We must not think of the
smooth-skinned frogs and toads and innocent newts which to-day
represent the fallen race of the Amphibia. They were then heavily
armoured, powerfully armed, and sometimes as large as alligators
or young crocodiles. It is a characteristic of advancing life
that a new type of organism has its period of triumph, grows to
enormous proportions, and spreads into many different types,
until the next higher stage of life is reached, and it is
dethroned by the new-comers.
The first indication--apart from certain disputed impressions in
the Devonian--of the land-vertebrate is the footprint of an
Amphibian on an early Carboniferous mud-flat. Hardened by the
sun, and then covered with a fresh deposit when it sank beneath
the waters, it remains to-day to witness the arrival of the
five-toed quadruped who was to rule the earth. As the period
proceeds, remains are found in great abundance, and we see that
there must have been a vast and varied population of the Amphibia
on the shores of the Carboniferous lagoons and swamps. There were
at least twenty genera of them living in what is now the island
of Britain, and was then part of the British-Scandinavian
continent.
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