Reptiles
2014-2015
Class Reptilia
General Characteristics of Reptiles
•Reptiles are ectothermic, tetrapod vertebrates
•They all possess dry, scaly skin
•Respiration is by lungs only
•Reptiles have a complete or partial 3-4 chambered
heart
•The skeleton is bony with limbs that lift the body off the
ground (except snakes) – limbs are usually paired with 5
digits (pentadactyl)
General Characteristics of Reptiles
(con’t)
•Reptiles are dioecious and fertilization is always internal
•No larval stage
•The great majority of reptiles are carnivorous although certain
turtles & lizards are omnivores or herbivores
•Found in many kinds of habitats, from freshwater, salt water, to
the driest of deserts. The chief factor that limits their distribution
is temperature
Class Reptilia
•Approximately 7000
living species (300 in
the US)
•There are 4 living
orders of reptiles and
15 extinct orders
• (dinosaurs)
Characteristics that distinguish
reptiles from amphibians
•Reptiles have tough, dry skin that offers protection against
desiccation that is shed periodically
Characteristics that distinguish
reptiles from amphibians
•The shelled (Amniotic) egg of reptiles contains food and
protective membrane for embryonic development
Characteristics that distinguish
reptiles from amphibians
•Reptilian jaws are designed
for applying force to grip
or crush prey. Jaw muscles
are much larger & longer
Characteristics
All reptiles have some form of copulatory organ for internal
fertilization. This is a requirement of a shelled egg because the sperm
must reach the egg before it is enclosed in a leathery covering
Characteristics that distinguish
reptiles from amphibians
•Reptiles have a more efficient circulatory system and higher
blood pressure than amphibians
•Reptile lungs are better developed than amphibians. Reptiles
depend on lung respiration exclusively and skin breathing has
been abandoned.
Characteristics that distinguish
reptiles from amphibians
•Reptiles have evolved efficient strategies for water
conservation. Nitrogenous wastes from the kidneys are excreted
as uric acid crystals
•Instead of urea or ammonia, so the urine of most reptiles as a
semi-solid paste
Uric Acid Crystals
Characteristics that distinguish
reptiles from amphibians
•Reptiles have better body
support and more efficiently
designed limbs for travel on land
Characteristics that distinguish
reptiles from amphibians
•Reptilian nervous system is much more complex than amphibians.
Increased size of the cerebral cortex allows for higher levels of
thinking.
Order Testudine (meaning a tortoise)
approximately 330 species little
changed in 200 million years; dinosaur
turtle called Archelon
General Characteristics
•
•
•
•
•
Enclosed in a shell consisting of a dorsal carapace (ribs &
vertebrae) and a ventral plastron (sternum)
The shell is composed of an outer horned layer of keratin and an
inner layer of bone
Turtles have a poor hearing but a good sense of smell, acute vision
and color perception as good as a human
Turtles vary widely in size with the largest weighing 900 kg. and
because of their low metabolism they can live more than 120 years
Turtles lack teeth but have horned beak for gripping and tearing
food
Reproduction
 Turtles are oviparous with
internal fertilization
 Amniotic eggs are buried in
the ground. In most turtle
species, temperature
determines the sex of the
hatchlings – low
temperature produces males
and higher temperature
produces females. All
temperature-dependent
reptiles lack sex
chromosomes
Size & Age
 The giant marine turtles may reach 2 meters in length and
725 kg in weight
 Low metabolic activity may explain their longevity, believed to
exceed 150-200 years. Even the common Box Turtles live
over 30-40 years
Order Squamata
 Order Squamata (means Scaly) examples are snakes & lizards
 Largest group – 95% of known living species
 2 main suborders: Lizards & Snakes
Order Squamata
