Across vs Tortoise,” 2017). The classification of tortoises

Across the globe there are more
than 300 different types of turtles and has existed for more than 200 million
years. Turtles can be classified on the foundation of their behaviors and
physical structures. The largest turtle in the world is the leatherback sea
turtle, the smallest turtle is the speckled padloper tortoise. The leatherback
sea turtle weigh about two thousand pounds and has a shell length of 6.6 feet.
Whereas the speckled padloper tortoise weighs about five ounces with a length
of 3.1 inches. A very unique characteristic to a turtle is the shell. The
turtle has so many other parts connected to their shells that you would have
never known, such as ribs. The shell is used for protection from predators and
many different objects (“Different Types of Turtles,”

Turtles are reptiles that come from
the testudines order, which is divided into fourteen families. Altogether about
97 genera of the species reptiles. Turtles are split up into two suborders
Cryptodira and Peurodira. The suborder Cryptodira consists of 11 families and
Puerodira consists of three families (“Different Types of Turtles,” 2017).

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What is the difference between
turtles and tortoises? The difference is that tortoise reside on land and
turtles reside in the water. Not every turtle lives in the water but just about
all of them do. They are both reptiles from the order Testudines, but are in
different families. Tortoises are mostly found in Asia, Africa and some are
found in America as well. Their lifespan is 80-150 years. The longest living
tortoise is 326 years (“Turtle vs Tortoise,” 2017). The classification of
tortoises is Kingdom: Animalia, Phylum: Chordata, Class: Reptilian, Order:
Testudines and Family: Testudinate. Their shell is shaped like a large dome
with some having bumps on top. The bumps on the shell are in only in some
species. The shells are heavier than a turtle shell. Their feet are short with legs
that are sturdy and bent. Tortoises are herbivores, but depending on the
species they prefer live food. Soon after birth the tortoise hatchlings move
from their nest to the mother’s burrow  (“Turtle
vs Tortoise,”2017).

Turtles are mostly found in Africa
and America. The lifespan is 20- 40 years and the oldest was 86 years. The
classification of a turtle is Kingdom: Animalia, Phylum: Chordata, Class:
Reptilian, Order: Testudines and Family: Testudinate. Their shells are mostly
streamlined, flat and generally light- weight. Turtle feet are webbed with long
claws. The diet of turtles is labeled as omnivores. They eat fruits, veggies,
leafy vegetation and meat. For 90-120 days the turtle hatchlings stay in their
nest on their own (“Turtle vs Tortoise,” 2017).

The shells of the tortoise and
turtle that cover their bodies are very important because they give researchers
a good idea of how they live. The turtle shell is made flat and streamlined so
that they are able to swim and dive, while the large dome shaped tortoise shell
provide protection from predators. Moreover, the lightness of the turtle shell
helps avoid them from sinking and also increase the speed of their swimming (“Turtle
vs Tortoise,” 2017).

The bodies of tortoises and turtles
are covered by a shell, the upper part of the shell is known as the carapace
and the lower part is known as the plastron. The carapace and the plastron are
attached by a bridge. Even though the head and limbs are able to be withdrawn
from the shell, the whole body could never be totally detached from it. In
nature the reptiles are very reserved and shy (“Turtle vs Tortoise,” 2017).
These two parts of the shell are very different due to the different bones
associated with them and the different formations that are contained in them.
The carapace contains the ribs, vertebral column, the dermal and epidermal
layers of the shell. There are ten vertebrae and single ribs that extend out
and into the dermis. (Gilbert 47).  The ribs which enter
into the layer of the carapace known as the dermal layer, contains many
different bones. Turtles neural and costal bones are located in the dermal
layer. The neurals are associated with the vertebrae, while costals are
associated with the ribs. Attached to each of the thoracic vertebrae are the
neurals. The first neural is attached to the nuchal bone of the shell while the
other is attached to the anterior pygal. Costals with a total of 8 are
organized in pairs, associated with a rib or multiple ribs, and are suturally
connected to its neighboring costal. The first costal is connected with the
first and second ribs, while the ninth and tenth ribs are connected to the last
costal. (Gilbert 48).

