Return to - Fossil Gallery - Fish - Sharks, Skates, & Rays

Cow Shark Comparison

NOTORYNCHUS (Ayres, 1855)
&
HEXANCHUS (Rafinesque, 1810a)

The Cow Sharks


Shark Info Tooth Morphology Fossil Examples



Information


Cow Sharks

Cow sharks probably made their first appearance in the Cretaceous as the Hexanchus genus, while the Notorynchus genus first appeared in the late Paleocene. Today, there are two extant cow sharks, N. cepedianus (the Sevengill Cow Shark), and H. griseus (the Sixgill Cow Shark).

Cow sharks in general have a characteristic appearance in that they only have a single dorsal fin and round, blunt snouts. The sixgill shark has (you guessed it) six gill slits, while the sevengill shark has (right again) seven gill slits. Sixgill sharks are also larger than sevengill sharks. Sixgill sharks have been known to reach lengths up to 4.82 m (15.8 ft) (Castro, p. 27), while sevengill sharks have been known to reach lengths of up to 2.64 m (8.7 ft) (Castro, p. 39). Also the sixgill shark has a dark gray to brown color, with a lighter underside, while the sevengill shark has numerous small dark spots on the dorsal surface.

Although they appear similar, these two sharks occupy different ecological niches. The larger sixgill shark is primarily a nocturnal deep water shark often reported from depths of 100 – 600 fathoms (1 fathom = 6 ft = 1.8 m) (Castro, p. 27). They have a worldwide distribution in temperate and tropical waters. It feeds on crustaceans and a wide array of fishes. Sevengill sharks, on the other hand, are aggressive sharks that prefer shallow near shore waters. They are often reported from depths of 3 – 6 fathoms (Castro, p. 39). They are found throughout the Indian and Pacific oceans, and feed on a variety of prey, from fish, including other sharks, to marine mammals.

Tooth Morphology




Lower lateral Notorynchus cepedianus tooth from Calvert Co., MD



Lower lateral Hexanchus griseus tooth from Aurora, NC.


Due to their self-evident shape, Cow shark teeth are nearly impossible to confuse with other shark genera. Lower laterals have a unique rectangular shape lined with cuspls, which become smaller toward the distal end. In front of the first cusp, or primary cusp, on the mesial edge, are serrations. The roots are generally thin and rectangular shaped. Uppers are generally more square-shaped than the lowers, have less cusps, and often lack serrations on the mesial edges. Upper parasymphyseal teeth (front teeth) consist of a single angled cusp and a narrow root. Cow sharks also have a unique lower symphyseal tooth (center tooth). These teeth are fan shaped. Refer to the following image for examples of upper and lower teeth.


This image shows Notorynchus cepedianus upper and lower teeth from the Calvert Cliffs of MD. Notice the lower symphyseal tooth.


There are also some differences between male and female teeth. These differences, however, will not be discussed here.

Even though Cow shark teeth are easily differentiated from other shark genera, H. sp. and N. cepedianus can be very difficult to distinguish from each other. There are small differences between the teeth, most of which are beyond the scope of this webpage. However, here are a few general guidelines to follow. To start, H. sp. is a larger, more robust, version of N. cepedianus. The typical size of H. sp is around 32-38 mm (1.25 – 1.5 inches), while N. cepedianus is slightly smaller, around 25 mm (1 inch) (Cocke, p. 82-83). There are two key differences between the two sharks lower lateral teeth. N. cepidianus has less cusps that run behind the primary cusp. Typically there are around 5 or 6 cusps on N. cepedianus, while H. sp. has up to 13 cusps (Kent, p.18). The second difference lies in their mesial edges. H. sp. has very fine serrations on the mesial edge, while N. cepedianus has larger recurved serrations on the mesial edge. A comparison of the shoulders is shown in the image below.


This image shows a comparison between lower lateral Notorynchus and Hexanchus serrations on the mesial edge. Hexanchus has very fine serrations, while Notorynchus generally have larger, curved serrations.



The Fossils

Hexanchus cf. collisonae, Hexanchus griseus

Notorynchus cepedianus
(Cow Sharks)



Haxanchus cf. collisonae
(Sixgill Cow Shark)
This use to be called H. agassizi.
These teeth are very fragile and hard to find. This is a lower lateral tooth.
H. agassizi is an Eocene cow shark.

Formation:Nanjemoy Formation, Potapaco Member, Bed B
Age:Lower Eocene (Ypresian), ~55 m.y.
Location:Fisher Lane Bone Bed, Fisher Branch of Muddy Creek, Staffod Co., VA
Size: ~"5/8 long (15mm)


Hexanchus griseus (Bonnaterre, 1788) aka Hexanchus gigas (Sismonda, 1857)
Sixgill Cow Shark
Cow sharks are very primitive sharks, and look almost as weird as their teeth. Cow sharks lack the many dorsal fins on their backs that most sharks have. Instead, they only have a single dorsal fin toward their tail. They are also very wide and bulky.
Two Genus of cow shark are found at the mine. Hexanchus is the less common genus.
H. griseus is a living species today. The fossil teeth are probably from this extant species and first appeared in the miocene.

