Page 10 - Amphibian

Ancient amphibians

The first amphibians appeared on earth
during the Devonian period some 360
million years ago. Their closest ancestors
were fishes with fleshy, lobed fins that
TOAD IN THE HOLE looked like legs. Some of these
This toad is not a
fossil – it is mummified. amphibians, like Ichthyostega, had fishlike
When it was tiny, features. Like their ancestors, they may
the toad entered this
hollow stone (found in have been attracted onto land by a good
England in the 1890s) supply of food and fewer enemies to prey
via a small hole at one
end, but eventually it on them (pp. 58–59). Amphibians’
died from a lack of ancestors had lungs for breathing air,
food, water, and air.
and eventually their lobed fins
developed into efficient walking limbs so they were
able to walk around on land.
Amphibians thrived from
the Devonian to the Permian
periods, when they were
more varied in size and
shape than they are today.
Diplocaulus, for example, Short One half of
hind
was quite small, but Eryops leg Triadobatrachus
grew to 6.5 ft (2 m) or more. Artist’s reconstruction of fossil sandwich
Triadobatrachus
Most amphibians had become
FISHY FINS
extinct by the Triassic period, These are reconstructions of
leaving only a few – such as lchthyostega, an early
Triadobatrachus and Rana pueyoi amphibian from the
Devonian period in
– to evolve into modern Skeleton of Greenland. It had some
fishlike features, like a
amphibians (pp. 42–49). Ichthyostega tail fin and small scales, in
its distinctly amphibian
body but had legs
suitable for walking
and fewer skull
bones than a fish.
Reconstruction
TIME CHART OF THE EARTH of Ichthyostega
PERIOD NEWTS,
(Millions EARLY salaman­ FROGS
of years amphib­ CAECILIANS DERS, AND AND
ago) IANS SIRENS TOADS
PALEOCENE
TO PRESENT Only
DAY caecilian
fossil
( 0) •
CRETACEOUS Earliest
(140) Known Earliest
salamander known
JURASSIC • frog
(190) •
TRIASSIC
(225) •
PFRMIAN Eryops Triadoba­
(270) • trachus AMPHIBIAN CROCODILE
• Sharp teeth of This skeleton is of Eryops, a crocodile-
CARBONIFEROUS Ichthyo­ a meat eater
(350) stega like amphibian that lived in swamps
Duration in Texas during the Permian period.
of each
DEVONIAN Skeleton These terrestrial creatures used their
(400) period not
to scale of Eryops strong limbs to move around on land.