The bottom half of the shell known
as the plastron, is the fusion of bones including the collar bones. The
plastron also includes the bones that are between the collar bones and parts of
the ribs. Compared to the carapace the plastron only has nine bones, while
there is a total of 50 bones in the carapace (“Anatomy
and Diseases of Turtle and Tortoise Shells,” 2017).  The plastron consists of paired and unpaired
bones. Epiplastra are paired bones similar to the ones in tetrapod’s (Gilbert 48).  With one unpaired bone the entoplastra, which
would be equal to an interclavicle in a tetrapod. A long the side of the turtle
there is a bony bridge that joins the carapace and plastron. Usually in the
plastron there is a moveable joint that act as hinge to allow the turtle to
pull the parts together tightly. As this is happen the turtle is retracting its
body into the shell. Shells have a blood and nerve supply. If the shell becomes
injured, it can result in bleeding and pain (“Anatomy and Diseases of Turtle
and Tortoise Shells,” 2017).  

What are turtle shells covered
with? They covered with keratin, which are arranged in patches known as scutes
or shields. There about 38 scutes on the carapace and twelve to fourteen on the
plastron. The names and numbers of the scutes roughly correspond to the
adjacent bones and body portions. The scutes, however, do not precisely overlap
the bones. Instead, they are staggered, which helps give the shell more
rigidity. There may be fewer bones in some aquatic carapaces and instead of
having scutes they will have leathery skin. Related to the habitat each species
will differ in shell shapes. Being aquatic turtles having a flatter shell while
tortoises have dome- shaped carapace (“Anatomy and Diseases of Turtle and
Tortoise Shells,” 2017).  

The number of scutes usually does
not change, but their size does as the shell is growing. Sometimes in older
turtles the old scutes will shed and larger and newer ones will replace it.
However, keratin is laid down in other species, scutes will enlarge in
diameter. Experts have been using scutes as they call “growth rings”, to
determine the age of a turtle. Age estimation based on growth layers, however,
can be erroneous for several reasons: Some turtles produce multiple growth
zones per year. Growth is determined by changes in the environment (seasons),
so age determination by examination of growth rings would be more accurate in
wild turtles, than those kept in environments which do not change
significantly. Growth layers may wear with age, so older turtles may be estimated
to be younger than they really are (“Anatomy and Diseases of Turtle and
Tortoise Shells,” 2017).  

There are different diseases
dealing with the turtle shell. “Dysecdysis” is the term to describe
the condition in which an old scute is retained and not shed properly. This
condition is often associated with poor husbandry, and may occur if the turtle
has not been able to dry off or bask sufficiently to lose its old scutes.
Retained scutes often become infected. A turtle with dysecdysis should be
examined by a veterinarian. Sulcata tortoise with malformed scutes (“Anatomy
and Diseases of Turtle and Tortoise Shells,” 2017).  

A turtle with an inadequate calcium
or Vitamin D intake, inadequate exposure to ultraviolet light, or disease of
the liver, kidneys, or parathyroid glands may develop metabolic bone disease.
This causes softening and malformation of the bones. The shells of turtles with
metabolic bone disease are often deformed, with the rear area of the carapace
pulled downward, and the marginal scutes pulled upward. Tortoises with
metabolic bone disease may develop pyramid-shaped scutes. Metabolic bone
disease can be fatal; turtles suspected of having this disease should be
examined by a veterinarian. Husbandry and diet changes may be able to correct
the calcium imbalance, but deformities are generally permanent. Pyramiding, or
pyramidal growth syndrome is a condition in which the scutes take on a conical
shape. This condition has been associated with feeding excessive protein,
inadequate calcium, low fiber, and other dietary excesses or deficiencies (“Anatomy
and Diseases of Turtle and Tortoise Shells,” 2017).  

Although rare, renal failure in a
turtle has been reported to cause a turtle to slough his scutes. Kidneys help
to maintain the proper calcium and phosphorous levels in the blood. If the
kidneys fail, the phosphorous level in the blood increases. The turtle’s body
attempts to compensate by moving calcium from the bones into the blood stream.
The bones in the shell, then, can become soft.     
Ulcers of the shell may be superficial or deep, and may be termed “shell
rot.” Ulcers are generally a result of poor husbandry. Turtles with
ulcerative shell lesions should be examined and treated by a veterinarian, as
the ulcers may become infected and penetrate through the shell. The shell will
need to be cleaned daily, and dead tissue removed. Topical and/or injectable
antibiotics are required in the case of bacterial infections. Deep ulcers may
need to be repaired through surgery and the application of acrylic or
fiberglass material. In a disease called “septicemic cutaneous ulcerative
disease,” or SCUD, ulcers may be seen on both the shell and legs. This
condition is often associated with the bacteria, Citrobacter freundii (“Anatomy
and Diseases of Turtle and Tortoise Shells,” 2017).  

