Among the sharks, the
modern Squalodonts entirely displace the older types, and grow to
an enormous size. Some of the teeth we find in Tertiary deposits
are more than six inches long and six inches broad at the base.
This is three times the size of the teeth of the largest living
shark, and it is therefore believed that the extinct possessor of
these formidable teeth (Carcharodon megalodon) must have been
much more than fifty, and was possibly a hundred, feet in length.
He flourished in the waters of both Europe and America during the
halcyon days of the Tertiary Era. Among the bony fishes, all our
modern and familiar types appear.
The amphibia and reptiles also pass into their modern types,
after a period of generous expansion. Primitive frogs and toads
make their first appearance in the Tertiary, and the remains are
found in European beds of four-foot-long salamanders. More than
fifty species of Tertiary turtles are known, and many of them
were of enormous size. One carapace that has been found in a
Tertiary bed measures twelve feet in length, eight feet in
width, and seven feet in height to the top of the back. The
living turtle must have been nearly twenty feet long.
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