similar to a modern hang glider and weighed about as much as the human
pilot. Many pterosaurs had tall crests on their skulls, which possibly functioned
as aforward rudder to steer it in flight.
The pterosaur wings were constructed by elongating the fourth finger of
each forelimb, which supported the front edge of a membrane that stretched
from the flank of the body to the fingertip. The other fingers were left free for
such purposes as climbing trees.By comparison,a bat’s wing is constructed by
lengthening and splaying all fingers and covering them with membrane.
The first reconstructions of a pterodactyl portrayed the animal as an
ungainly glider with leathery wings attached on each side of the body down
to the legs and stretched between a grotesquely elongated finger. Such a large
flap of skin would have made the creature a clumsy walker, shuffling around
on all fours like a bat, not a good way to take off. Later reconstructions showed
a flying reptile with thin birdlike wings attached to the hip, allowing the ani-
mal to walk on two legs, a better design for gaining speed for liftoff.
Why pterosaurs took to the air in the first place remains a mystery.They
apparently arose from tree-dwelling reptiles rather than from running ground
dwellers. Their ancestors might have grown skin flaps for jumping from tree
to tree in a similar manner as flying squirrels. The wing membranes might
have originally served as a cooling mechanism that regulated body tempera-
ture by fanning the forelimbs, and through natural selection they eventually
became flying appendages.
Figure 147The giant
pterosaurs ruled the skies
for 120 million years.JURASSIC BIRDS