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Hemipristis serra from Aurora, NC

HEMIPRISTIS (Agassiz, 1843)

The Snaggletooth Sharks


Shark Info Tooth Morphology Composite Dentition Bite Pathologies Fossil Examples



Information

The Hemipristis genus first appeared in the Eocene as H. curvatus. Their teeth are similar in shape to H. serra but are smaller. This genus is the direct ancestor of H. serra. It disappeared in the Oligocene as the first occurrence of H. serra appeared.

H. serra can be found in Tertiary deposits on the east coast from Maryland to Florida. These beautiful teeth are also a common find in Tertiary deposits worldwide, from both coasts of North and South America to Europe, Africa, and Australia. This shark clearly had a nearly global distribution in the Tertiary. However as the climate changed, from the warmer Miocene into the cooler climate of today, this species became extinct. They are deemed abundant in Miocene exposures. In Pliocene exposures, they are less numerous, and in the Pleistocene, they became restricted to the tropical waters around Indonesia before finally becoming extinct (Kent, p. 79).

H. Serras’ closest living relative is H. elongatus, which continues to swim in the tropical waters of the Eastern Hemisphere today. According to Bonfil, H. elongatus is an inshore and offshore shark with a distribution in the Indian Ocean, western Pacific, from South Africa to China and Australia, including the Red Sea and Gulf of Aden (Bonfil p.15). Sharks from the Hemigaleidae family have a long snouth, with horizontally oval eyes, and internal gill openings, and their first dorsal fin is slightly higher than their second dorsal fin (Compagno, p. 28). They also have a plain color pattern, except for light or dark fin edges or tips on some species (Compagno, p. 28). Figure 2 shows a sketch of H. elongatus.

H. elongatus primarily feed on small bony fish, sharks, and rays. They can reach lengths of up to 2.4 m (Bonfil p. 15). Based on tooth size comparisons between H. elongatus and H. serra, the fossil species could reach sizes between 3 to 5 m (Compagno, p. 486). Therefore, H. serra was most likely a larger version of H. elongatus, it may have looked and behaved similarly.

Teeth

One obvious aspect of H. serra teeth are their unique design. They are easily identifiable from any other tooth. The upper laterals are broad and triangular shaped. They have unmistakable large, course serrations running nearly the length of the blade. The distal serrations tend to be larger than the mesial serrations. Serrations on both sides of the tooth end just before the coronal apex, which is smooth. Upper anterior teeth are narrower than upper laterals. The serrations also run nearly the length of the blade, and end with a smooth coronal apex. They also have a lingual protuberance on the root.

Lower H. serra teeth resemble a different species. They are very similar to sand tiger teeth. In fact, some early literature reports them as different species (Cocke, p. 56). The key to identifying lowers is they have incomplete cutting edges toward the base of the crown. They also have a pronounced lingual protuberance. Lower anterior teeth only have a small number of serrations on each shoulder, while lower lateral teeth are more serrated, superficially resembling the serrations on upper anterior teeth.

Symphysial teeth look quite different. They are very thin, have a large lingual protuberance, and have 1 or 2 serrations on their shoulders. Upper, lower, and symphyseal tooth are shown in the images below.







The Dentition

The following image is a composite dentition from teeth I found along the Calvert Cliffs of Maryland. It was reconstructed using an illustration of the extant snaggletooth dentition in Kent's book "Fossil Sharks of the Chesapeake Bay Region" and also from viewing the dentition in the Aurora Fossil Museum. There are still a few missing teeth in the dentition.





Bite/Feeding Pathologies

Out of 206 sampled teeth, 8 Hemipristis teeth showed signs of feeding and/or bite damage. This translates to roughly 3.8% of Hemipristis teeth. So, chances are most shark tooth collectors have these type of tooth pathologies in their collections.

Most of these damaged teeth have the mesial cutting edges completely sheared off. This type of feeding damage is very easy to recognize. The following image shows six teeth with this specific damage.
A probable reason for this specific damage is when the wide tooth bites into bone, the biting force can easily sheer the fragile serrations off.


This image shows feeding damage to six upper hemipristis teeth. This type of damage is easily recognizable.
Feeding damage from lower Hemipristis teeth can be seen in the image below. Similar to the upper teeth, the blade is sheered off. Notice the smoothness of the sheer on the unworn teeth, unlike a tooth that breaks after fossilization.

Also shown is an upper tooth with bite marks in it. This tooth probably fell out of the sharks mouth and got punctured by a few lower teeth before falling from the shark.

This image shows an upper tooth with puncture marks from the lower teeth, and two lower teeth that have been sheered off.


The Fossils

Hemipristis serra (Agassiz, 1843)
(Snaggeltooth Shark)
Identification based on Kent (1994) & Purdy et al (2001).
This species lived from the late Oligocene into the early Pleistocene. They are commonly called Snaggeltooth Sharks due to the large serrations on their teeth. Species of Hemipristis are extant today, however, they are only found in tropical waters, and are much smaller than the fossil species. The fossil species are also found worldwide.
The center lower is a lingual view, the rest are labial views. The lowers rolled part way onto their sides, making profile views.

As you can see, uppers and lowers are very different.
Formation:
  • Calvert & Choptank
    Age:
  • Miocene ~ 18-15 m.y.
    Location:
  • From various places, Calvert Co., MD
    Size:
  • Largest is 1 1/2" (38mm)
    • These are all lingual views. This is to show the size and shape variation in the Hemi's. The smaller ones are abundant. Larger ones are slightly more difficult to find.
    Formation:
  • Calvert & Choptank
    Age:
  • Miocene ~ 18-15 m.y.
    Location:
  • From various places, Calvert Co., MD
    Size:
  • Largest is 1 3/8" (35mm)
    • Here is a neat pathological hemi. It has a curved blade and a double tip. difficult to find.
    Formation:
  • Calvert or Choptank
    Age:
  • Miocene ~ 18-15 m.y.
    Location:
  • Chesapeake Bay area
    Size:
  • ~1" (25 mm)
    Date:
  • November 2006 TRIP
    • The right upper tooth is a labial view. All others are lingual views.

    Uppers and lowers are generally easy to distinguish form one another.

    The lower rightmost tooth is a symphysial tooth.
    Although these teeth can be found in both the Pungo River and Yorktown formations, the teeth found in the Yorktown are generally larger in size.

    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 9/16" (40 mm)
    These are a couple larger H. serra teeth.

    Formation:Yorktown
    Age:Roughly 2.5-5
    Location:PCS Mine, Aurora, NC
    Size: the complete one has a ~1 13/16" slant" (40 mm) Date:The chipped one was found on the March 2007 Trip


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