The Mesozoic, or era of middle life, was a long stretch of time during
which there was marvelous development among the reptiles. Many strange
types were produced and most of them became extinct before the end of
the era. The reptilian stock branched out in many directions. Types
emerged which differed from one another so widely that their mutual
relationships have become obscure. Hideous and fantastic creatures
suggesting sea serpents and dragons were worldwide in distribution.
Reptiles of the air and seas acquired large size and weird forms, but
greater advances were made upon land.
The flying reptiles or pterosaurs flourished in Jurassic times with some
of the larger varieties surviving until near the close of the
Cretaceous. Although these winged lizards were the first of the
vertebrates to fly they are not to be confused with birds. They were
without feathers, and the earlier forms were provided with long tails
bearing a flattened rudder-like tip. One of the best known of this type
had a length of about eighteen inches. Its jaws were long and provided
with sharp teeth. The wings were membranes attached to body and legs,
stretched and manipulated by means of greatly elongated fingers. In
later types there was a reduction in tooth equipment and length of tail.
_Pteranodon_, found in Kansas, had a wing spread of twenty-five feet, a
large toothless beak, a short body, and a mere stub of a tail. It was
one of the last of these winged monsters.
Several types of marine reptiles appeared during this era, among them
the plesiosaurs which first appeared in Triassic seas. These peculiar
animals were serpent-like with regard to the character of head, neck,
and tail, but in other respects were quite different, the short
barrel-shaped body being provided with four large paddles corresponding
to the usual limbs of quadrupeds. Fossil remains of these animals are
common in many Jurassic and Cretaceous deposits, some of the largest
exceeding forty feet in length. Mosasaurs, also marine carnivores,
inhabited shallow Cretaceous seas throughout the world and are
especially abundant as fossils in the Kansas chalk beds. These were
elongated forms with a resemblance to salamanders in some respects but
provided with long pointed jaws and sharp teeth. Swimming was
accomplished largely by the tail though probably aided to some extent by
four webbed paddles or flippers. The ichthyosaurs were more fish-like in
construction, as the name implies. The limbs were short and broad, and
there was usually present a well-developed tail-fin as well as a large
fin on the back. They were especially abundant in Jurassic time. Fossils
are fairly common in marine deposits of western North America. Mosasaurs
and ichthyosaurs were about half as long as the plesiosaurs.