 Suborder Lacertilia (lizards) – 3300 Species
 Examples are geckos, iguanas, skinks, chameleons & monitors

General characteristics
o Have moveable eyelids
o Teeth present in some species
o Scales or epidermal plates
o Secrete a highly crystallized uric acid to conserve
water
o Lizards may deliberately cast off their tails to avoid
capture, this adaptation is called autotomy
o Lizards store fat in their tail to survive drought
Order Squamata
 Suborder Lacertilia (lizards) – 3300
Species
 Examples are geckos, iguanas, skinks,
chameleons & monitors

2 Poisonous species in North America
o Gila Monster which is found in the
SW area of USA
o Beaded Lizard which is found in
Mexico
o Poison is secreted by the lower jaw;
lizards do not have fangs
o These species are not lethal to
humans
Gila Monster
Beaded Lizard
Order Squamata
 Suborder Lacertilia (lizards) – 3300 Species
 Examples are geckos, iguanas, skinks, chameleons & monitors
 Body Size
 Largest is the monitors with the Komodo dragon growing to 12 feet in
length
 Smallest are the chameleons of Europe @ 4 cm in length
Order Squamata
 Suborder Lacertilia (lizards) – 3300 Species
 Examples are geckos, iguanas, skinks, chameleons &
monitors
 Other species include –
 Iguanas – this group includes the common green iguana,
the horned toad which used to be common in
Oklahoma and now is considered endangered;
Marine Iguanas of the Galapagos Islands which have
developed oceanic feeding behaviors
 Chameleons – have distinctive adaptive behavior to
color change due to chromatophore cells in the skin
Order Squamata
 Suborder Lacertilia (lizards) – 3300 Species
 Examples are geckos, iguanas, skinks, chameleons & monitors
 Other species include –
 Skinks – 14 species live in the USA. Have flat overlapping scales that give a
shiny, smooth appearance
 Geckos – small agile and nocturnal with adhesive toe pads that allow them to
walk on ceilings
Blue Tailed Skink
Order Squamata
 Suborder – Serpentes
 ( to creep ) – snakes
 2300 species, most
widespread of all reptiles
 General characteristics of snakes
–


Snakes are entirely limbless
Skull is highly kinetic which
enables them to eat prey
several times their own
diameter. The lower jaw is
loosely hinged and the 2
sides of the mandible are
only connected by muscle and
skin
Order Squamata
 Suborder – Serpentes ( to creep ) – snakes
 2300 species, most widespread of all reptiles
 General characteristics of snakes –
 The opening (trachea) to the respiratory system is positioned far forward
between the mandibles so that the snake can breath while swallowing
large prey
Order Squamata
 Suborder – Serpentes (
to creep ) – snakes
 2300 species, most
widespread of all reptiles
 General
characteristics of
snakes –
 The cornea of a
snake’s eye is
covered by a
transparent
mambrane called
the spectacle
Order Squamata
 Suborder – Serpentes (
to creep ) – snakes
 2300 species, most
widespread of all reptiles
 General characteristics of
snakes –
 Snakes have a special
sense organ called
Jacobsen’s Organ
which are pits in the
roof of the mouth, the
tips of the forked
tongue fit into these
pits and the scent
information is
transmitted to the brain
Snake Movements – 4 types
 Lateral undulation –s-shaped – pushes against rough
ground or water
 Concertina – accordion pleats – folds body & thrusts
head forward
 Rectilinear – Straight ahead – head lifted – muscle
contracts thrusting the head forward (example –
Boas)
 Sidewinding – sideways looping used by desert vipers –
only 2 parts of the body in contact with hot sand at
any time
See Page 559 – Figure 26-21
Snake Movements
http://animal.discovery.com/videos/whats-to-love-sidewinder-snake.html
(Sidewinder)
http://www.bing.com/videos/search?q=rectilinear+snake+motion&view=detail&mid=B
2A5685F9E484BC44F36B2A5685F9E484BC44F36&first=0&adlt=strict
(Rectilinear)
 Snakes kill their prey by a variety of methods
 Non venomous snakes use suffocation to subdue prey
