adaptability to varying marine environments.
  • Reproductive Strategy: Exhibits ovoviviparity, where eggs hatch inside the mother, and live young are born, contributing to their reproductive success.

5. Atlantic Sixgill Shark (Hexanchus vitulus):

  • Gill Slits: Maintaining the six gill slit characteristic, the Atlantic sixgill shark is a species within the broader sixgill shark group.
  • Size: Relatively small compared to other Hexanchidae members, showcasing diversity within the family.
  • Geographical Range: Primarily found in the Atlantic Ocean, contributing to the regional biodiversity of shark species.

Significance and Conservation:

While cow sharks are not typically targeted in commercial fishing, some species may face threats such as bycatch or habitat changes. Conservation efforts focus on understanding each genus’s ecology and implementing measures to protect their habitats.


Cow sharks, belonging to the order Hexanchiformes, are a unique and ancient group of elasmobranchs. With distinct features and a rich evolutionary history, these sharks offer a fascinating glimpse into the diverse marine ecosystems they inhabit

Intriguingly, the Hexanchidae family, with its additional gill slits and ancient lineage, offers valuable insights into the evolutionary history of sharks. Ongoing research contributes to our understanding of these fascinating creatures and their roles in maintaining the health of marine ecosystems.



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