Cow Shark Facts

Short video of diving with sevengill cow sharks near Cape Town, South Africa.

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Cow Shark Details: Origins, Description, and Habits

Origins of Cow Sharks

Cow sharks have a long fossil record. The genus Hexanchus first appears in the Late Cretaceous, while Notorynchus first appears in the Late Paleocene. In overall body plan, these sharks have changed relatively little over tens of millions of years, which is why they are often described as primitive-looking sharks.

Description of Cow Sharks

Cow sharks have a distinctive body shape. They have only one dorsal fin, positioned toward the back of the body, and lack the large central dorsal fin seen in most familiar sharks. They also have round, blunt snouts. Sixgill sharks have six gill slits, while sevengill sharks have seven gill slits. The sixgill shark is dark gray to brown with a lighter underside, while the sevengill shark has numerous small dark spots on the dorsal surface.

Differences and Behavior between Cow Sharks

Although sixgill and sevengill cow sharks appear similar, they occupy different ecological niches. The larger bluntnose sixgill is mainly a nocturnal deep-water shark, often reported from depths of 100 to 600 fathoms (Castro, p. 27). Broadnose sevengill sharks, on the other hand, prefer shallower nearshore waters and are often reported from depths of 3 to 6 fathoms (Castro, p. 39). Sevengills feed on fish, other sharks, rays, and marine mammals, and have been observed hunting in groups.

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Cow Shark Tooth Morphology and Fossil Tooth Identification

Notorynchus cepedianus Tooth Identification

Hexanchus griseus Tooth Identification

Symphyseal Teeth

Cow Shark Tooth Positions

Fossil cow shark teeth are difficult to confuse with most other shark genera because of their unusual shape. Lower lateral teeth are broad and rectangular, with a primary cusp followed by multiple smaller cusplets that decrease in size toward the distal end. The mesial edge in front of the primary cusp usually has serrations. Upper teeth are generally more square-shaped, have fewer cusps, and often lack serrations on the mesial edge. Cow sharks also have a distinctive fan-shaped lower symphyseal tooth.

Hexanchus vs. Notorynchus Teeth: Identification Differences

Even though cow shark teeth are easily separated from most other shark teeth, Hexanchus and Notorynchus teeth can be difficult to distinguish from each other. In general, Hexanchus teeth are larger and more robust. Typical Hexanchus lower lateral teeth are about 32-38 mm (1.25-1.5 in), while Notorynchus cepedianus teeth are usually closer to 25 mm (1 in) (Cocke, p. 82-83). Notorynchus typically has fewer distal cusplets behind the primary cusp, while Hexanchus can have many more. The mesial serrations also differ: Hexanchus has very fine serrations, while Notorynchus generally has larger, recurved serrations.

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High Quality Shark Teeth by Fossilera

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Fossil Examples of Cow Shark Teeth and Fossil Hunting Locations

Fossil cow shark teeth are uncommon but occur in many Miocene and Pliocene marine formations. Productive fossil collecting regions include the Chesapeake Bay area, especially the Calvert Cliffs of Maryland; North Carolina, including the Aurora fossil site; and Florida fossil sites such as Venice Beach.

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Hexanchus cf. collisonae
Eocene Sixgill Cow Shark

Hexanchus cf. collisonae is an Eocene cow shark. These fragile fossil teeth were formerly referred to as Hexanchus agassizi by some collectors and older references.

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Hexanchus griseus (Bonnaterre, 1788)
Bluntnose Sixgill Cow Shark

Hexanchus griseus is a living sixgill cow shark. Fossil teeth assigned to this form first appear in the Miocene. Hexanchus teeth can usually be separated from Notorynchus teeth by their larger size, finer mesial serrations, and greater number of cusplets along the lower lateral teeth.

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Notorynchus cepedianus (Péron, 1807)
Broadnose Sevengill Cow Shark

Purdy et al. (2001) considered these fossil teeth identical to the living broadnose sevengill, Notorynchus cepedianus, making N. primigenius synonymous with the extant species.

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References / Scientific Sources

Castro, Jose L. (1996). Sharks of North American Waters. College Station: Texas A&M University Press.

Cocke, Joe. (2002). Fossil Shark Teeth of the World.

Kent, B.W. (2018). The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland. In: The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA. Smithsonian Contributions to Paleobiology, No. 100.

Purdy, R., Schneider, V., Appelgate, S., McLellan, J., Meyer, R. & Slaughter, R. (2001). The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, Aurora, North Carolina. In: Geology and Paleontology of the Lee Creek Mine, North Carolina, III. C. E. Ray & D. J. Bohaska eds. Smithsonian Contributions to Paleobiology, No. 90. Smithsonian Institution Press, Washington D.C. pp. 71-202.

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