Some of them were short and stumpy creatures, a few
inches long, with weak limbs and short tails, and broad,
crescent-shaped heads, their bodies clothed in the fine scaly
armour of their fish-ancestor (the Branchiosaurs). Some (the
Aistopods) were long, snake-like creatures, with shrunken limbs
and bodies drawn out until, in some cases, the backbone had 150
vertebrae. They seem to have taken to the thickets, in the
growing competition, as the serpents did later, and lost the use
of their limbs, which would be merely an encumbrance in winding
among the roots and branches. Some (the Microsaurs) were agile
little salamander-like organisms, with strong, bony frames and
relatively long and useful legs; they look as if they may even
have climbed the trees in pursuit of snails and insects. A fourth
and more formidable sub-order, the Labyrinthodonts--which take
their name from the labyrinthine folds of the enamel in their
strong teeth--were commonly several feet in length. Some of them
attained a length of seven or eight feet, and had plates of bone
over their heads and bellies, while the jaws in their enormous
heads were loaded with their strong, labyrinthine teeth.
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