Injuries due to trauma, animal
bites, or burns can cause pain, can lead to infections, and may cause misshapen
scutes as they heal. Although the shell has a remarkable ability to repair
itself, any turtle with an injury to the shell should be examined by a
veterinarian immediately. Fatal infections can occur. Other causes of deformed
scutes: Scutes may also be deformed in size or shape due to genetics or
improper egg incubation. The shell of a turtle is an amazing adaption which has
allowed turtles to exist for millennia. The proper diet, husbandry, and care
are vital to maintain a healthy shell (“Anatomy and Diseases of Turtle and
Tortoise Shells,” 2017).  

The turtle shell is actually a
peculiar evolution of a turtle’s bone structure. Its vertebrae, pelvis,
ribcage–it has no muscles between its ribs, which makes this easier–and other
bones fuse together to form a sort of reptilian exoskeleton. The scale-like
pieces which make the turtle shell look like a soccer ball are called scutes,
and they have individual names, often based on location, after what they’d be
called in a less bizarre animal (anal scute, pectoral scute, that kind of
thing) (Nosowitz, D. 2013)

The turtle shell isn’t like any
other protective element of any living animal: it’s not an exoskeleton, like
some invertebrates have, nor is it made of ossified scales like armadillos,
pangolins, or some snake and reptile species. It’s not made of skin. It can’t
be removed to do so would kill the turtle, and all that’s underneath is
internal organs. Around 240 million years ago, living in a large lake, in a
fairly warm, subtropical climate early turtle didn’t have the same shell as
modern turtles today. With a length of 8 inches long, slender legs, long neck
and tail and a weird trunk region that is boxy. This turtle was named Pappochelys.  Greek for “grandfather turtle.”  (Greenfield Boyce, N. 2015)

Pappochelys looked
quite different than the turtles and tortoises of today, however. The animal
had no shell, but it did have what appear to be the makings of one. Its ribs
are broad and sturdy, and they fan out from the spine, a physiological set-up
that the researchers suspect evolved not only for protection but also as a
“bone ballast” a way for the animal, which was likely aquatic or semiaquatic,
to better control its buoyancy. That wasn’t the only hint of what would eventually
become turtles’ trademark feature: Pappochelys also has a line
of hard, almost shell-like bones along its belly (Nuwer, R. 2015).  The turtle
creature has the real beginnings of the belly shell developing, little rib-like
structures beginning to fuse together into larger plates. What’s more, the
fossil has two openings in the skull behind the eye sockets. That’s important
because it suggests that turtles are closely related to the reptile lineage
that gave rise to lizards and snakes. Researchers had previously thought that
turtles evolved from a different group of primitive reptiles that are now
extinct. While other animals have developed bony plates of various kinds, Sues
says, to be “completely enclosed basically, in its own little bony house
is something that’s unique to turtles.” (Greenfield
Boyce, N. 2015).

In conclusion, a fossil that is about 214 million years old shows a
creature known by everyone as a turtle, was the first turtle to fully develop a
shell. “Early on, you first make broad ribs,” Sues explains.
“Then you build the belly shell. Then you complete the back shell. And
then you have basically what’s a modern turtle.” “I think the classic
idea has always been that the shell evolved for protection,” Lyson says.
But he points out that ribs play a vital role in breathing, and using ribs to
create a shell meant that turtles had to come up with an entirely new way to
get air in and out. “Why lock up your ribs into a shell? No other animal
does that.” Turtles shell has multiple purposes (Greenfield Boyce, N. 2015).






                                                           Work Cited

Anatomy and
Diseases of Turtle and Tortoise Shells. (n.d.). Retrieved November 12,
2017, from

Gilbert, Scott F., Grace A. Loredo,
Alla Brukman, and Ann C. Burke. “Morphogenesis of the Turtle Shell: The
Development of a Novel Structure in Tetrapod Evolution.” Evolution and
Development 3.2 (2001): 47-58. Web.

N. (2015, June 24). How The Turtle Got Its Shell. Retrieved December 03,
2017, from

M. (2017, March 12). Different
Types of Turtles. Retrieved November 12, 2017, from

D. (2013, June 03). How The Turtle Got Its Shell. Retrieved December 03,
2017, from

Nuwer, R.
(2015, June 24). This Ancient Creature Shows How the Turtle Got Its Shell.
Retrieved December 03, 2017, from

Strauss, B. (n.d.). The Slow, Slow,
Slow Story of Turtle Evolution. Retrieved December 03, 2017, from

Turtle vs
Tortoise. (n.d.). Retrieved November 12, 2017, from

Turtle vs. Tortoise.
Retrieved from


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