 The Boas and Pythons use this method
 Other non venomous snakes that eat specific prey may just
bite and swallow; snakes such as bull snakes use this
method
 Venomous snakes use one of two types of toxins
 Neurotoxin acts mainly on the nervous system and
paralysis results, shutting down the respiration or heart
beat
 Hemotoxins break down red blood cells and vessels
and result in extensive hemorrhaging of blood into the
tissues
 Poisonous snakes are divided into four families (based on fang
type)
 Family Viperidae have highly developed retractable fangs at the
front of their mouth. This group includes the pit vipers which
have heat seeking pits on the front of the rostrum
 Examples – rattlesnakes, copperhead, and water moccasin
 Poisonous snakes are divided into four families (based on fang
type)
 Family Elapidae have short permanently erect fans and inject
poison by repeated bites
 Examples are: coral snakes, cobras, black mamba
 Poisonous snakes are divided into four families (based on fang
type)
 Family Hydrophiladae are the most high poisonous of all snakes
 Example: sea krait
 Poisonous snakes are divided into four families (based on fang
type)
 Family Colubridae; this is a very large group and includes most of
the non-poisonous snakes but there are 2 deadly snakes in this group
and they are rear fanged snakes that use their poison to quiet
struggling prey
 Examples: African boom-slang & twig snake
 Antidote for snake bite is called antivenin
 Produced by antibodies in the blood from snake bitten
or venom injected horses
 Antibodies must be specific for the snake bite
 The total human death toll from snakebite is about 25,000
each year
 The toxicity of a venom is measured by the median
lethal dose on laboratory animals, according to this
standard, the sea snakes and the venom of the
Australian tiger snake appear to be the most deadly
but there are more dangerous snakes because of their
aggressiveness such as the king cobra (exceeds 5.5 m in
lenth) these snakes cause more than 9,000 deaths each
year
Collection of Snake Venon
http://www.bing.com/videos/search?q=collecting+snake+venom
&view=detail&mid=AB3A2A77F7362195ED9FAB3A2A77F736219
5ED9F&first=0&adlt=strict
http://www.bing.com/videos/search?q=collecting+snake+venom
&view=detail&mid=AB3A2A77F7362195ED9FAB3A2A77F736219
5ED9F&first=0&adlt=strict
 Reproduction –
 Most snakes are oviparous
 The pit vipers are ovoviviparous ( this includes all
poisonous American snakes)
 The sea snakes are viviparous – live / placental
young
Order Rhynocephalia (2 living species)
the common name is Tuatara
 Slow growing animals with a very long life
 (Over 80 years)
 Many features identical to Mesozoic fossils that are 200
million years old
 Has a 3rd eye (pineal eye) with cornea, lens and retina – the
function of this 3rd eye is unknown
Order Rhynocephalia (2 living species)
the common name is Tuatara
 Still called by its dinosaur name sphenodon; this animal shows
the slowest rate of evolution known among the vertebrates
 Has no eyelids
 Has hooks on its ribs like birds
 Males have 2 penises
Order Crocodilia (crocodiles & alligators
25 species
 Have remained virtually unchanged for millions of years
 There are 3 distinct groups
 Crocodiles
 Alligators
 And the Gavials – found in India
 Have a complete secondary palate that allows them to breathe while
swallowing food
 Alligators are much less aggressive than crocs. The Nile crocodile can
grow to over 4000 lbs. and have been known to kill cattle.
 They are oviparous and the sex of the offspring is temperaturedependent. High nest temperatures produce males and low nest
temperatures produce females and this can result in females
outnumbering males 5 to 1
Comparison of Crocodiles & Alligators
Crocodiles
Alligators
Narrow Head
Broad Head
Pointed Snout
Rounded Snout
VisibleTeeth when mouth is closed
Hidden Teeth when mouth is closed
More Aggressive
Less Aggressive