What is the Difference Between
Turtles, Terrapins, and Tortoises?
11 July 1997
Turtles, terrapins, and tortoises are members of the order
Testudines, a division of the class Reptilia.
The primary difference between the three reptiles has more
to do with where they live than actual physical differences.
In fact, use of the three terms varies in different parts
of the world. In the United States, all freshwater, marine,
and most land testudines are known as turtles. The
species of testudines found only in the brackish
waters of marshes and river inlets along the coast is called
a terrapin. Totally terrestrial testudines are tortoises.
Turtles are the most ancient of all living reptiles. They
first appeared on earth some 200 million years ago and have
remained relatively unchanged since that time. The turtle's
survival is most likely due to one of nature's most successful
designs -- the turtle shell. The shell is actually fused
bone, consisting of the turtle's rib cage and spinal cord.
The shells of water turtles are much flatter and more streamlined
than land turtles offering less water resistance during
swimming. All aquatic turtles have webbed feet which help
them displace water with each stroke of their legs.
More than 200 modern species of turtles live in the warmer
parts of the world, populating every continent except Antarctica
and occurring in every ocean except the Arctic. Over two-thirds
of all turtle species live in freshwater.
Twenty species of turtles have been recorded in North Carolina;
all but one, the Box Turtle, are chiefly aquatic. North
Carolina's turtle population includes both the smallest
and largest species in the world. The Bog Turtle, found
in western Carolina, is a rare turtle that only reaches
a length of 3-4". The Leatherback, also rare, is a
sea turtle that attains a shell length of more than 72"
and may weigh up to 1,500 pounds.
Terrapins, often called Diamondbacks because of the angular
rings on their shells, are the only turtles in the world
that live exclusively in brackish water. They have a light
colored neck with small dark markings, a yellow plastron
(lower shell) and webbed feet like freshwater turtles. Female
terrapins are much larger than males, more so than any other
North American turtle.
Tortoises are strictly terrestrial with blunt, clubbed
shaped feet suited for walking on land. Most of the nearly
50 tortoise species live in hot, dry regions of the southern
parts of the world. Their dome-shaped shells and elephantlike
feet with short toes and no webbing differentiate them from
the aquatic turtles and terrapins who have flatter shells
and longer toes joined by a fleshy web. The only tortoise
native to the U.S. is the Gopher Tortoise which can be found
in the sandy-soiled regions of southern South Carolina,
Georgia, Florida, and Louisiana.
Whether aquatic or land dwellers, almost half of the world's
testudines are at risk because of habitat degradation,
hunting, and environmental pollution. In North Carolina,
seven species native to the state, including all five sea
turtles, are considered threatened, endangered, or at risk