Hexanchus teeth can be easily differentiated from Notorynchus teeth. Notorynchus teeth have serrations on their mesial edge, whereas Hexanchus teeth have very fine serrations on the mesial edges. Also Hexanchus teeth tend to have more cones running down the length of the tooth.
This is an outstanding lower Hexanchus tooth.

Click on the image to see it when found.

Formation:
  • Yorktown
    Age:
  • Roughly 2.5-5 m.y.
    Location:
  • PCS Mine, Aurora, NC
    Size:
  • ~ 1 5/8" (41mm) Date:
  • Feb. 2009 TRIP
    • The teeth of this shark are fragile and are often found broken, like the one in this image. Sadly, the conules are missing on this specimen.

    Formation:Yorktown
    Age:Pliocene: ~ 2.5-5 m.y.
    Location:PCS Mine, Aurora, NC
    Size:~ 1 1/8"" (27mm)
    Date: March 2008 TRIP


    Notorhynchus cepedianus (Peron, 1807) aka primigenius (Agassiz, 1843)
    Sevengill Cow Shark
    Identification based on Kent (1994) & Purdy et al (2001).
    Purdy et al (2001) believe these teeth are identical to the extant N. cepedianus, and therefore N. primigenius is just synonymous to N. cepedianus.
    Cow sharks are very primitive sharks, and look almost as weird as their teeth. Cow sharks lack the many dorsal fins on their backs that most sharks have. Instead, they only have a single dorsal fin toward their tail. They are also very wide and bulky.
    This species is extant today, but rare. They are active in shallow waters and are very aggressive. They can get up to 10 feet in length. Their diet consists of mainly other sharks, rays, bony fish, and seals.

    Two genera of cow shark are found at the mine. The more common Notorynchus, and the less common Hexanchus. Notorynchus teeth can be easily differentiated from Hexanchus teeth. Notorynchus teeth have serrations on their mesial edge, whereas Hexanchus teeth have very fine conules on the mesial edges. Also Hexanchus teeth tend to have more cones running down the length of the tooth.
    N. cepedianus teeth are common in both the Pungo River and Yorktown formations.
    Their roots are fragile and are often found broken, as the two lateral teeth in the image show.

    Formation:
  • Pungo River and/or Yorktown
    Age:
  • Roughly 2.5-5 or 18-22 m.y.
    Location:
  • PCS Mine, Aurora, NC
    Size:
  • largest one is 1 3/4" (44mm)
    • N. cepedianus
    Here is a beautiful complete cow shark


    Formation:
  • Pungo River
    Age:
  • Roughly 18-22 m.y.
    Location:
  • PCS Mine, Aurora, NC
    Size:
  • ~1" (25mm)
    Date:
  • Sept 2008 TRIP
    • Click to view the fossil as found
    N. cepedianus
    Here is another complete cow shark

    Click on the image to see it as found.

    Formation:
  • Pungo River
    Age:
  • Roughly 18-22 m.y.
    Location:
  • PCS Mine, Aurora, NC
    Size:
  • ~1" (25mm)
    Date:
  • March 2008 TRIP
    • Click to view the fossil as found
    N. cepedianus
    And yet another complete one

    Click on the image to see it as found.

    Formation:
  • Pungo River and/or Yorktown
    Age:
  • Roughly 2.5-5 or 18-22 m.y.
    Location:
  • PCS Mine, Aurora, NC
    Size:
  • ~ 1 1/8" (27mm)
    Date:
  • March 2006 TRIP
    • N. cepedianus
    Another example tooth


    Formation:
  • Yorktown
    Age:
  • Roughly 2.5-5 m.y.
    Location:
  • PCS Mine, Aurora, NC
    Size:
  • ~ 1 1/8" (27mm)
    Date:
  • Feb 2009 TRIP

    • This is my best Notorynchus tooth to date. It is nearly perfect, and was plucked straight from a clay block.

    Click on the pic to see the trip this was found on.

    Formation:
  • Choptank, Zone 17?
    Age:
  • Middle Miocene ~ 15 m.y.
    Location:
  • Near Willows and Randle Cliffs, Calvert Co., MD
    Size:
  • This nice specimen is approximately 1" (25mm)
    Date:
  • June 2006 TRIP
    • This image shows different tooth positions of Notorynchus

    Formation:
  • Calvert, Plum Point member
    Age:
  • Early - Middle Miocene ~ 18-15 m.y.
    Location:
  • Near Willows and Randle Cliffs, Calvert Co., MD
    Size:
  • Big broken lateral is about 1" (25mm)

    • Notorhynchus teeth are commonly found broken, such as the teeth in this pic.

    Formation:
  • Calvert
    Age:
  • Early - Middle Miocene ~ 18-15 m.y.
    Location:
  • various places, Calvert Co., MD
    Size:


    • References Page