- SHARKS AND THEIR KIN
Efficient killers from way back - Class Chondrichthyes
Sharks are one of nature’s great success stories.
Since their appearance 400 mya, they have changed little, merely
improving their ability to hunt and feed through evolving more
resiliant tooth stuctures and more streamlined body shapes. The
basic body plan underwent two successful major modifications:
one in the Carboniferous Period, when the holocephalans (chimaeras
and rabbitfishes) first appeared; and one in the Jurassic Period,
when the flattened rays evolved. Today, sharks, rays and holocephalans
are known from 800-plus species, including the largest fish on
earth, the gentle whale shark, which grows up to 15 m. Huge predators
such as the Great White shark, today reach lengths in excess
of 7 m, but only 2 mya voracious sharks grew up to 15 m long
- with 18 cm teeth to match - the most gruesome underwater death
machines that ever lived.
Summary by Dr. Irwin Haydock of the book entitled
The Rise of Fishes, 500 million years of evolution, by John A.
Long, Johns Hopkins University Press, 1995. (See Chapter 3)
If you would like to learn more about the evolution
of fishes, we recommend Long's excellent book. It's loaded with
information, well written and easy to understand.
- Fossil Shark Teeth - Genus Carcarocles
- Click images to zoom
Sharks are members of the class Chondrichthyes (cartilaginous
fishes). Although there are numerous skeletons of bony fish preserved
in ancient sediments, the conditions were seldom right for the
preservation of shark bodies which contained only cartilage and
flesh. For the most part, only the teeth of these ancient marine
giants were preserved.
Listed here beginning with the oldest of the extinct
sharks of the genus Carcarocles.
 Eocene
(45-36 million years ago) Carcharocles ariculatus, Santee
Limestone, Dorchester-Orangeburg counties, South Carolina. Ancestor
of the Carcharocles angustidens and Carcharocles megalodon.
Ariculatus means uneven serrations. The serrations start
coarse at the base and get finer toward the tip. Carcharocles
ariculatus has more bulbous rounded root.
Oligocene to early miocene (28.5 to 23 million years
ago) Carcharocles angustidens (Shown here on the right)
Chandler Bridge Formation, Summerville, Dorchester County, South
Carolina, more angular defined root.
Middle miocene (15 to 20 million years ago) the shark
Chubatensis, ancestor of the meglodon is considered the
transition from angustiden to meglodon. Chubatensis has
a very minimal cusp compared with it's ancestor angustiden.
 Miocene
Epochs to Pliocene (2 to 15 million years ago) formerly known
as Carcharodon megalodon now more correct naming Carcharocles
megalodon, Hawthorne Formation, Coastal South Carolina. The
name Carcharodon is now relegated to the modern White Shark which
previously was believed to be a descendant but is now viewed
as parallel relative of the now extinct Carcharocles megalodon.
The Carcharocles megalodon tooth seen here
on the right is over 6 inches long. By reconstructing the jaws
of these creatures from the huge 6 and 7 inch teeth that have
been found, scientists have created a glimpse of an awesome scavenger
of the ancient oceans of the earth.
This giant shark was thought to reach as large as
40 to 60 feet long, weighing up to 40 tons. It had 5 rows of
teeth in the upper jaw containing 28 teeth in each row. There
were 5 rows in the lower jaw containing 30 teeth in each row
for a total of 290 teeth.
As big as a school bus, this creature could have swallowed a
bass boat with ease.
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