Reptiles of the Ancient
(bottom) makes a lucky escape from the jaws of an eighty-foot-long
Lee Krystek, 2000)
Perhaps sea serpents don't exist today, but they
certainly did in prehistoric times. While dinosaurs ruled the
land, their relatives, the great sea reptiles, ruled the ocean.
In 1811 the fossilized skeleton of a monster
was found embedded in a rock. Scientists were confused by what
they saw: the shape of the creature was that of a fish, having
a large dorsal fin on the back and flippers. Other features,
including a long, pointed jaw filled with teeth, seemed more
like a reptile. In the end they decided this strange creature
which they named an Ichthyosaur (meaning "fish-reptile")
was definitely a reptile despite its shape.
The ichthyosaurs were a collection of related
species with the same body-shape. One type, Shonisaurus,
was almost 50 feet in length. Most of the ichthyosaurs were
quite a bit smaller, though, and scientists theorize they may
have behaved much like the porpoises of today. Both porpoises
(which are mammals) and Ichthyosaurs have a teardrop-shaped
torso body, a long snout, short fins up front for steering and
a large crescent-shaped tail fin to drive them forward at speeds
of up to 30 mph (50kph).
Other great swimming reptiles from the days of
the dinosaurs were soon found. The plesiosaur was an
animal very unfish-like in shape. It had a rounded body with
a long tail, long neck and four diamond-shaped flippers to drive
it through the water. The tiny head sported a set of razor-sharp
people think reports of sea monsters might be plesiosaurs
that escaped extinction (Copyright
Lee Krystek, 2000).
Like the ichthyosaurs, plesiosaurs were really
a class of animals with this same basic design. Within this
line developed a wide variety of reptiles. One of these was
the elasmosaurus which grew to a length of 45 feet. Elasmosaurus
had an extremely long neck that allowed it to suddenly reach
out and snap at a prey some twenty feet away.
Another plesiosaur was the Trinacomerium.
Trinacomerium was shorter than other plesiosaurs , with less
neck, a bigger head and larger flippers that allowed it to race
through the water in pursuit of its lunch.
Out of the plesiosaurs came what is perhaps the
greatest carnivore of all time: Liopleurodon. Liopleurodon
was part of a group of short-necked plesiosaurs that became
the pliosaurs. It is difficult to appreciate just how
big liopleurodons grew. Some ran as long as eighty-feet in length
and weighed as much as 100 tons. That's twenty times the weight
of Tyrannosaurus Rex. The head of the biggest liopleurodon's
were thirteen feet long with ten foot jaws. They sported teeth
twice the size of a T-rex. What did a liopleurodon eat? Anything
it wanted. In the prehistoric sea it was the king of the food
Plesiosaurs sailed through the water using four
nearly-equal-sized flippers. No animal alive today uses this
form of locomotion. For a long time scientists were puzzled
as to exactly how these worked. Early theories suggested that
the animals might have used their flippers like oars to "row"
themselves along. This seemed awkward, though, so in the 1970's
paleontologist Jane Robinson decided to take a close look at
just how the muscles must have been attached to the plesiosaur's
flippers. She reached the conclusion that the flippers must
have worked like a set of wings and plesiosaurs literally flew
though the water by flapping their flippers up and down.
Further studies suggested that the plesiosaurs
had very strong muscles for the downstroke, but relatively weak
ones for the upstroke. This has led some scientists to speculate
that the animal would cruise through the water by pushing one
set of flippers down to go forward, while the other set moved
back up to get in position for the next power stroke. They may
have even beat both sets downward together to get a sudden,
short burst of power.
All these sea reptiles shared one characteristic.
They all had lungs, not gills, like fish. That meant they had
to come up to the surface for air. This is another way they
are similar to seagoing mammals of today.
Toward the end of the reign of dinosaurs what
may have been the most ferocious of these sea reptiles arose:
the mosasaurs. These creatures lived after the ichthyosaurs
died out and some scientists think they may have taken their
niche in the ancient sea's food chain.
Mosasaurs, who swam through the shallow sea that
once covered the western United States, had long, tubular bodies.
The tail was often a large fin and the nose a long, pointed
narrow set of jaws with many teeth. Four flippers gave the creature
stability and increased its speed. The largest of these animals,
Tylosaurus, was fifty feet in length with a five-foot
Almost all of the great sea going reptiles died
at the end of the Cretaceous era at the same time the dinosaurs
went extinct. One sea reptile that has survived until today
is the crocodile. Though a bit smaller than the fifty footers
that lived in prehistoric times, the modern "croc" is basically
unchanged in design.
Is it possible that any of these creatures have
survived into recent times to furnish us with tales of sea serpents
or lake monsters? Some of the reports from Loch Ness sound like
a plesiosaur. Some of the stories sailors tell seem to describe
a monasaur. Although it seems unlikely, perhaps some fisherman
in the-not-too distant future will pull in a net to find himself
faced with a live ichthyosaur. Until that happens, if it ever
does, we will have to be satisfied with seeing these magnificent
sea reptiles in pictures.
bones of a Mosasaur.
Oceans of Kansas Paleontology
Stop on Dinosaur Safari
Lee Krystek 1996-2000. All Rights Reserved.